A walk through the mendips

By Helen Roberts

A few weeks ago our family, had a great day out walking on the Mendip Hills. We set off in autumn sunshine, through pretty deciduous woodland, to an Iron Age hill fort called Dolebury Warren – an upland area of calcareous grassland. Having lived on the edge of the Mendips during my childhood, I am always keen to show my children where I used to explore as a youngster.
Part of Cheddar Gorge, Somerset, England, seen from a
light aircraft. Photo by Adrian Pingstone (1975).
The Mendips are a range of mainly carboniferous limestone hills comprised of at least four convex fold structures formed between 363 and 325 million years ago, during the end of the Carboniferous Period. Weathering of the limestone has resulted in features including gorges, dry valleys, screes and swallets (sink-holes) and incorporates the famous Cheddar Gorge and Burrington Combe, each with extensive cave systems. The area also has interesting landscape characteristics like limestone pavements and other karst structures.
The geology of the Mendips makes for interesting ecological communities and consists of large areas of open calcareous grassland with many rare flowering plants. For instance, Dolebury Warren owned by the National Trust and managed by Avon Wildlife Trust, sits within the Mendip Hills Area of Outstanding Natural Beauty and is a Site of Special Scientific Interest due to its important limestone flower communities. These flower communities attract up to 70% of all British butterfly species. Dolebury Warren has a gradation of communities from species rich calcareous grassland, through acid grassland to limestone heathland, with large areas of mixed scrub.
Cheddar Pink (Dianthus gratianopolitanus).
Photo by Paul Harvey, via Wikimedia Commons
The charity Plantlife has identified the Mendips as an Important Plant Area (IPA), which is an area of landscape that has very high botanical importance. Some plant species found on the Mendips are found nowhere else. Due to factors such as over grazing, poor land management, scrub encroachment and agricultural intensification, these plants are declining in numbers and some are threatened with extinction. The University of Bristol Botanic Gardenhas a local flora and rare native plant collection, which includes a sub-collection from the Mendip Hills, Limestone Cliffs and Coastal Islands. The collection was developed to help grow and interpret some of the rare and threatened plant species found in these habitats. The collection represents an important habitat and phytogeographic display and is helping meet the objectives of the ‘Global Strategy forPlant Conservation.

Rare plants of the Mendips 


One of the Mendip plants in the Botanic Garden’s collection is the Cheddar Pink (Dianthus gratianopolitanus). This is a very pretty scented pink flower that grows in a few places on the Mendips but mostly at the original site of Cheddar Gorge. This plant was originally discovered about 300 years ago and is considered the pride of Somerset and was voted the County Flower. It grows best in rock crevices, high on the limestone crags of the Gorge, and can be seen in June and July using binoculars to search patches of colour visible on the cliffs, just above the road.
Also growing at the Gardens is the interestingly named Starved Sedge (Carex depauperata). This is an exceptionally endangered plant that is only found in one local area – in the woods and on a hedge bank near the small town of Axbridge. This is one of only two sites in the whole of the UK. Fifteen years ago, Starved Sedge had declined to such an extent that the
re was only one plant in the whole of Britain. As appearances go, it’s not much to look at. It’s a tussocky plant with trailing leaves and gigantic seeds and can easily be mistaken for some common woodland grasses. A reintroduction programme has improved the status of this plant by using cuttings and seed collecting to re-establish it at other sites in the UK.
The University Botanic Garden are also helping to preserve another plant at high risk of extinction and classed as nationally rare, known as Somerset Hair-grass (Koeleria vallesiana). Again, this is a fairly innocuous grass restricted to the Mendip Hills with very slow spreading habit. The Bristol Botanic Garden’s specimens were collected from Brean Down, which is the most westerly part of the Mendip Hills, as well as the interesting tiny islands of Steep Holm and Flat Holm.
Brean Down is an outstanding example of calcareous grassland and supports endemic plant communities that provide for many important insect communities. Other important plant species growing at Brean Down and now growing at Bristol Botanic Gardens include the White Rockrose (Helianthemum appenninum). This is an attractive white flowered perennial sub shrub, which frequently grows on southern slopes. White Rockrose, Somerset Hair-grass and Dwarf Sedge (Carex humilis) are all particularly at risk due to scrub colonization. This highlights the importance of grazing to maintain grassland habitats. The National Trust introduced grazing by long horned White Park Cattle and British WhiteCattle (feral goats are already on Brean Down) to help keep the grass short and scrub species controlled. 
The rarity of the plants found on the Mendip Hills highlights how important collections, such as those held at the University Botanic Garden, are for ensuring the survival of plants teetering on the brink of extinction. Equivalent to a botanical savings account, these collections help ensure that if plant species are lost, they can be reintroduced back into the wild.

