Category: seasons

Bumblebees who brave the winter

Posted on by andy.winfield

By Nicola Temple

This past weekend, my family and I met with friends in the village of Shipham, in Somerset, for a walk. It was torrential rain, yet we were determined. We dressed ourselves and three children under the age of 10 in waterproofs and set out. We arrived at a local country pub, not more than 3 km away, resembling drowned rats. And as a Canadian living here in the UK, I still marvel at the fact that nobody took one bit of notice at the state of us. It’s what you do. You get wet. You find a pub. You hunker down for a hot Sunday lunch. And you hope it tapers off before you have to head out again. (It didn’t.)

Pollinators, at least of the flying insect variety, aren’t terribly keen on this kind of weather either. Most hunker down for the winter months as there is generally not a lot of nectar to forage this time of year anyway. How they do this depends on the species. Honeybees reduce the colony to a minimal size and rely on their honey stores to see them through, while they dance in order to regulate the temperature of the hive. Most bumblebee colonies die out completely and the queens that mated at the end of the season find a place to hibernate. Solitary bees may hibernate as adults or as larvae, emerging only when the weather conditions are suitable. To each their own.

Martin Cooper spotted this buff-tailed bumblebee queen
foraging on his Mahonia flowers in Ipswich on a sunny
January day in 2015.
Photo credit: Martin Cooper [via Flickr CC]

However, there is one flying pollinator that can be spotted this time of year here in Bristol, and indeed, other warmer regions of the UK. It is the common buff-tailed bumblebee (Bombus terrestris). This species was first spotted during the winter of 1990, in Exeter. Sightings have been increasing ever since and include nest-founding queens, workers and males, suggesting this is a winter generation of the species.

The mated queen will emerge from her subterranean dormant state (diapause) during warm winter weather and set about establishing a new colony. The potential cost of waking up early is that the warm weather could be short-lived and temperatures could plummet. The benefit, of course, is that there’s nobody to compete with for food. If successful, the queen can establish a colony before the other pollinators even wake up from their winter nap.

Introduced plants provide winter forage

Of course, there is potentially another cost to emerging early – there could be nothing to eat. Bees are able to forage at temperatures around 0oC, but if there aren’t enough plants in flower, they won’t find the pollen and nectar needed to sustain the colony. Few native UK species flower in winter, but species introduced by avid gardeners to bring some winter colour to the garden, also bring some much-needed food to the buff-tailed bumblebee.

Researchers at Queen Mary University of London and The London Natural History Society, conducted a study of buff-tailed bumblebees foraging in London parks and gardens during winter about ten years ago. They wanted to see just how much food the bees were finding as food is directly related to the success of the colony.

The researchers found that there was plenty of forage to sustain the colonies and, in fact, the foraging rates they recorded near the end of winter were equivalent to peak foraging rates found in the height of summer. This doesn’t mean that the winter-flowering plants, such as the evergreen shrubs of the Mahonia spp., are providing more pollen and nectar than all the plants in the height of summer. But it does mean that each flower might have more pollen and nectar available because there aren’t other pollinators out and about also using the resource. The bumblebees, therefore, don’t need to go as far to find an equivalent amount of food and so they can collect it at a faster rate.  

Strategies for tolerating cold

Buff-tailed bumblebees aren’t as tolerant to cold as some other bee species; workers will freeze solid at about -7.1oC while queens freeze at -7.4oC. The bumblebees can obviously find warmth in the colony, but they need to forage and therefore be able to tolerate short spells of cold during the winter months. They may even need to tolerate cold temperatures for up to 24 hours as bumblebees often overnight away from the colony when they are unable to return from foraging.

Researchers from the University of Birmingham looked at the different cold tolerances of this bumblebee species a few years ago. They found that 50% of workers died after being exposed to 0oC for 7.2 days while queens could last over 25 days at this temperature – likely due to their fat reserves. However, as the forage study showed, the bees seem capable of finding food sources closer to the colony during winter months, which may reduce the likelihood of them having to endure cold temperatures for a lethal period of time.

These bumblebees may also have adopted some strategies to help reduce their possibilities of freezing. Pollen is an ice-nucleating agent in that it promotes the development of ice at higher temperatures. Other insects have been observed to expel any ice-nucleating agents from their gut when they experience low temperatures to avoid freezing. While this wasn’t observed in the bumblebees, it is a strategy that individuals might employ when caught out in the cold.

The more frequent observation of buff-tailed bumblebees in winter is thought to be a result of warmer autumn temperatures brought about by climate change. In a study from 1969, researchers reported a 6-9 month dormancy of all bumblebees in southern UK, so in a relatively short period of time there has been a considerable change in their seasonal pattern. There seems to be some flexibility in these patterns among bumblebees and for now, establishing winter colonies seems to be working for the buff-tails. However, with so many of our pollinators under threat, there is obviously also concern among the scientific community that more frequent extreme weather events could also spell disaster for these colonies that have selected to brave the winter months. As gardeners, we can perhaps do our bit by planting some winter forage species.

This year, the University of Bristol Botanic Garden will embrace a pollinator theme, with the aim of highlighting some of the lesser-known pollinators that are so important here in the UK. We love our pollinators, but research is still revealing so much about their unique and complex relationships with plants. So watch this space as we share some of these wonderful stories through our blog. We will also be posting pictures of pollinators we see in the Botanic Garden on our Twitter feed and Facebook page. But to see these pollinators in action, take some time to visit the Botanic Garden. Make space in your busy schedule to watch nature at its best – it’s worth it.

Sources:

Alford DV (1969) A study of the hibernation of bumblebees (Hymenoptera: Bombidae) in Southern England. Journal of 
     Animal Ecology 38: 149-170.
Owen EL, Bale JS, Hayward SAL (2013) Can winter-active bumblebees survive the cold? Assessing the cold tolerance of 
     Bombus terrestris audax and the effects of pollen feeding. PLoS ONE 8(11): e80061.          
     doi:10.1371/journal.pone.0080061
Stelzer RJ, Chitka L, Carlton M, Ings TC (2010) Winter active bumblebees (Bombus terrestris) achieve high foraging 
     rates in urban Britain. PLoS ONE 5(3): e9559. doi: 10.1371/journal.pone.0009559 

‘Tis the season…or is it?

