Category: trees

The pretty peony – a flower of culture

Posted on by andy.winfield

By Helen Roberts

The peony has undeniably beautiful flowers, from the perfect spherical bud giving a hint of the petal colour underneath to the rapid unfurling of immense blooms. Even the foliage is attractive, particularly towards the end of the season when they readily take on autumnal tints.

I admire them in gardens that are not my own for I have never grown peonies, the tree nor the herbaceous species. The flowers, although staggeringly large and of sublime colours and subtle scents, are too short lived for my own small garden. After all peonies need space. However, I am looking forward to the development of a new peony garden in the University of Bristol Botanic Garden. It will form part of a new ‘Culture’ display, which is being implemented this year with the help of the Chinese Garden co-ordinator, Tony Harrison, who is a traditional Chinese herbalist.

Tree peony. Image credit: RHS

Peonies are native to Asia, Southern Europe and North America and are contained within the Paeoniaceae family. There are 4 different types, the tree peony, herbaceous peony, the hybrids and the intersectional peonies, which are crosses of tree and herbaceous peonies. Tony explains the different species of tree peonies [1]:

‘When they first arrived, the Chinese tree peony was thought to be a single species which was named Paeonia suffructicosa, but research showed P. suffructicosa to be a hybrid which has been derived from at least three main species which have been interbred over several thousand years to produce the wide range of cultivars from different regions of China. These original source species were then separated into three separate wild species as P. ostii, P.jishanensis and P. yunanensis.’

A number of species will be cultivated in the new peony display at the Botanic Garden. These will include ones from different regions of China including the wild species of P. ostii, P. jishanensis and P. yunanensis as well as P. delavayi, P. rockii and P. suffructicosa, and several herbaceous species.

A long history of medicinal use

Peony tubers have been used for medicinal purposes for centuries. The bark of the roots is used to treat congestion, blood disorders and worms [2]. Tony explains the importance of peonies in Chinese medicine:

‘Peonies were being used in medicine long before they were cultivated for ornamental purposes. It is considered that peonies have been used medicinally dating back about 2,000 years. The root bark of the tree peony is used to cool and move the blood, whereas the herbaceous peony is used to tonify the blood. The Chinese name for peony is mudan (牧丹) and the characters can be translated to mean the colour “red” but also “medicine” and “healing”. The bark is separated from the remainder of the root, chopped, dried and used in combination with other substances.’

The plant is also revered for its attractiveness. The flower colours range from yellow, cream, red, pink; all the way to lavender and near black [3]. Some have a unique, almost peppery and spicy, scent. I am fond of the smell, it is not cloying or overpowering like some flower scents. The choice of peony hybrids and cultivated varieties is vast, there are so many to choose from. The herbaceous peonies are more commonly grown in Europe and North America and because of this familiarity with the herbaceous form, tree peonies are not as popular. I prefer the tree peonies as they offer interesting foliage and architectural form.

The tree peony has been grown for its flowers in China since the 6th and 7th centuries during the Sui (581-618 AD) and Tang dynasties (618-906 AD) when it appeared in the imperial palaces. It is rumoured to be one of the first flowers to be cultivated purely for its ornamental purposes from the ancient city of Luòyáng and the seat of the Sung dynasty (960-1279 AD), hence it is often called luòyànghuā or flower from Luòyáng [2]. The enthusiasm during the Sung dynasty for peonies is comparable to the tulip mania that gripped Holland in the 17th century and immense sums where paid for highly prized peonies. In Luòyáng many peony exhibitions and shows are still held there annually. Peonies in China are normally cultivated by planting in terraces or raised beds and protected from the harsh summer sun by mat awnings [2].

The symbolism of the peony

Along with many other flowers grown in China, the peony is shrouded in layers of symbolism. Among the tree peonies (Peonia suffruticosa), the male vermilion flower is known as the ‘King of Flowers’ (花王 hūawang) and represents both royalty and aristocracy [2]. The tree peony was originally grown by royalty, the aristocracy and eventually, over time, throughout China. In the imperial palaces, it was often displayed in opulent reception halls, being used as a table plant in large vases. The ink and deep red forms as well as a variety with a yellow edge on the petals, known as the ‘Golden border peony’ were highly valued [4]. The peony is also called fùguìhūa (富貴花), the flower (hūa) of wealth (fù) and rank (guì) symbolising wealth, social status and honour [2]. Despite being associated with the yang principle (male) of masculinity and brightness it also represents female beauty and reproduction, especially erotic lushness [5].

The flowers of the four seasons – the tree peony is spring.
Image: Jimmie on Flickr [CC By 2.0]

The tree peony is one of four flowers which symbolise the seasons; tree peony –  the spring (and March); the lotus – summer; the chrysanthemum – autumn; and the plum – winter.

