Category: conservation

African keyhole gardens open the door for school gardening

Posted on by andy.winfield

By Helen Roberts

A keyhole garden in Rwanda. 
Photo courtesy of Send a Cow.

Back in June, my son’s primary school, located in a small village on the edge of the Mendip Hills, built something called a keyhole garden in their grounds. Having no idea what a keyhole garden was, I thought I would offer up my services as a parent volunteer for the garden day.

The idea of keyhole gardens originated in Africa out of necessity. They enable families to produce food on dry, exposed and rocky soils – essentially land that is infertile. The gardens are shaped like a keyhole and act like an organic recycling tank using food and garden waste as fuel to grow vegetables.

The garden day at my son’s school was organised and facilitated by a charity organisation called Send a Cow. This charity helps families and communities in Africa by providing farmers with the skills and tools they need to farm using sustainable and organic methods. Farmers on the programme are given the gift of livestock, seeds and other assets and every farmer makes a pledge to pass on the gift of training, seeds and livestock to another family in need. 

The facilitators from Send a Cow held a morning workshop with the children to discuss building the keyhole garden and the materials needed. Two sixth form pupils from another local school were there to help with the session and contributed enormously to the discussion, engaging with their younger peers and getting them interested in the activities. These two students are hoping to run Send a Cow African Garden Day workshops themselves. 

A tip tap hand washer in Uganda.
Photo courtesy of Send a Cow.

Some of the children also learned about tip tap hand washers. These are a simple water conserving/hygiene device used in African countries aimed at improving hygiene and preventing the spread of diseases. Send a Cow shows families how to make them.

Laying the foundation

I joined the children in the afternoon to help build the garden. My pre-schooler was eager to muck in too as he is an avid gardener and had already donned gloves with trowel in hand in eager anticipation of the job ahead! 

The keyhole garden was to be located along a major walk way, on a patch of grass that would be visible to the children walking to their various classes. This would enable them to see what was happening with the garden on a day-to-day basis and judge whether the garden needed weeding or watering. A group of children were assigned the task of building the stone base around the patch of bare soil that had had the turf removed the previous week. This turf was recycled back into the garden via the school compost bins. 

The foundation of the garden can be made from
whatever resources are available. This garden is in Lesotho.
Photo courtesy of Send a Cow.

The prepared ground was a typical keyhole shape, with a 1.4 metre radius circle and an entrance triangle starting from the circle centre to the edge of the circle. The entrance is north facing to allow more room for sun-loving plants. The children worked hard moving and placing stones in a double layer for the outer wall- a little taster of the backbreaking work done by people who build dry stone walls. 

For all key hole gardens, the simplicity of the design means materials can be sourced locally. In Africa, this includes many creative construction materials, such as plastic bottles filled with sand, instead of stones or bricks for the main structure of the key-hole garden base. We used Mendip limestone. 

After the stonework, a steady flow of soil mixed with manure was wheel-barrowed across the school grounds and excitedly transferred by spade into the garden. The children had previously made the composting basket, which is central to the keyhole garden, out of runner bean canes (or sticks), string and chicken wire. This was placed in the centre whilst the soil was piled around it. Composting material was then placed in the compost basket, along with straw.

Planting it up

The finished garden at the primary school.

Planting up the garden was the most exciting part for the children. The volunteers had a line of seedlings lined up for the students to plant carefully. Typically, the vegetables commonly grown in African keyhole gardens include spinach, amaranth, gourds, Tithonia (eg tree marigold), chillies, sweetcorn and climbing beans. Plants with deep roots that require lots of feeding are planted near the centre of the garden. Herbs are added near the rock walls to help bind the soil and compost. 

In the Mendip school garden, tomatoes, lettuce, cabbages, peas, sunflowers, cornflowers, nasturtium and calendula were planted out. Flowers were added to the vegetables to add colour and other benefits. Nasturtiums are useful companion plants because black aphids, black fly and cabbage white butterflies cannot resist them and feed on them rather than the crops. 

“It was a fantastic day and the children really enjoyed it and still talk about it avidly,” said Mrs Savage, the school reception teacher. 