Posted on by andy.winfield

By Helen Roberts

As I sit at my desk this morning, staring out the window, the weather is dire. There is slanting torrential rain and high winds, a typical December day perhaps.
Here in the UK, the seasons are changing and we are experiencing extremes of weather. For example, we have had wetter, milder winters in the southwest over the last couple of years along with increased flooding, particularly on the Somerset Levels. And then there was the very slow start to spring this year, with temperatures well below average in April. This was followed by a very hot end to the summer and warmer-than-average temperatures throughout autumn.
These changes to the seasons are linked to global climate change and are throwing the UK’s wildlife into disorder and affecting the fine balance of habitats and ecosystems. This is not a good scenario for biodiversity in the UK. Seasonal timing is off. When seasons start and end is shifting, and the length of the season itself is changing, making ‘growing seasons’ a more fluid concept. There is also increased risk for most gardeners of a ‘false spring’. Many plants and animals are changing their geographical ranges in order to adapt to these changes.
One of the most significant effects has been the disruption of lifecycle events and these are manifesting themselves in different ways. Bird migration, insect emergence, incidence of pests and diseases and flowering times are being thrown out of kilter.  
Researchers from the University of East Anglia recently analysed 37 years worth of data from the UK Butterfly MonitoringScheme (UKBMS) and found that extreme weather events were causing population crashes of butterflies. Uncommonly high rainfall events during the cocoon life stage affected 25% of UK butterfly species. And more than half of species were affected by extreme-heat during the overwintering life stage, possibly due to the increased incidence of disease or the effect of a ‘false spring’, causing butterflies to emerge too early only to be decimated by a return to cooler temperatures.
Warm temperatures are not all bad for butterflies though, as they will benefit from hot temperatures over the summer months when they are in their adult form and resources are plentiful. However, if populations crash more frequently than they expand, these extreme weather events could threaten UK butterflies.
The spider orchid (Ophrys sphegodes).
Photo: Jacinta Iluch Valero via Flickr [Creative Commons]

Changes in seasonal timing are also knocking the relationships between plants and animals out of sync, including the delicate balance between plants and pollinators. Thiscan be detrimental to the balance of entire ecosystems. An elegant study carried out by scientists from Kew and the University of East Anglia found that earlier springs brought about by rising temperatures are affecting the relationship between a rare spider orchid (Ophrys sphegodes) and its sole pollinator, the solitary miner bee (Andrena nigroaenea).   

This particular orchid has a flower that resembles and smells like a female miner bee and it uses this deceit in order to lure the male miner bee in. The male attempts to mate with the flower and by doing so, pollinates the flower. The plant has evolved to flower at the same time as the male bees emerge, but before the females do.
What the researchers discovered, by looking at the data set going back to 1848, was that rising temperatures are causing the relationship between orchid and bee to break down. Although rising temperatures cause both the bee to emerge and the orchid to flower earlier, the effect on the bees is much more pronounced. The male bees emerge much earlier and the orchids now flower as the female bees emerge. This means the males are not “pseudocopulating” with the flower because the real thing is already available and so the rare spider orchid is having fewer pollinations.
However bleak this picture may seem, plants and animals do have the ability to adjust to seasonal changes caused by climate change, it is just whether they can adapt quickly enough for these intricate ecological relationships to remain intact.
Helen Roberts is a trained landscape architect with a background in plant sciences. She is a probationary member of the Garden Media Guild and a regular contributor to the University of Bristol Botanic Garden blog.


References

Latecomers to the summer flowering party

Posted on by andy.winfield

By Helen Roberts

It’s the time of year when most people think that gardens are nearing the end of the full flush of summer blooms. Mid summer flowers may be dwindling but there are numerous late flowering species that still provide a riot of colour. I have always been interested in gardens at this time of year because we are often rewarded with a spell of bright sunny weather in autumn. I want to be outside enjoying the garden, hanging onto the summer for as long as I can before the cold deepens and the nights draw in. So planning for some autumn colour in the garden can be very rewarding.
  
With thoughts of designing my own garden for a prolonged season of flowering, an excursion to the University of Bristol Botanic Garden was due. I met up with Froggie who showed me the bounty of colour at this time of year in the gardens.
First stop was the hot borders which can be found in front of The Holmes, which were evidently at their most scorching in terms of vivid colours, with swathes of Hemerocallis, Penstemon, Helenium, Rudbeckia, Tithonia, Fuchsia and Dahlia. Froggie pointed out the lovely Verbena bonariensis, which is such a great plant for pollinators and one that self seeds profusely. Verbena adds some soft architectural form to borders and provides flowers for months on end. A plant that I was less familiar with was the rather cute and tender Cuphea cyanea or Cigar flower with red and yellow tipped flowers. There is also another variety of Cuphea called the Pink Mouse – each flower does look like a miniscule mouse!
Providing structure to the hot borders were the awesome sub tropical Abyssinian Banana (Ensete ventricosum), which were still looking amazing but will soon be lifted and taken into the greenhouses. The staff keep a close eye on the weather at this time of year, any sign of frost forecast and they must move quickly to take in the tender species.
Froggie explained, “We had some hard winters a few years back and we lost quite a lot of plants so lifting plants into the greenhouses ensures they are protected. They are our insurance against a very cold winter.”
Salvia uliginosa can be found flowering this time of year
by the Botanic Garden’s main pond.
Photo credit: Helen Roberts.
Many of the shrubby salvias are in this tender category. Froggie showed me Salvia confertiflora, an exotic late flowering species with beautiful fuzzy crimson inflorescences about 0.5m tall. This will be moved inside soon when the weather cools. Another that caught my eye in the pollinator beds located on one side of the main pond was Salvia uliginosa, a very tall plant with vibrant sky blue inflorescences that were buzzing with bumblebees.
I have to admit to an obsession with shrubby salvias, which started after many visits to the garden of plant guru Derry Watkins over the course of this summer. Her passion for these beautiful plants is contagious. They are an extraordinary group of plants that flower continuously from June until October and the flower colours are exquisite. The colours really pack a punch in terms of vividness. I purchased Salvia microphylla ‘Cerro Potosi’, which started producing vibrant magenta flowers back in June and is still putting on a show of pink in October. I plan to take cuttings of this to provide a back up plan in case I lose my original plant (I am going to risk leaving mine out over winter).
Toad Lilies (Tricyrtis macropoda). Photo credit: Helen Roberts.
In amongst the buzzing pollinator borders were the very pretty and delicate Toad Lilies (Tricyrtis macropoda). I watched bees visiting these inflorescences and collecting nectar by robbing it through the back of the flowers. The pink flowered society garlic (Tulbaghia violacea) and Japanese Anemone (Anemone hupehensis) were very subtle in hue combined with dazzling yellow Rudbeckia and deep purple drooping flowers of Agapanthus inapertus ‘Midnight Cascade’. Many of the hummingbird-pollinated plants were in flower including the pineapple relative Ochagavia litoralis and the terrestrial bromeliad Fascicularia pitcairnifolia. The latter, at present, is visually screaming, “Come pollinate me!” with the centre of the rosette turning an intense scarlet with a dense cluster of blue flowers tipped with bright yellow pollen.
Throughout the gardens, as I toured around with Froggie, there were interesting flowering species and the colours varied tremendously from vivid red and pink to deepest indigo. The flower forms were diverse too; delicate dangling umbels, ‘in your face’ discs of blooms, hooked and lipped nectar-rich inflorescences and some which were just plain weird looking. The gardens simply still looked stunning and I left knowing that it’s not yet time to put gardens to bed, there’s plenty more flowers to come.
More species that are flowering now in the garden include:
  • Abutilon sp. (Chinese lantern)
  • Agastache sp. (Giant hyssop)
  • Campsis sp. (Trumpet vine)
  • Caryopteris x clandonensis (Bluebeard)
  • Colchicum agrippinum
  • Commelina tuberosa Coelestis Group (Day flower or Sleeping Beauty)
  • Crinodendron hookerianum (Chilean lantern tree)
  • Erica tetralix (Cross-leaved heath)
  • Impatiens tinctoria
  • Lantana camara (Yellow sage)
  • Liriope muscari (Big blue lily turf)
  • Tropaeolum peregrinum (Canary creeper)
  • Verbena peruviana (Peruvian verbena)

Branching out on your choice of Christmas tree

Posted on by andy.winfield

By Helen Roberts

Nothing quite captures the Christmas mood more than seeing a beautifully decorated Christmas tree. Whether you choose to adorn one yourself or not, the Christmas tree is decorated and celebrated in many different countries and different nations have their own favourite species. 