The herbaceous peonies are termed the ‘Prime Minister of All Flowers’ and are also highly prized.
As well as using the plant form itself, peonies have long been depicted in Chinese art forms (literary and visual) for centuries and they form one of the main motifs in silk tapestries, paintings, lacquerware and clothing. They are often displayed alongside peacock, pheasant, fowl, phoenix and lion to represent splendour, status and nobility [2].

Such is the importance of peonies in Chinese culture that numerous stories and poems have been written and told. There is the wonderful fable of ‘The Fabulous Peony’, where the wicked and vain Empress Wu Zetian ordered all flowers in the Imperial garden to bloom overnight in winter and those that did not would be punished. The senior member of the Imperial garden, the Male Vermillion Peony refused to obey, whilst the other flowers in the garden submitted and duly produced blooms to please Empress Wu.

In her fury at being disobeyed, the peony was banished from the Imperial Palace and anyone growing it would be put to death. To save the peony from destruction the royal gardener, Pei Fu sent roots of the peony to a friend in Luoyang, a place considered lacking in culture and hence not likely a place to arouse suspicion. And here the peony flourished, the peony gardens at Luoyang remaining a secret until the death of the Empress Wu when it emerged out of hiding [6].

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:

[1] Harrison, T. Varieties of Peony. Journal Archive. The Register of Chinese Herbal Medicine.
[2] Williams, C.A.S., 2006. Chinese Symbolism and Art Motifs: A Comprehensive Handbook on Symbolism in Chinese Art Through the Ages. Tuttle Publishing.
[3] Fearnley-Whittingstall, J., 1999. Peonies. Harry N. Abrams.
[4] Li, H.L., 2012. Chinese flower arrangement. Courier Corporation.
[5] Welch, P.B., 2013. Chinese art: A guide to motifs and visual imagery. Tuttle Publishing.
[6] Chew, K., 2008. The Magical Dumplings and Other Chinese Fables. iUniverse.

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!

Forests may be more vulnerable to pests and disease in the future

Posted on by andy.winfield
As I sit in my home office watching the autumn rains and winds strip the last remaining colourful leaves off the trees outside, I find myself in awe of the tree. There’s a primary school across the street from my house and there are several huge beautiful chestnuts in its grounds where I watched the children shelter from the sun on hot days. There’s also the spindliest little apple tree that one could imagine, which despite its size produced at least a dozen enormous apples this year!
Trees affect every aspect of our lives – they provide food, timber, pulp and fibre, but beyond this they have important ecosystem functions in the natural landscape. Trees help to regulate our climate, they store and sequester carbon (about 30% of global CO2 emissions are absorbed by forests), they store water helping to prevent floods, they purify water and they provide habitat.
However, widespread pests and diseases have taken their toll on natural forests over the past century with outbreaks seemingly becoming more frequent and widespread in recent years. There has been considerable focus on the devastating effects of these outbreaks on trees with large economic value – orchards and timber plantations for example – but what are the consequences of the widespread death of our forests in terms of ecosystem services?
Oak in its autumn colours.
A review published recently in the journal Science considers this exact issue. UK researchers from the Universities of St. Andrews, Cambridge and Oxford reviewed the consequences of tree pests and diseases on ecosystem services around the globe.  The authors concluded that our current approaches to pest and disease management do not take into account the ecosystem services or the beneficiaries of these services provided by forests and that new approaches are needed, particularly as the likelihood of pest and disease outbreaks increases as a result of global climate change and globalisation.

Who’s attacking our forests?

Trees are attacked by any number of pests and diseases, including bacteria, viruses, invertebrates, water molds and fungi. The effects of these pathogens may be compounded as well; trees that have been defoliated by insects may be more vulnerable to disease.
Millions of years of co-evolution have generally allowed trees to build up natural defenses to the pathogens they encounter in their native environments.  However, the introduction of species or the movement of species outside their historical ranges has opened up a whole new world of pathogens that have been the cause of the most devastating attacks on our global forests in the last 200 years.
The American chestnut (Castanea dentata) was devastated by chestnut blight – a fungus accidentally introduced to eastern North American forests around 1900. In the early 20thcentury, over a quarter of the trees across approximately 200 million acres of eastern hardwood forests were American chestnuts, but by 1993 its frequency had declined to 0.5%. Today the tree is effectively extinct as very few mature trees are producing nuts.
Dutch elm disease – another fungal pathogen, which is transmitted by bark beetles – is familiar both in North America and Europe as it has eliminated mature elms (Ulmus spp.) from much of the landscape. Now there is concern that ash (Fraxinus excelsior) could suffer the same fate due to another fungal pathogen (Chalara fraxinea), which has been killing trees in Poland since the 1990s. Scientists are monitoring its spread to the rest of Europe.
The devastation wreaked on a Canadian forest by the
mountain pine beetle. Credit: D. Huber, Simon Fraser University
Public Affairs and Media Relations (Flickr CC).
As a Canadian I would be remiss if I didn’t also mention the devastating effects of the mountain pine beetle (Dendroctonus ponderosae). It has already killed several million hectares of pine species in Canada and the US and they expect over 37 million hectares of forest to be affected in British Columbia alone before 2020.
Of course, with globalisation and the widespread movement of plants and plant products around the world, the frequency and spread of pests and disease is only likely to increase. Climate change will also improve conditions for pests and disease as milder conditions in some areas may let some pathogens increase their natural range, or may permit pest populations to explode in numbers.