Botanic gardens: places of research, education and beauty

By Nicola Temple

There are an estimated 3,400 botanic gardens around the world, many of which are associated with universities or other research institutions. This association with research institutions can give the impression that these gardens, Bristol’s own Botanic Garden included, are primarily research oriented and not particularly appealing to the public – nothing could be further from the truth.

In the last two years that I’ve been blogging for the Botanic Garden, I have taken myself to Kew Royal Botanic Gardens, Tresco Abbey Gardens in the Isles of Scilly, El Charco del Ingenio Botanical Garden in Mexico and the University of Alberta’s Devonian Botanic Garden. I’ve been keen to see how they differ from my local Botanic Garden that I’ve come to love. These gardens have been different in their sizes and plant collections and clearly differ in their annual budgets, but they have all been united in their commitment to educate and they have all been beautiful places to spend a day (or two).

The history of botanic gardens

One of the many spectacular species of orchid on display
at Kew Royal Botanic Gardens. Photo credit: Nicola Temple.

Botanic gardens seem to first make an appearance in the 16th century. They were set up largely as medicinal gardens where research and experimentation could be carried out on medicinal plants. They were often associated with medical schools and universities of the time.

In the 17th and 18th centuries, the focus of research changed as global exploration started to bring back new exotic species of plants. Some of these plants were medicinal in nature and were of interest for that reason. Some, such as spices, were of interest because of their economic value. Some were simply of interest due to their exotic beauty and many of the wealthiest families wanted specimens for their own collections. In the 18th century glasshouses and heated conservatories were built in some of the botanic gardens in order to keep some of the species alive that were being brought back from tropical habitats.

A corridor through the Agapanthus at
Tresco Abbey Gardens. The species was
introduced to the Isles of Scilly by the
proprietor of the gardens in 1856.
Photo credit: Nicola Temple.

The research focus of botanic gardens has continued to evolve to meet the needs of society. Today conservation, climate change and sustainability are the greatest challenges we face and as a result, many botanic gardens around the world have active research programs in these areas.  The decades, and in some cases centuries, of information collected by these gardens is proving incredibly valuable in terms of how the climate is changing and how some species are responding.

Botanic gardens play a critical role in conservation

In 2010, the Conference of the Parties to the Convention on Biological Diversity adopted an updated Global Strategy for Plant Conservation (GSPC). The University of Bristol Botanic Garden, along with botanic gardens around the world support this global strategy in every aspect of the work that they do.

The strategy recognises that without plants, life on this planet would cease to exist. The aim, therefore, is to halt the continuing loss of plant diversity. The five main objectives of the GSPC are:

  • Plant diversity is well understood, documented and recognised.
  • Plant diversity is urgently and effectively conserved.
  • Plant diversity is used in a sustainable and equitable manner.
  • Education and awareness about plant diversity, its role in sustainable livelihoods and importance to all life on Earth is promoted.
  • The capacities and public engagement necessary to implement the strategy have been developed.

The El Charco del Ingenio Botanical Garden in San Miguel
d’Allende, Mexico had many parts that were less formal than
other botanic gardens. Photo credit: Shelby Temple.

The University of Bristol’s Botanic Garden developed the Local Flora and Rare Native Plant Collection in response to the GSPC. In the eight habitat themed displays associated with this collection – Carboniferous Limestone grassland, woodland and cliff face (found locally in the Avon Gorge & Durdham Downs, Mendip Hills and North Somerset cliffs and coastal islands), Coastal Communities, Deciduous Woodland, Aquatic and marginal areas, hedgerows and seasonally flooded sedge peat meadow associated with the Somerset Levels  – are many of the rare and threatened native plants to these regions. The Garden is therefore a global repository for this plant material in both these living collections as well as its seed banks. Over the coming months, Helen and I will blog about each of the Garden’s collections in more detail, so stay tuned!