The foliage of the Balsam Fir.
Photo by Robert H. Mohlenbrock @ USDA-NRCS 

I am particularly picky about the species of tree our family have and the overall shape of the tree. This fussiness stems from spending time living in Canada; high standards were set when our first Christmas tree was a wonderfully large and fragrant Balsam Fir (Abies balsamea), with its dark green, long lasting foliage. This tree is a very popular species used in North America for Christmas, and on our return to England I tried to find a nursery to buy a Balsam Fir for Christmas without luck. I did some research and eventually found a similar species, but also found out some interesting information about our celebrated Christmas tree.

Where does the tradition of the Christmas tree come from?

A Christmas tree. Photo by Malene Thyssen.
Licensed under CC BY-SA 3.0 via Wikimedia Commons – 

Most people know that in 1840 Queen Victoria’s husband, Prince Albert, brought a Christmas tree over from Germany and put it in Windsor Castle. The decorated tree, surrounded by the royal family, appeared in newspaper illustrations and from then on the tradition of the Christmas tree began in Great Britain. The Victorian tree was decorated with toys, gifts, candles, sweets and cakes hung by ribbons.

Queen Charlotte, the wife of King George III in 1800, however, introduced decorated trees to Great Britain even earlier. She decided to use a Christmas tree (a potted up yew tree) instead of a yew bough to be adorned with baubles, fruit, candles and presents. The tree was, therefore, not an unknown tradition in 1840, but became a common practice among the general public after the media publicity with Queen Victoria.  By 1860 the custom was firmly grounded in England.
The history of the Christmas tree goes back much further. The ancient Egyptians, Chinese and Hebrews used evergreen trees, wreaths and garlands in ceremony as they believed evergreens symbolised eternal life. European pagans celebrated the use of evergreens to ward off the devil, celebrate the winter solstice and provide a tree for birds during Christmas time. This tradition survived Christianity and in Germany the Yule tree was placed at the entrance to a building or in the house during the midwinter holidays.
A Christmas pyramid from approximately
1830. Picture by Klaaschwotzer,
via Wikimedia Commons.

The modern Christmas tree originated in Germany where the tree was decorated with apples to represent the Garden of Eden on December 24th (the religious feast day of Adam and Eve). It was also decorated with wafers (to symbolise the host) but later became cookies and candles, to represent Christ. The Christmas pyramid, a structure made from pieces of wood and decorated with figurines, evergreens and candles was also used in addition to the Christmas tree. It was the merging of these two structures in the 16th century that lead to the tradition of the modern Christmas tree.

It is rumoured that the religious reformer Martin Luther invented the Christmas tree. Apparently, one night in 1536 he was walking through a pine forest and was amazed by the beauty of the stars amongst the branches of the pine trees. It inspired him to set up lights on his Christmas tree to remind his children of the starry skies. The custom was widespread within German Lutheran communities by the 18th century and was a well-established tradition by the next century.

What are the most common species of Christmas tree in the UK?

The names fir and spruce are liberally applied to anything that looks vaguely like a Christmas tree. Those of us that are botanically minded are aware that the name “fir” is applied to members of the genus Abies (spruces are Picea).
I do not generally pick the common species of Christmas tree. For a while, my husband and I used to bring in a potted up Korean Fir (Abies koreana). It was small, but perfect in shape and form, and at a young age produces very pretty cones that are violet purple in colour and stand upright on the branches. However, we moved overseas and gave our tree a new home in my parent’s garden where it promptly withered and died after being contained in a pot for about 5 years!
Over the years we decided to go bigger as our decorations got more numerous after having children. We now settle on Abies fraseri (the Fraser Fir), a north American species very similar to Abies balsamea in its form and fragrance. These species are popular in North America (the firs are firm favourites) and in England the popular fir species is the Nordman Fir (Abies nordmanniana). This tree is originally from Russia and is known for its ability to retain its soft, dark green needles. Its conical shape and gaps between the branches allow optimal decoration hanging. The other popular fir in this country is the Noble Fir (Abies nobilis or Abies procera), which is glaucous green in colour with an upswept open conical shape.
Blue spruce foliage.
Photo by Nickolas Titkov from Moscow, Russian Federation

It is the Norway Spruce (Picea abies), however, that most people in England consider to be the traditional Christmas tree (it is the one I always relate with my childhood Christmases’). It has a lovely forest smell, though it loses its needles more readily than the firs. Other common spruce species include Blue Spruce (Picea pungens glauca), with its vibrant blue tinge and strong citrus scent (although it is very prickly), and the Serbian Spruce (Picea omorika), which is very popular in central Europe. It has a graceful conical shape with dark green colouring, soft needles and a pleasant fragrance.

For my family, the Fraser Fir reminds us of our time living in Canada and evokes fond memories of past Christmases’ with our children. In a few years, we will probably opt for a pot grown tree, which we can then plant out – hopefully with more success than the Korean Fir!

Fruit: the good, the bad and the ugly

Posted on by andy.winfield

By Helen Roberts



Autumn is my favourite season. I love the colours, cooling temperatures and crispness of the air in the morning. One of the things I like most, however, is harvesting autumn fruit to use in cooking, baking and jams. So far, this autumn I have picked bucketfuls of blackberries, autumn raspberries, damsons, plums, apples, pears, quince, crabapples, rosehips and sloes.
It has been a wonderful harvest and my cupboards, freezer and larder are full of these delicious fruits as cakes, jams, jellies, butters or just shoved in the freezer to be used in the depths of winter. These are all fairly common and useful autumn fruits to most of us in the UK, but as I was poking about in my garden the other day I noticed quite an unusual fruit growing.
The fruit of chocolate vine (Akebia quinata).
Photo credit: Helen Roberts.
The fruit belongs to Akebia quinata,commonly known as chocolate vine – a vigorous climber that is growing really well in my garden. I have two plants growing up a north facing wall and a west-facing wall respectively and they are more or less planted in what I can only describe as gravel. They have always been strong growers despite neglect, but they have never produced fruit.
Last winter I decided to prune it back really hard with some hand shears as it was getting unruly. I thought I may have been too severe and they may not make it, but this summer they produced a mass of flowers and early autumn produced some lovely large weird sausage shaped fruit.
The plant is native to Japan, China and Korea. The sweet but insipid fruit pulp can be eaten, while the rind of the fruit is used like a vegetable in cooking – often stuffed with minced meat and deep fried. The leaves are used as a tea infusion.
Inspired by the weird and wonderful fruit in my garden, I ventured to the Botanic Gardens for a tour with botanical horticulturist, Andy Winfield. I told Andy I wanted to see some unusual fruit and seeds.