Attack of the Frankenfungus


When pathogens move around the globe they are not only introduced to new hosts and plant prey, they can also escape the natural predators and diseases that keep their populations under control.
This global movement also exposes pathogens to new genes that can make them even more virulent. For example, when the fungus that causes Dutch elm disease, Ophiostoma novo-ulmi, spread across the northern hemisphere, it hybridised with a native fungus species (O. ulmi) and acquired some new genes that decreased the elm’s ability to resist infection.   

What does the loss of dominant tree species mean for our forests?

Widespread loss of a dominant tree species can have devastating effects far beyond any economic value they may have had. A wide range of ecosystem services will initially be harmed, such as retention and purification of water, wildlife habitat and carbon storage. Large stands of dead trees also become fuel for wildfires, which are far less specific about their victims and further alter the ecosystem.
However, inevitably the lost trees are replaced by new species and as this natural succession occurs some of the ecosystem services will be restored – carbon storage and water purification, for example. Unfortunately, other ecosystem services may never be restored. New tree species will create different habitats altering the biodiversity. 
Some ecosystems are particularly vulnerable as they are dominated by a species that plays a critical role in maintaining the structure of that ecological community – known as a keystone species. Boreal forest (or taiga) is an excellent example of this. The conifers that dominate the northern latitudes of boreal regions are adapted to short growing seasons, recurring disturbance from storms, fire and floods, and growing in peatlands. Loss of any species in these regions would have a significant impact on the ecosystem structure.

Climate change packs a one-two punch for forests

Not only does climate change have the potential to increase the numbers and range of pests and disease, it can also make forests more susceptible to these infestations. Though the future is uncertain, predicted increases in extreme weather events – droughts, floods, cyclones, and extreme temperature fluctuations – are likely to put our forests under severe stress, increasing their vulnerability. 
Of course, some pests may also be hindered by climate change. For instance, species that rely on an insulating blanket of snow to overwinter may be more vulnerable if snow cover is reduced in a milder climate scenario.

What is the future of our forests?

Nobody knows the answer to this question. However, the UK authors of the Science paper bring to light the need to do more fundamental research in understanding how pathogens affect natural forest communities. To date, most research has focussed on economically important species, yet the ecological role of forests and the ecosystem services they provide have considerable value also.
The long life span of trees has been a barrier to understanding some aspects of the infection and spread of some pathogens; the time it takes for some trees to reach a reproductive stage could outlive the careers of some scientists. However, new methods in molecular biology are overcoming these barriers these days. Understanding the process behind these pathogens will help in the prediction of their spread as well as how they may respond to climate change.
The authors also call for better management approaches that identify different classes of threat, which are defined by (i) the type of disease-causing agent (e.g. fungus, bacteria, insect), (ii) how it moves (e.g. wind, water, animal, wood imports) and (iii) the type of ecosystem service threatened (e.g. keystone species, timber value).
Management practices can also help build resilience in our forests. For example, practices that help preserve the genetic diversity of species and avoid monoculture will provide the genetic foundation that will help species resist disease. Steps to mitigate climate change may help reduce the abiotic stress on forests and reduce the expansion of pest populations.

Though there remain many unknowns and the future is uncertain, the critical role forests play globally is clear. So, if you are able, get out into a local wood or forest today and appreciate it. Those trees are cleaning the air we breathe and the water we drink. They grew that apple you brought along for a snack! They’re doing a lot as they stand there, so appreciate it…dare I even say…hug a tree?!  Who knows, you might start a trend?!
The original paper is: Boyd IL, Freer-Smith PH, Gilligan CA, Godfray HCJ. (2013) The consequence of tree pests and disease for ecosystem services. Science, 342 (6160): doi 10.1126/science.1235773
The AAAS press release associated with the paper can be found here.