A place for learning

Cactus in flower at the El Charco del Ingenio Botanical Garden.
Photo credit: Shelby Temple.

The plant collections at the Garden are used extensively by the University of Bristol for undergraduate teaching as well as in graduate student projects. Beyond this, however, it is a place to learn horticulture, art, photography, garden design, and numerous skills from willow weaving to wreath making.

Formal courses and training through the Royal Horticultural Society are also held at the University Botanic Garden – it’s an ideal setting.
< br />The Garden also offers tours – whether it’s a special interest group, school group or a group of friends wanting to join one of the summer evening tours. Having joined on a school group tour in the past, I know the volunteers are very good at tailoring the tours to draw together information the children have been learning in class with the collections on display.

A place to be inspired

A pollinator drinking nectar from milkweed (Asclepias syriaca)
flowers at the University of Alberta’s Devonian Botanic Garden
in Canada. Photo credit: Nicola Temple.

The collections, knowledge and expertise held at the Botanic Garden puts it in an ideal position to raise public awareness of the plants on display, our interdependency on plants more generally and critical issues facing many of these species, including changes as a result of global warming, habitat loss and invasive species. These are common threads in all of the communications put out by the garden.

More than this though, the Bristol Botanic Garden aims to foster an interest in plants and inspire people through its work. We can all feel somewhat paralysed by the plethora of environmental gloom and doom stories sometimes. Sometimes inspiration and awe about a species can spur people into action more easily than anger and frustration. The Garden’s annual Bee and Pollination Festival is an excellent example of this. Pollinators are having a tough go of it and a National Urban Pollinators Strategy is under development in the UK as I write this to try and improve the situation for this critical group of animals. All the important information is at the Festival, but overall this is a celebratory event – an opportunity to learn and get excited about how amazing pollinators are and how we are so deeply connected to them in so many aspects of our life.

A sunflower display at the Devonian Botanic Garden, Canada
was very popular with the butterflies. Photo credit: Shelby Temple.

The Garden can also be a quieter source of inspiration. I have now spent many hours sitting with camera in hand trying to get perfect flower shots or just simply watching bees move from flower to flower. Sometimes inspiration can be found in these quieter moments, surrounded by beauty, in a garden in a city.

'Tis the season of seed cleaning

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 institutesRequests 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 mill
ion 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.

Bringing the Levels to the Garden

If you’ve been to the Botanic Garden recently, you may have noticed an area by the pond that has been sectioned off with some ropes. This is the future home of the Somerset Levels and Moors display at the University of Bristol Botanic Garden.  It is one of the mini-habitats of areas that are found here in the West Country that the Garden is replicating as part of its display of rare and threatened plants.
The Somerset Levels run from the foot of the Mendip Hills through to the first rising of the Quantock Hills and occupy an area of about 150,000 acres. The Levels are an interesting habitat, which has formed as a consequence of some rather unique geological features as well as hundreds of years of human modification; they support a rich diversity of species and as a result are of national and international importance.

I had an opportunity to speak with both Andy Windfield, a botanical horticulturist at the Garden, and Nick Wray, the Curator, about the Levels display that’s being constructed and there is an incredible amount of thought and work that goes into it. It’s not simply a matter of taking some of the local species and plunking them down in the garden, Nick and the Garden staff are taking great care to replicate some of the natural processes, such as the seasonal rise and fall of water levels, that make the Somerset Levels such a unique habitat.  

What makes the Levels unique?

The Somerset Levels are a sedge-peat moor, which is very distinct from a sphagnum moss bog that you normally associate with upland areas in the UK or low-lying areas where there is high rainfall and little drainage. Whilst there are some sphagnum mosses on the Levels, it’s mainly sedges and grasses that grow there and this produces a different structure of peat.
Below the peat is an impermeable layer of clay that used to be the bed of a shallow sea. In fact, until the early part of the Middle Ages, large parts of the Levels were still part of an inland sea.  However, local people began to drain the area, creating dykes and ditches to lower the water level.
The Levels are still a catchment for the surrounding hills, which are comprised of primarily carboniferous limestone. This is very hard limestone and it’s hard to weather, making the groundwater running into the Somerset Levels alkaline. This is a unique situation because peat bogs are normally associated with very acidic water, yet the Levels are a sedge peat where the groundwater can be alkaline.