The Garden’s weird and wonderful fruit

The first plants on the tour, which were listed at the welcome hut of current things to see, were sunflowers. The variety, ‘Giant’, produced a rather wonderful forest that rose a couple of metres above us. My sons have grown this variety but the ones in the Garden are colossal by comparison.
Cape gooseberry (Physalis peruviana) fruit is wrapped in
a papery calyx. Photo credit: Helen Roberts.
In the same bed were two species of Physalis, a genus in the nightshade family (Solanaceae). Physalis philadelphica, or the tomatillo, bears small green-purple fruit and are a staple of Mexican cuisine in dishes such as salsa verde. I tried one and it tasted a bit like a very sweet tomato – I wasn’t enamoured, but I think they are better cooked. Physalis peruviana, the Cape gooseberry, on the other hand has a wonderful sweet pineapple-like flavour. The fruit is smaller than the tomatillo, bright orange in colour, with lots of little seeds inside. Just like the tomatillo, the fruit is enclosed in an inflated papery calyx.
Sweet chestnut (Castanea sativa).
Photo credit: Helen Roberts.
Walking towards the hops in the western herb garden we walked past a fairly young Sweet Chestnut tree (Castanea sativa), which had dropped numerous spiky chestnuts, many of which had split to reveal the lovely glossy brown nuts inside. These nuts are roasted in many different countries and used to make stuffings for meat or vegetables. I have a bit of a sweet tooth so I am very fond of the use of these nuts in confections, puddings, desserts and cakes, my favourites being crème de marron and marrons glacés. Chestnuts used to be the food of the poor and were used by peasants as a staple instead of grains in parts of southwest France and parts of Italy. In France the chestnut tree is often referred to as l’arbre à pain, or the ‘bread tree’ as the chestnuts were ground into flour. The trees can grow to an impressive 20-35 metres in height with a 2 metre diameter trunk.

The cocoa tree’s tiny flowers are clustered
directly on the trunk. Photo credit: Helen Roberts.
My tour continued into the glasshouses to look at some economically important plants as well as others that are simply weird and wonderful looking. The cocoa tree, Theobroma cacao, was our first stop – after all, who could pass on chocolate? This smallish tree with large glossy green leaves lives in the Garden’s tropical glasshouse and is a native of central and South America. At first glance it’s quite unassuming, but look a bit closer and you can see the distinctive shape of the cocoa pod. I was amazed by the size of the tiny cream flowers that grow in clusters directly on the trunk – a term known as cauliflory – and that these tiny flowers can produce such a large fruit. The pod contains 20-60 seeds within a white pulp, which are the main ingredient of chocolate.
The history of cacao dates back to the early formative period (1900-900 BC) when it was considered a very important part of Mesoamerican culture. The beans constituted both a ritual beverage and a major currency system in pre-Columbian Mesoamerican civilisations.
“We had a volunteer working at the gardens who used to work for J S Fry & Sons – a chocolate manufacturer in Bristol,” revealed Andy. “He said you can make about five bars of chocolate from one pod!”

The citrus known as Buddha’s hand (Citrus medica var. digitata).
Photo credit: Helen Roberts.
The tropical glasshouse also houses a weird looking citrus called ‘Buddha’s Hand’, Citrus medica var. digitata, which is cultivated in Japan and China. It looks like a small wizened citron with fingers. The fleshy peel can be steamed and candied fresh or it can be used for its highly aromatic and fragrant zest. The fruit has been an offering in Buddhist temples for a long time.
After the glasshouses, Andy took me to the pond where there is a rather ancient looking medlar (Mespilus germanica) tree, laden with fruit. I see this tree a lot in the various gardens I visit, but I have never used the fruit for anything.
 

Fruits of the medlar tree (mespilus germanica).
Photo credit: Helen Roberts.

“The fruit needs to be ‘bletted’,” said Andy, “which is when the fruit is browned by rot after a frost or naturally in storage over time. Then it can be eaten raw or used to make desserts, jelly, medlar cheese [akin to lemon curd] and wine.”
I recall my mother making medlar jelly, but I cannot remember ever tasting it. Perhaps I will try making something of the medlars after our first frost. My tour inspired thoughts of jam making sessions with some new and exotic fruits. There are lots of weird and wonderful fruits at the Botanic Garden right now – definitely worth a visit – who knows how it will inspire you?!

The Native Bluebell: Britain’s favourite flower in trouble

Posted on by andy.winfield

by Helen Roberts


It is a beautiful spring morning in May and I am taking my children for a walk. We are venturing to some local woods on the edge of the Mendip Hills, a stone’s throw away from our house.

The woods are secreted away in a limestone gorge. The stubby cliffs of limestone are clothed in ivy and gradually open up into a steep sided valley. A tiny stream channels through the gorge; tributaries often disappearing down sink holes. We trek across a ploughed field to the gate that lets us into the wood.

As we pass through the kissing gate, there is an overwhelming smell – it’s the heady perfume of the native bluebell, Hyacinthoides non-scripta. The woods are carpeted in vibrant blue (the colour almost glows it is so vivid), dotted with ferns and intermingled with wood anemones (Anemone nemorosa), Lady’s smock (Cardamine pratensis), wild garlic (Allium ursinum), greater stitchwort (Stellaria holostea) and yellow archangel (Lamiastrum galeobdolon). It is one of my favourite places for a walk in the spring and it is made special because of the sight and smell of bluebells.

Bluebell woods in Britain are under threat

British woodland with bluebells in bloom

Bluebells blanket the ground in British woodlands
this time of year. Photo credit: Shelby Temple

Bluebell woods are an iconic part of our natural heritage and are one of the most beautiful sights to encounter in the British countryside. They were voted Britain’s favourite flower in Plantlife’s ‘CountyFlowers’ project in 2002 and we have 50% of the entire world population in our country.
Sadly, the indigenous bluebell, Hyacinthoides non-scripta, is in danger because it cross breeds with the commonly planted Spanish bluebell (Hyacinthoideshispanica) and with the resulting fertile hybrid (Hyacinthoides x massartiana). Molecular studies have shown that the Spanish bluebell and the native bluebell have a shared ancestor [1], but Hyacinthoides non-scripta has developed in isolation over the last 8,000 years, its range to the north of the Spanish bluebell [2].