The African Garden Day informed the children about positive ways people in Africa are feeding themselves sustainably, but it’s also a long-term teaching tool and resource to get children interested in plants. 

“All the summer sunshine has done wonders for the African Garden created by the children last term,” said Mrs Williams, the school’s Head Teacher over the summer. “It is looking amazing and we are very proud of our achievement!”

There are plans afoot to develop a second garden, but more in keeping with Somerset traditions using weaved willow to form the base wall and compost bin.

African Garden Days is one of many programmes run by Send a Cow. It is the UK’s largest global learning project with approximately 30,000 children taking part. African Garden Days offers primary schools the chance to experience a fantastic hands-on day, combining classroom sessions with an outdoor challenge to create a global kitchen garden within the school grounds. It is aimed at Key stage 2 and 3 children, but also involves the whole school in an assembly and class session. The cost of running the garden day goes directly back to Send a Cow.

Green roofs part II: lofty havens for wildlife

Posted on by andy.winfield

By Helen Roberts

The green roof industry has been aided over the past few years by an unlikely character. The black redstart (Phoenicurus ochruros), a robin-sized bird of strange habits, has not only helped draw attention to the green roof industry, it has advanced development of green roof design.
The black redstart is unusual in its call, looks and ecological preferences. Its song starts with a hurried warble followed by a sound similar to that of scrunching of a bag of marbles. Males have a fiery red tail and the species has a propensity to hang out in industrial places.
Within the urban environment, brownfield sites can be rich in biodiversity and can be lost when they are developed. The story of the black redstart is inextricably linked to that of humans and urban centres. Black redstart population numbers have fluctuated in the urban environment due to human activity, and this is where the story of the black redstart has impacted the green roof industry in a positive way.
During and after the Second World War the black redstart population soared because bombsites provided a habitat that closely replicated their preferred habitat found on the scree slopes of the Alps. With redevelopment of areas of London, however, populations declined. Other cities also saw a drop in numbers as a result of development.

Laban Dance Centre in London.
Credit: rucativava,
CC-BY-SA-2.0, via Wikimedia Commons

Deptford Creek in London, an area that was earmarked for development, was important for its populations of black redstarts. The developers were pushed by wildlife groups to provide suitable habitat for the birds through the implementation of green roofs. This truly innovative solution to mitigate the decline in black restart populations led to the development of green roofs designed specifically for black redstarts. The rubbleroof of the Laban Dance Centre in London, installed in 2000, was the first of these in the UK. Rubble roofs, such as the Laban Dance Centre’s, replicate the features of a brownfield site and often incorporate materials from the original site. They have a mix of aggregate materials such as crushed brick and concrete, stones and boulders. The Laban Dance Centre roof also incorporates features such as logs and sand boxes in order to study nesting bees. It has been monitored since 2002 and a number of rare invertebrates have been recordedusing the habitat.
Numerous studies have shown that green roofs help support several Red Data book invertebrates and UK Biodiversity Action Plan species such as the brown-banded carder bee (Bombus humilis) and the nationally scarce Bombardier beetle (Brachinus crepitans) and that these green roof conditions can be replicated at other sites.

The right plants for the right roof

Incorporating the right plant species in to the design of a green roof is important for achieving biodiversity objectives. Simple sedum matting has been shown to have little ecological benefit for invertebrates, though they do provide sources of food for foraging bees in summer.
A truly exemplar green roof that is rich in plant species is the Moos Filtration Plant in Zurich, which cleans all the water for the inhabitants of Zurich. Yet, this green roof came about by chance as there was no original intention to create a green roof as part of the building design. When the filtration plant was built, the multiple roofs were covered in exposed waterproofing which subsequently caused the water below the roof deck to become polluted with bacteria due to high temperatures during the first summer. In order to moderate the temperature of the roofs, a 5cm sand and gravel layer was laid down followed by a layer 15-20cm deep of local meadow topsoil. This soil was teeming with flower and grass seed and it became a flourishing 30,000m2 meadow. Today these expansive roofs provide habitat for 175 species of plants, many of which are rare and endangered at a local and national level, including 14 species of orchid. The roofs now have special protection under Swiss nature conservation laws. 