So, how do you replicate all this in the Botanic Garden?

First, Andy takes me out to the pond and we are standing near the rock garden – an area a child visiting the Garden once called ‘wiggly water’ and the name has stuck with all the staff here.  He explains that in 2005, when the Garden moved to this location, one of the first things they did was mark out this main pool.
“Nick started explaining what this was going to be,” explained Andy. “The main pool was constructed with the Levels display already in mind, with this side of the pond 5cm lower than the other edges. So, when the water overflows in the pond it runs down into this display area.”
The Somerset Levels display, with the large pond in the
background, has to settle before planting can begin.
 At the base of the display, they’ve put in a liner with a depth of about 30cm to simulate the impermeable clay bed. This replicates one of the key features of the Somerset Levels – the seasonal rise and fall of the water level.  In the su

mmer this display area will be allowed to dry out, but the liner below will create a reservoir below.

On top of the liner, they’ve put in truckloads of waste sedge peat (a bi-product from a former industry in Somerset). “It took staff and volunteers lots of time to move it in,” says Andy. “We’re now letting this sink and we’ll likely need to add more peat on top before it’s ready to be planted out.”
The rock garden around the wiggly water is comprised of carboniferous limestone and is planted with rare and threatened native plants of the Mendip Hills. It is not a mere coincidence that the Levels display sits adjacent. Nick explains, “Just as in nature the Mendip Hills are next to the Somerset Levels, here at the Botanic Garden the Mendip Hills are next to the Somerset Levels.”

Planting out the Levels

Many of the plants that the Garden will replicate in this area are grasses and sedges and small herbs. There are some shrubby species also and Nick points out a bog myrtle by the pond that was collected for the Garden in the 1970s from Shapwick. It has an incredible smell and not surprising as it comes from the same family as cloves, allspice and eucalyptus (Myrtaceae). Bog myrtle creeps slowly through the peaty soils and creates dense thickets in these peaty soils, so this will be one of the plants included in the display.
Nick also hopes to have a small area of some carnivorous plants because the round-leaved sundew (Drosera rotundifolia) grows in the Somerset Levels, as does the common bladderwort (Utricularia vulgaris). There will also be some ferns such as the royal fern (Osmunda regalis), which is a fantastic foliage plant that grows at the edges of the ditches in the Somerset Levels,
Some of the plants will be sown directly into the peat area once it has settled and been topped up, while others will be sown in little pots or plugs, grown on and then planted out. All seed and plantlet collection is being done with the permission of Natural England and Andy and Nick will be doing the collections themselves.
“One of the exciting plants we’ll be getting in here is a population of marsh orchids,” says Nick. “We already have those marsh orchids growing in our nursery and they’ve been raised from seed from an original collection back in the 1970s of southern marsh orchids. So we want a large population of deep pink and purple orchids.”
Once mature, the main flowering interest in the display will be late June and early July after which it will go to seed and then be cut in August to tidy it up. Then it will be allowed to be wet and grow slowly through the winter months.
Planted in the ordinary soil around the peat area, there will be species of willows, which are common to the area, including the almond willow (Salix triandra), the goat willow (Salix caprea) and, if there’s room, the common osier (Salix viminalis)> These will be coppiced so they don’t get too big.

The sweet track

The sweet track is a very ancient pathway that runs across the Somerset Levels – built in the early Bronze Age.  It consisted of posts of timber pushed into the soft peaty earth above the water with horizontal boards
of split timber fixed to them. It created a causeway about 3-4 ft above the water that enabled people to walk easily regardless of the water level.
The timbers, which were embedded into the peat, which is anaerobic, didn’t rot and so the nearly 4,000 year old relics were discovered in the 1970s and at the time were considered the oldest timber trackway in Northern Europe. Nick has contemplated trying to incorporate the sweet track into the Levels display in the Garden as well.
“I would like to find out more about what the timber species were,” said Nick, “and maybe have those species growing in our display, perhaps with a sculptural representation of the sweet track.”
I look forward to seeing the display progress over the next year as the staff and volunteers bring the Somerset Levels to life here in the Botanic Garden.