Polluting bluebell genetics

The Spanish bluebell has been grown as a garden plant in Britain since 1683 [3] and it and its hybrid have now ‘gone over the garden wall’ and are encroaching on our native bluebell woods. Its leap over the ‘wall’ has most likely been facilitated by bulbs being thrown out or dumped near native woodlands. The Spanish bluebell looks a thug of a plant next to our native one – being a much bigger plant – and is reported far more vigorous. 
Hyacinthoides non-scripta
Native bluebells are low to the ground and
deep blue to violet in colour. The flower spike
distinctly nods to one side. Photo credit: Glyn Baker
[CC-BY-SA-2.0 (http://creativecommons.org/licenses/by-sa/2.0)],
via Wikimedia Commons
In its native range, the Spanish bluebell has a wider ecological tolerance to that of the native bluebell. It copes better with drier and more exposed conditions and can therefore grow in more open sites, such as roadside verges and waste ground. The Spanish bluebell is a garden favourite because it’s so much larger and can establish itself and grow quickly. Both the Spanish bluebell and its hybrid, however, have the ability to take over leading to the loss of genetic integrity of the native bluebell.
The native and bluebell hybrid are really difficult to tell apart even by expert botanists and sometimes the only way to distinguish between them is to apply DNA analysis. Many gardeners are sold the hybrid mislabeled as ‘English Bluebell’ and have planted them in good faith thinking these were the native bluebell.

The hybrids were first recorded in the wild in 1963, though they were likely there long before then as the Spanish bluebell was first recorded in the wild in 1909. The Natural History Museum gives good guidance on how to identify your bluebells with a supporting video given by botanist Fred Rumsey here.

Nation-wide bluebell surveys show extent of Spanish bluebell invasion

A survey performed by Plantlife International in 2003 found that one in six broadleaved woodlands surveyed were found to contain the hybrid or Spanish bluebell. The survey drew attention to the threat posed to our native bluebell as well as the need for more research in order to better understand species distribution, gene transfer across species and appropriate horticultural management of bluebell species.
Thankfully, it has been illegal (without a license) for anyone to collect and sell native bluebells from the wild since 1998 as they are protected under the Countryside and Wildlife Act (1981). Current legislation allows for the issuing of a special license to collect wild seed for commercial sale. These safeguards ensure that collection is done sustainably and protects wild bluebell populations.
The native bluebell is a priority species under the UK BiodiversityAction Plan (BAP). Plantlife International states that it’s vital that the horticultural industry stop the deceiving sale of the Spanish and hybrid bluebell as native bluebell. Plantlife has also worked with Flora Locale to set up an industry code of practice. Flora Locale helps people get in touch with suppliers in their area who sell seeds of local provenance. Another initiative between Landlife and the Mersey Forest produces a legitimate source of bulbs grown from seed with a long term programme running to plant them in new woodlands. Plantlife International also gives advice about making sure that gardeners check suppliers of bluebells and how to remove Spanish or hybrid bluebells from your land – read more here.
The Natural History Museum launched a bluebell survey in 2006 (of which you can take part) to look at the extent to which non-native bluebells have spread into the British countryside. Results from the last eight years show that most bluebells in urban areas are now hybrids, but fortunately there are still large areas of countryside containing our native species.
Since 2010, the survey has concentrated on comparing the flowering times of native and non-native bluebells to understand how they will each respond to climate change. By comparing recent surveys with past data, it is possible to find out whether the flowering season is changing. These data need to be collected over many years in order to tease out any real effects of climate change from the natural fluctuations inherent in any population.

Sources:

[1] Grundmann, M. et al. (2010). Phylogeny and taxonomy of the bluebell genus Hyacinthoides, Asparagaceae [Hyacinthaceae]. Taxon, 59 (1): 68-82.
[2] Natural History Museum [website] Hyacinthoides non-scripta (British bluebell). http://www.nhm.ac.uk/nature-online/species-of-the-day/biodiversity/endangered-species/hyacinthoides-non-scripta/
[3] Pilgrim, E. and N. Hutchinson. Bluebells for Britain: A report on the 2003 Bluebells for Britain survey.  Plantlife International. <http://www.plantlife.org.uk/uploads/documents/Blubells-for-Britain-report.pdf>

More sources of information on bluebells:

Preston C.D. et al. (2002). New Atlas of the British and Irish Flora: An Atlas of the Vascular Plants of Britain, Ireland, The Isle of Man and the Channel Islands. ISBN: 9780198510673. [Provides information on each taxon]

Tines T.D.. et al. (2012). The Wild Things Guide to the Changing Plants of the British Isles. ISBN: 9781905026999. [Provides information on the spread of non-native bluebells]

We’re gardenin’ in the rain

Posted on by andy.winfield

By Helen Roberts


It has been unbelievably wet since the start of 2014 with England experiencing it’s wettest January since records began over 100 years ago. The Somerset levels have suffered dreadfully and huge areas are still underwater and are likely to remain so for weeks or even months to come. From where I live, on the Mendips, I have far-reaching views over to Glastonbury Tor and the Quantocks and the area of levels in between looks like the vast inland sea it once was. In most other areas, the ground is completely saturated and in some places water is bubbling up to the surface.

Flooding in Greylake, Somerset in February, 2014. Photo
courtesy of Live-vibe on Flickr CC. 

What does waterlogging do to our gardens and what can we do to solve it?


Many plants do not like to be waterlogged because their roots need oxygen as well as water and nutrients. When roots are starved of oxygen they die and these dead roots can then act as a host for fungi such as Phytophthora, a root rot. Shrubs and fruit trees are particularly vulnerable to waterlogging as they cannot put on new roots as quickly as perennials and cannot stand long periods under water. Add freezing conditions with waterlogging and your plants may be in big trouble.
Winter flooding may not be fatal though, as many plants can experience and survive winter flooding for short periods of time. You can give your plants a helping hand if they’re waterlogged by pruning ornamentals right back so that they don’t have to protect so much above ground. You can also remove any dead or dying shoots and take cuttings as a back-up should the plant die. Smaller plants can be transplanted into pots with fresh compost, removing dead roots before transplanting.
Looking after waterlogged lawns is a different matter. If your lawn is squelchy to walk on at the moment, try to stay off it. Walking on it will only aid compaction and make matters worse. Waterlogged lawns can quickly lead to the grass dying and moss, algae, lichens and liverworts taking over. I do not have an issue with these plants in a lawn per se and I am not one to fret over weeds in a lawn either, but if you do want to make things better and improve a waterlogged lawn there are a number of options.

You can try pricking, spiking or slitting the surface of the lawn with powered tools or even a fork. This leaves holes that can be infilled with lawn top dressings or horticultural sand. It is best to get rid of surface water first, if possible, by sweeping it off with a brush into the borders. Otherwise, wait for it to drain naturally. Alternatively, convert your lawn into a water meadow!

Create a partnership with nature


Sometimes struggling against waterlogging in your garden or parts of your garden is a losing battle. It is simply better to accept the natural conditions of your garden and work with what you have. Rethink your palette of plants and cultivate those that favour wet soil. If the ground is permanently wet, consider establishing a bog garden as bog plants can be truly architectural in their habit and are excellent for attracting wildlife.