Due to the pressures of habitat loss through urbanisation, it is becoming increasingly important for biodiversity to be retained. If land is lost at the ground level through building, then green roofs help provide stepping stones above for wildlife and can provide valuable habitat for flora and fauna that would not ever be found on a conventional roof. 

Raising the ‘green’ roof

Posted on by andy.winfield

By Helen Roberts


We currently have a real shortage of housing in the UK and the estate agency Savills has estimated that there will be a shortfall of 160,000 homes in the next five years unless local authorities act. With this in mind, I started thinking of the building industry and how sustain­­able building design has become increasingly important over the last few decades. Not only does the industry consider the sustainability of the materials themselves, but designs aim to reduce consumption of non-renewable resources and minimize waste during and after the life of the building, while creating a healthy and comfortable environment for the occupants.

Within the field of sustainable building design is the subject of green roofs. This is an area of design that holds great interest to me, as I am a landscape architect with previous training in plant sciences. Green roofs play a pivotal role in urban environments by reducing rainwater runoff, reducing energy consumption for heating and cooling, heat island mitigation, creating valuable wildlife habitats and also making an aesthetically pleasant landscape for people to escape from the urban environment. 

What is a green roof?

Green roof on Chicago City Hall. Photo credit: TonyTheTiger
[CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0)
via Wikimedia Commons

A green roof is a platform or roof on which vegetation is grown or wildlife habitats are created. The basic elements include a waterproofing membrane covered with a growing medium and vegetation. The design, ecology and aesthetics of a green roof can vary considerably, however, and can be adapted specifically to suit a particular location or design brief. Plants in containers on a roof top are not considered to be a true green roof.
The term green roof, however, can also be used to describe roofs that incorporate green technology, such as solar thermal collectors or photovoltaic (solar) panels.

The history of green roofs

Green roofs are not a new concept. Dwellings of the Neolithic period, such as the Neolithic village of Skara Brae in Orkney, are thought to have had turf roofs. The Hanging Gardens of Babylon, one of the wonders of the Ancient World, were extravagant green roof gardens, thought to be irrigated by about 35,000 litres of water brought in through aqueducts and canals.

The houses at Skara Brae, Orkney were thought to have
had turf roofs. Photo credit: Antony Slegg
[CC-BY-SA-2.0 (http://creativecommons.org/licenses/by-sa/2.0)],
via Wikimedia Commons

Turf or sod roofs were common centuries ago in Scandinavia and can still be seen in places like the Faroe Islands. I visited Lund, Sweden recently and saw beautiful turf roofed farmhouses in the museum of cultural history. The turf helped keep dwellings cool in the summer and warm in the winter. However, these structures would most likely have leaked and also would have had the inconvenience of burrowing wildlife!
Modern green roofs didn’t develop until the 1970s in Germany, when legislation was passed to encourage the introduction of green roofs. Unlike the historical turf roofs, modern green roof designs include drainage and root protection measures, as well as lightweight growing media.
The UK is somewhat behind continental Europe in terms of using government policy to implement green roof technology. But things are changing and there has been an increase in the use of green roof technology over the past decade. In fact, Bristol’s development policy (Bristol Development Framework Core Strategy; adopted in June 2011) encourages the incorporation of green roofs as a way of enhancing the biodiversity value of new building developments and views green roofs as an essential asset of the strategic green infrastructure network.Bristol  

Green roofs can be extensive, intensive or semi-intensive

Green roofs vary in ‘intensity’ in terms of the depth of substrate used and the level of maintenance needed, which affects the type of vegetation that can then be grown. A typical green roof will have, on top of the roof itself, a layer of waterproofing, a root barrier, protection/moisture retention matting, a drainage layer, a filter sheet, the growing substrate and then the plants. Green technology, such as solar panels, may also be incorporated into the design of the vegetated roof.
Green roofs are classified as extensive, intensive or semi-intensive in nature. Extensive green roofs are less than 100 mm deep and are relatively low maintenance. Their shallow depth means they are lighter but that they can support fewer vegetation types. This means they generally have lower biodiversity value and limited water holding capacity. Most people will be familiar with sedum matting as a common form of extensive green roof.