Some suitable bog species suggested by the RHS website include:
Herbaceous perennials: Bog primulas, Eupatorium maculatum Atropurpureum Group, Darmera peltata,Iris ensata ‘Rose Queen’, Iris laevigata, Ligularia ‘The Rocket’, Lobelia cardinalis, Rodgersia pinnata‘Superba’, Trollius x cultorum ‘Superbus’
Grasses: Spartina pectinata ‘Aureomarginata’, Carex elata ‘Aurea’
Ferns: Athyrium filix-femina, Matteuccia struthiopteris

A sustainable approach to managing flooding

How we manage water and excessive water in our own gardens, particularly in urban areas where there is nowhere to drain excess water, is very relevant at present considering the amount of rainfall we have had over the last couple of months.
Sustainable urban drainage systems or SuDS are approaches of managing surface waters taking into account quantity (flooding), quality (pollution) and amenity issues of water. They ultimately contribute to sustainable development and improve urban design. These systems mimic nature and manage rainfall as close as possible to where it falls aiming to slow water down before it enters watercourses. This is basically done by forming structures and landforms that can store water and allow water to soak into the ground, evaporated from surface water or lost through evapotranspiration. 

The use of SuDS is not by any means a new concept to ecologists, engineers, architects and landscape architects. It has been implemented very successfully worldwide and been effective in its way of managing water but also contributing significantly to the production of some truly innovative and outstanding design as well as creating areas of ecological value.

So how can you manage rainwater on a smaller scale in your own garden?

Nigel Dunnett, Professor of Planting Design and Vegetation Technology, and Director of the Green Roof Centre at the University of Sheffield is an expert in rain gardens and small scale rainwater management features. His research has looked at innovative approaches in planting design and landscaping that serve to store, collect and infiltrate rainwater runoff. Examples include the use of storm water or through flow planters, which are essentially raised, planted beds at the base of buildings that can take runoff water directly from roofs or adjacent areas of hardstanding.
The key to Dunnett’s research is that it can be replicated on a small scale in one’s own garden and can be just as effective in terms of its aesthetic and ecological value, particularly in urban areas.
Other approaches to managing rainwater include reducing runoff from hard surfaces, such as driveways and patios, by using permeable paving that allows water to soak directly into the ground. Roofs on sheds and garages or any external outbuildings in the garden could have green roofs installed. Furthermore, you could use Dunnett’s techniques of creating rain gardens and create a truly sustainable garden that works with nature and not against it.
Nigel Dunnett was a recent speaker with the University of Bristol Botanic Garden Friends’ Lecture series.

‘Tis the season of seed cleaning

Posted on by andy.winfield
Weeks ago, Nick suggested I come in on a rainy day to the garden as there was lots of seed cleaning going on in the potting shed. Then it didn’t rain for three weeks. Defeated by the glorious Autumn weather we’ve had, I phoned Froggie, and asked whether I could come in to learn about seed washing…yes, that’s right, I said “washing”. I’m such an amateur! However, Froggie was kind and  refrained from laughing at me and just said, “we don’t really wash the seeds unless they have a particularly fleshy covering”.
We arranged a time for me to come in and, as it happened, it was yet another glorious sunny day. While this made for a nice bicycle commute for me, it meant that the volunteer gardeners were all out in the garden so I would be having an individual, hands-on learning experience with respect to seed cleaning.

So many envelopes

As Froggie and I entered the potting shed, she took me immediately over to a bench lined with trays in which rows of envelopes were stacked up. On the outside of each envelope is written the plant’s latin name, the family name, the year the seed was collected, which collection the plant is from, the accession number and a number that corresponds with its numbered listing in the Garden’s Index Seminum. This is a catalogue of the seeds and spores that have been collected in association with the University of Bristol Botanic Garden. This catalogue goes out annually to the Friends of the Garden, other Botanic Gardens and research institutes. Requests can be made for small quantities of seed for the purposes of research, breeding, conservation and education, or by members of the Friends of the Garden (subject to certain conditions).
The Garden likes to keep three years worth of seeds, but obviously different seeds have different storage potential. Some species, such as those in the Apiaceae family, which includes celery and parsnips, are generally only viable for a year, while other seeds have been found in archaeological digs that are estimated to be thousands of years old and have remained viable (see the 2,000 year old Judean date palm as an example).
Separating the seeds of Salvia forsskaolii. 
“We’ll keep back older years from groups such as the cereals, oats and wheat, as well as beans and peas,” said Froggie, “as they will likely remain viable and it’s good to have a reserve.”
Froggie explains that with the Garden’s involvement in the Seeds of Change project, there are even more demands on their seed stores. Though schools and community groups are encouraged to collect their own seed, the Botanic Garden is sending out lots of seed to start the projects off or replenish projects where collection efforts haven’t been successful.
In the little office at the back of the potting shed there are even more trays of seeds. This is where the staff compile all the seeds that go on the Botanic Garden’s annual seed list. Now having a sense of what the end product looks like, I sense that Froggie is about to show me how much work goes into filling each of these envelopes…

Separating the seed from the chaff

Pouring the Salvia seeds into a sieve to get
rid of the chaff.
I’m shown yet more trays of envelopes – but much bigger envelopes this time – many with stems poking out the top. The gardening staff and volunteers have collected the seed heads and placed them in these envelopes ready for cleaning and this is where the work begins. Froggie picks out the first envelope, it’s Salvia forsskaolii, commonly known as Indigo woodland sage.
We sit at the table, each with a white tray nestled within a larger black tray, which I assume is to collect the seeds that catapult out beyond the borders of my white tray. Froggie doles out a few sprigs of dried plant and shows me that the best technique for this particular plant is a simple flick of the seed head to help release the seeds. I flick and my white tray is scattered in small black seeds. Easy.
With the larger unwanted bits removed, we now pour our tray contents into a sieve to clean the seeds of any smaller bits. The clean seed is then poured into a smaller envelope that is placed back into the big envelope with the remaining plant material that is yet to be cleaned. When all the plant material has been worked, Froggie will then process the seed envelope, doing and final quality control check on the seed and making sure all the information is clearly written on the envelope.  
Nigella damascena before we begin to collect the seed.
We wipe down our trays and spray an anti-static spray to ensure there is no contamination as we move on to our next species – Nigella damascena. This too requires a tapping method, though some persistent seeds need to be squeezed out. There are numerous implements on the table for crushing plant material to get at the seed, but Froggies says they try to discourage crushing as much as possible as it makes for a lot of fine chaff that is difficult to separate out later.
As we work, Froggie fields questions from the volunteer gardeners who are looking for equipment or just confirming that what they’re doing is right. As we work, Froggie relays a few stories about misguided efforts of volunteers – stories of pruning gone awry or cutting back incorrect species – she chuckles about it all and has an ‘it all grows back’ sort of attitude about it. I know Froggie no doubt has a million other things she needs to be doing, but she gives me her full attention and focus and makes me feel as though she has all the time in the world for me. She creates a calming atmosphere, which no doubt comes in very handy when coordinating the efforts of so many volunteer gardeners and teaching new skills.
What my tray looks like after I’ve removed the Nigella seeds
from the seed heads. 
There is quite a bit of fine material mixed in with the Nigella seeds and so Froggie introduces me to another technique for separating seed from chaff. She takes some newspaper and folds it in half and pours seed and fine chaff together onto the paper. Then with a motion not dissimilar from a chef tossing almonds in a skillet, she carefully tosses the seeds in the paper. The fine, lightweight chaff moves to the top of the crease in the paper, while the heavier seeds move down. She can then simply give a very gentle blow to get rid of the chaff off the top of the paper. In the end she’s left with just the clean seeds.
We start on the last one – Avena orientalis – a grass. For this seed you hold the spikelet in one hand and flick the seed out. This particular species has a lovely dark seed, so it is very clear when you’ve got it all separated. 
Froggie uses newspaper to separate the lightweight chaff
from the heavier Nigella seeds.
Not all the seed cleaning is this easy. There are dust masks as some can be particularly dusty – but the staff tend to do the really nasty seed cleaning themselves, letting volunteers do the easier ones. If this were a rainy day, there would be volunteers everywhere working on this and having a good old chat.
Looking at the stacks of envelopes, I ask Froggie when seed cleaning needs to be finished.
“We need it all complete by February at the latest,” Froggie replies. “The seed list goes out in February and people will start to put requests in. We also start sowing at the end of February, beginning of March.”

Checking the lists

Cleaned Avena orientalis seeds with the
lighter leftover spikelets in the background.

In many of my excursions to the garden, the staff have introduced me to the many lists that they keep. There is a seed sowing list, a putting the garden to bed list, and now, I have seen the seed collecting list. This is where the staff make notes against each species – for example, if a plant was too small or late to come into flower. These notes are kept year to year and so if a species is less productive in one area of the garden than another or from one year to the next, all of this information is captured.
“The list is never finished,” says Froggie. “I will just update it when something else changes.”
In years where they are unable to collect seed for a particular species, they draw upon their reserves from previous year so that it can remain on the seed list. Annuals tend to be a priority, but also shrubs. The Garden works hard to insure that there is variety on the seed list.
As a member of the Friends of the Garden myself, I now look forward to receiving the seed list next year and I will have a much better appreciation of the work that goes into collecting the seeds for each of the nearly 200 species listed.

An apple a day

Posted on by andy.winfield

by Helen Roberts

Name three things Somerset is famous for and most people will say cider, Cheddar cheese and the Glastonbury Festival. While I could certainly talk at length about cider and its versatility (particularly having enjoyed a lovely mug of mulled cider recently at bonfire night), it is where cider begins – the humble apple – that is the subject of today’s post. I live near Wells, in the heart of Somerset, and the trees in the apple orchards are positively dripping with fruit at the moment, a welcome sight for orchard growers who had a dismal season in 2012. It was National Apple Day on the 21st of October, and many places around the UK have been hosting events to celebrate England’s national fruit. Humans and the common apple have a long history together in terms of its cultivation and it is a familiar fruit throughout the world. Essentially, the richness of this sweet little fruit lies in its ordinariness.

A brief history of the apple

The (not so) humble apple.
The domestic apple (Malus domestica) is derived from both Malus sieversii (from Central Asia) and the crab apple (Malus sylvestris). The domestic apple is thought to be derived from Almaten in eastern Kazakhstan and the northern slopes of the Tien Shan Mountains. Apple taxonomy is highly complicated, and I shall save you the details, but the Malus genus is included in the Rosaceae family and has approximately 55 species, which are divided into intraspecific groups or cultivars.
Evidence of apple collecting has been found in Neolithic (11,200 years ago) and Bronze Age (around 4,500 years ago) sites throughout Europe and there is evidence for its cultivation as early as 1000 BC in Israel. Carbonized fruits dating from 6500 BC have been found at Çatal Hüyük in Anatolia and remains of both sour crab apples and a larger form, which may have been cultivated, have been found at lake dwellings of prehistoric origin in Switzerland.
It is thought that apple seeds were probably transported along the greatsilk trade routes from Central China to the Danube by travellers, either in saddlebags or in horses’ guts as early as Neolithic and Bronze Age times. The routes passed through Almaten and the northern slopes of the Tien Shan Mountains.
Improved forms of apples are thought to have developed in the FertileCrescent, which covers Israel, Lebanon, Jordan, Syria, and Iraq. Apple trees reached Palestine in about 2000 BC and from there, were taken to Egypt.
Apples were important in Ancient Greece and various writings give evidence of the propagation of apple trees. Homer in the Odyssey, written between 900 and 800 BC, describes a large orchard of both apples and pears. It is the Romans that are credited with developing apple cultivation and storage. They recognized the importance and profitability of orchards and brought apples, and hence orchards, to Western Europe. Many Roman writers mentioned various cultivars of apples in their writings.
During medieval and pre-industrial times monasteries became major centres for apple production, particularly for cider production. King Henry VIII imported many different cultivars during his reign from 1509 to 1547, including pippins from France. In the mid 16th century, Dutch refugees escaping from religious persecution moved to Kent and Surrey to set up market gardens to supply London, and planted orchards for this purpose. During the 16th century and early 17th century grafting was further developed in Europe with specific rootstocks being imported from France and then propagated in English nurseries. European settlers, introduced apple culture to North and South America, South Africa, Australia and New Zealand. The first documented apple orchard in the USA was planted near Boston in 1625.

Cider making

The word cider is derived from the latin word sicera which means ‘strong drink’. The first recording of cider making is from Norfolk in 1205, but it was common in many different areas of England, particularly the western counties of Somerset, Devon, Worcester and Hereford. Apples suitable for cider have a sweet juice and an acid pulp. The names given to cider apple varieties are lovely in themselves, varieties known as “bitter sweets” and “bitter sharps”, such as  Slack-me-Girdle, Foxwhelp, Lambrook pippin, Chisel Jersey, Porter’s Perfection and Royal Somerset.
Cider making takes part in late Autumn and the traditional method was to crush the apples between heavy stone wheels driven by horses. In the West Country the resulting pulp was then spread onto straw or wooden racks and cloths and a large sandwich or ‘cheese’ was made by laying one rack on top of the other. Set into a wooden press, it was squeezed repeatedly and the juice collected. I remember watching this method of cider production at a local farm as a child in Central Somerset. Today cider has made a come back and there are many smaller scale producers cropping up in areas of the West Country.
Bristol University has a long history of research into cider production at Long Ashton. The research station was originally set up to facilitate the development and improvement of West Country cider and formed the National Institute of Fruit and Cider (NIFC). Scientists identified the best apple varieties, growing conditions, and production methods for growers and cider-makers; many cultivars, such as Ashton Brown Jersey, orginate from Long Ashton.   