Construction layers of a green roof.
Photo credit: thingermejig (flickr.com)
[CC-BY-SA-2.0 (http://creativecommons.org/licenses/by-sa/2.0)],
via Wikimedia Commons

Semi intensive green roofs have substrate depths of about 100 mm to 200 mm, require moderate maintenance, can support a greater range of plant species and have the ability for rainwater attenuation.
Intensive green roofs have deeper substrates (over 200 mm) and therefore require more substantial structural support. The deep substrate can sustain more elaborate plantings, including many different tree and shrub species, which offers a more garden-like space for users. Intensive green roofs require more maintenance and complex drainage and irrigation systems, but can offer rainwater attenuation and a greater degree of species biodiversity.
The aim of the green roof will ultimately influence its design. If, for example, the aim is simply to have an insulating effect on the building, a low-maintenance extensive green roof with low-lying vegetation would probably be sufficient. If, however, the aim is to attract and enhance wildlife, an intensive design is likely required to support a diversity of plant species that can provide a variety of structure and microhabitats. I will discuss biodiversity and wildlife green roofs in more detail in my next blog post.


The benefits of green roofs:

Green roofs help improve the urban environment in many ways, from creating a natural space for office workers to enjoy to helping mitigate the urban heat island effect. Here are some of the benefits of green roofs:

Creating a biodiverse space and a relaxing place

Green roofs can increase biodiversity in urban areas where ground level space has been developed and valuable green corridors lost. Sky-high gardens can be important stepping stones for wildlife and can create habitat and forage for a variety of species, which wouldn’t exist with conventional roofs.
These places can also provide a haven for people to visit or to just view and offer a respite from a hard urban setting. 

Green roofs slow down runoff and help reduce flooding

There is a requirement now in the UK (under the Flood and Water Management Act 2010) that new developments mitigate storm water runoff and include appropriate water management systems. An established green roof can significantly reduce the peak flow rates and total volume of water runoff. Water is stored by the plants and substrate and is released back slowly into the atmosphere by evapotranspiration and evaporation. The plants also help filter out pollutants in the rainfall.
Many features of Sustainable Urban Drainage Systems (SUDS), such as permeable surfaces and swales, are not easily incorporated into a hard urban and so green roofs are considered a good solution to reducing storm water runoff. Interestingly, it has been found that in the summer 70-80% of rainfall can be retained in a green roof and in winter 10-35% (due to differences in evapotranspiration in summer and winter). 

The cool down effect of green roofs

Urban areas that are hotter than nearby rural areas are described as heat islands. The additional heat means more energy is used in summer for cooling (air conditioning and refrigeration), there are more incidents of heat-related illness and mortality and there are implications for air and water quality. Green roofs help improve local air quality and cool the urban environment by reflecting more of the sun’s rays compared with conventional roofs. The plants shade and insulate the underlying roof and have a cooling effect as water is released through evapotranspiration and evaporation – the building equivalent of sweating.

Green roofs reduce energy consumption

The thermal insulation properties of green roofs reduce the need for air conditioning in summer and heating in winter, decreasing associated emissions and dependence on non-renewable resources. 

Green roof allotments

There is increasing interest in the use of green roofs for food production and this ties in closely with the provision of amenity space. There is limited green space that can be used at ground level for food production in urban areas, so the logical step is to go up!. Roof-top allotments reduce food transportation and help increase the supply where the demand exists. For the individual household, it can help reduce food costs and provide many benefits associated with growing your own food. For a community, rooftop gardens can become a centre for social cohesion.
Though there are examples of agri-roofs, mainly in Asia, the use of roofs for food production is relatively unexplored and will provide ‘food for thought’ in the design of future green roofs.

Raise the roof on green roofs

With their many benefits, green roofs are likely to become a vital component of building designs in the future. New developments are imminent in the face of a housing shortage and green roofs offer an opportunity to improve the urban landscape, providing habitat for essential species, such as pollinators, and potentially helping respond to challenges with food security. Green space that is lost on the ground needs to be created up above with the transformation of featureless barren roofs into beautiful diverse green places. 

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]

Plants that endure

Posted on by andy.winfield

by Helen Roberts

Whether perched upon a windblown cliff or nestled in a small crack deep within a canyon, some plants seem to overcome all odds of survival. These survivors, which are frequently rare, quite often grow in remote inhospitable environments, show true resilience and perseverance and are highly adapted to their specific habitats. You just have to admire them for their sheer tenacity.
However, some of these ‘bulldog’ plants aren’t the hardy-looking brutes one might expect of such survivors; sometimes they are delicate and very beautiful. Discoveries of plants such as these are occurring regularly with over 2,000 new plant species being found worldwide each year. Many are found in far flung areas of the globe, as well as on our very own doorstep here in Bristol.

A Malaysian beauty

The newly described Ridleyandra chuana with a
rare two flowers. Photo credit: L.S.L. Chua
A rare and endangered endemic plant found in the biologically diverse Pennisular Malaysia has recently been described. The beautiful plant is called Ridleyandra chuana and is only found in two small mountainous areas of forest.
The plant can be simply described as a perennial herb that is somewhat woody with a rosette of dark hairy leaves at its base. It has a long slender unbranched stem with very delicate and beautiful cone like flowers, which are white with dark maroon purple stripes.
This herb grows in very challenging habitats, such as moss covered granite rock emdedded in soil or moss covered granite boulders in extreme damp and shade on steep slopes.
The maroon/purple cone-like flower of
R. chuana. Photo credit: L.S.L. Chua.
The plant was initially discovered back in 1932 at Fraser’s Hill, Pahang, but only recently have enough data been collected to formally describe the plant. It is named after botanist and conservationist Lillian Swee Lian Chua who discovered another population whilst carrying out a biological inventory of summit flora on Gunung Ulu Kali, Pahang. Because of its limited numbers (only 130 individual plants are known to exist) it has been classed as Endangered under the IUCN criteria. Of the two locations of where it is found, one location is threatened.
“The population at Fraser’s Hill falls within a Totally Protected Area and consists of about 30 plants that grow in an undisturbed site away from tourist trails and is too remote to be affected by development,” said Dr Ruth Kiew, author of the recent study describing this exquisite plant. “The other population consists of less than 100 plants at Gunung Ulu Kali, which is on private land in a hill resort that is severely threatened by road widening and associated landslips, by changes in microclimate due to edge effect as the forest becomes more and more fragmented and that is in danger of encroachment from future development. The chances of this latter population surviving is very slim. On the other hand, the rediscovery of the Fraser’s Hill population after a hundred years illustrates the resilience of species to survive if the habitat remains undisturbed.”

A beauty closer to home

Such rare and endangered plants that cling to life in the most inhospitable places are also found not too far from Bristol Botanic Gardens and are now being displayed at the Gardens as part of their ‘ex-situ’ conservation collections. The Avon Gorge, a Carboniferous limestone gorge cut out by the River Avon provides a sheltered microclimate of sun-baked niches for a wide variety of endemic species within ancient scrub and grassland communities. Many of these species are threatened by scrub invasion, introduced species and engineering works. Of these rare species, there are two endemic whitebeams, Sorbus bristoliensis and Sorbus wilmottiana that literally cling to life in the Gorge. 

They are being grown at the botanic gardens and also a number of newly discovered and described endemic whitebeams are currently being cultivated to add to the existing whitebeam collection. Wilmott’s Whitebeam (Sorbus wilmottiana) is listed by the charity Plantlife as one of our 10 most threatened woodland plants in the UK, which is why ex-situ populations are so important in helping to understand species and aid in the long term management and future development of the AvonGorge. The study and protection of rare plants is beneficial in the long run not only to the individual species, but also the plant communities to which they belong.