Weird and wonderful facts

Apples are very much entwined in our culture and history. Many popular apple-based phrases, such as “the apple of my eye”, “an apple a day keeps the doctor away”, “rotten apple”, “rotten to the core” and “upset the apple cart”, are embedded within our culture. Other words also have apples at their core (groan);  costermonger – a street seller of fruit – comes from the Costard apple. “Costard” means ribbed and gave rise to “coster”, while “monger” means seller.
Erika Janik, author of Apple: AGlobal History, said the apple is “Enmeshed in the folklore and history of nations around the globe, apples have been associated with love, beauty, luck, health, comfort, pleasure, wisdom, temptation, sensuality and fertility – all this in addition to good eating and drinking.”

Apples at the Botanic Garden

If you managed to get to the Bee and PollinationFestival at the Botanic Garden, you will have seen a small cider press in action. You may have also seen a potted orchard on display near the pond, featuring a number of varieties of apple, including Bramley, Golden Delicious, Lord Derby, Ashmead’s Kernel, Discovery, James Grieve, Spartan, Fiesta and Greensleeves. It was yet another example of how pollinators are critical to our food security – pollination of our orchards and the production of the (not so) humble apple.

The benefits of flowering early

Posted on by andy.winfield

Bristol was a swirl of snowflakes and blossoms earlier this week. Monday on my walk the cutting wind was relentless. Yet, despite my frozen nose and numb fingertips, I stopped to admire the many splashes of colour along my route – a street lined with blossom-laden plum trees, front gardens lined with daffodils, heather and crocuses, splashes of primulas and even some snow drops in the local woods. As my teeth chattered despite my thick down coat, I did marvel at these early spring bloomers that have clearly found it to their advantage to flower despite cold temperatures, relatively short days, and a paucity of pollinators. So, what exactly arethe advantages of being the first blossoms of spring?
A robin and crocuses, both soaking up some sunshine
on Thursday at the Botanic Garden.

Early woodland blossoms have access to more light

The first and perhaps most obvious advantage is that these early blossoms appear before the deciduous trees come into leaf, which gives them more access to light. Many of these early blossoms are naturally woodland flowers and so as soon as conditions become tolerable, these flowers put all of their energy into producing foliage and flowers before the forest canopy has formed. If successfully pollinated, the plant will produce a seed for dispersal. Then, as the forest floor becomes shaded by the trees above, the flower and foliage die back and any unused nutrients are returned into the roots or bulb. There will be no sign of these plants above ground for the rest of the year.
Though this may sound very much like a ‘get-up-and-go’ approach to flowering, the timing of when each species, and indeed each plant, flowers is incredibly complex and scientists have yet to figure out all the intricacies. It is affected by physical factors, such as soil nutrients, water, sunlight, day length and temperature, but it is also affected by biological factors, such as abundance of pollinators, herbivorous predators, seed dispersers and competition from other plants.  All of these factors may ultimately affect the reproductive success of the plant; flower too early and there may not be sufficient to set seed, but flower too late and the bird species that normally disperse the seed may have already migrated to over-wintering grounds.

There is less competition for pollinators

Though there are fewer pollinators about in early spring, there are also fewer blossoms to compete for their attentions. Insects that emerge in early spring or that forage throughout the winter, such as some bumblebee species, do not have a plethora of blossoms to choose from, so this increases the likelihood that the flowers that are out will get a visit.

There is more time for seed maturation

For some early season blossoms, such as fruit trees, there is an enormous investment in seed production, which takes time. The benefit in the end, of course, is a rather extravagant and often delicious means of dispersing seed great distances.

Early blossoms favour out-crossing  (Munguía-Rosas et al., 2011)

Fewer blossoms in early spring also mean that pollinators will travel greater distances between flowers. As a result, a flower may receive pollen from a more distant flower, which may be less similar genetically. It’s the floral equivalent of “bringing in new blood”, also known as out-crossing.  Perhaps the genetic material carried in that pollen encodes some increased resistance to frost or disease…or perhaps not. Most importantly, it is adding diversity to the population, which is the foundation for adaptation.
The crocuses in my front garden are in full bloom.

The evolution of early bloomers

There are not only differences in the time that plants flower between species, but also between populations of the same species and between plants of the same population. For example, the crocuses at the front of my garden, which have been exposed to more direct sunlight, are much further along than those in my back garden, which are shaded by a cedar hedge. This is a clear example of differences in the resources available in these two different growing environments.
However, consider a woodland covered with bluebells, what drives those first few bluebells to burst out before the others? It might be slight differences in their growing environments, but it is also in part a result of their genetic makeup. A sort of bluebell “aptitude” if you will that predisposes them to go to flower quickly – two separate bluebells, under the same growing conditions, may still flower at different times. Of course, it is therefore inevitable that those bluebells that are first to bloom will be pollinated by others that are in blossom, giving rise to new generations of early bloomers.
It might also be that environmental conditions are such that early bloomers are for some reason more successful in reproducing, perhaps because pollinators favour early bloomers (Munguia-Rosas et al., 2011). This will eventually drive the flowering time of entire populations earlier each season and over time this will become fixed within the genetic makeup of that population, in as few as three generations for some species (Galloway and Burgess, 2012).

Temperate plants tend to be more flexible with their flowering times

In temperate climates, there are much bigger differences in variables such as frost, temperature and day length across the landscape, between the seasons and between years. As a result, flowering plants in these regions exhibit tremendous variability in their flowering time – it is an adaptive flexibility that enables them to take advantage of the best growing conditions possible regardless of when they might happen (within reason of course).

If you’re going to be a risk-taker, be sure and have a plan B

Of course, many of these early spring blossoms have what could be considered a back-up plan. Snowdrops, crocuses, and daffodils are all capable of both sexual and asexual reproduction. So, if there is a prolonged heavy frost after these flowers have emerged or they are not successfully pollinated for any other reason during the season, then the bulbs will still form new small bulbs that are genetically identical to the parental bulbs. However, it is sexual production that brings genetic diversity to a population and this is what will allow a population to adapt to changing environmental conditions and resist disease.
There is a lovely clip herefrom the BBC’s Private Life of Plantson their website showing the progression of early blossoms as a British woodland bursts to life in the spring.
Well, I hope you are getting the opportunity to enjoy these early spring blossoms! Also, be sure to come out to the Botanic Garden over the Easter weekend to enjoy the Easter Sculpture Exhibition – amazing art, refreshments, and garden tours sounds like an ideal way to spend a weekend to me, I’m definitely going to be there!
Here are the references used above:
Galloway LF and Burgess KS. 2012. Artificial selection on flowering time: influence on reproductive phenology across natural light environments. Journal of Ecology 100: 852-861. http://www.cfbiodiv.org/userfiles/1111.pdf

Munguía-Rosas MA, Ollerton J, Parra-Tabla V, De-Nova JA. 2011. Meta-analysis of phenotypic selection on flowering phenology suggests that early flowering plants are favoured. Ecology Letters 14 (5):511-521.