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Monday, 22 December 2014

Branching out on your choice of Christmas tree

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!



Wednesday, 17 December 2014

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.

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.

Wednesday, 10 December 2014

African keyhole gardens open the door for school gardening

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.

Monday, 17 November 2014

Green roofs part II: lofty havens for wildlife

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 recorded using 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. 

Monday, 10 November 2014

Botanists disperse some 'big data'

Recently, Botanists at Trinity College Dublin launched a database with information that documents significant ‘life events’ for nearly 600 plant species across the globe. The database is the result of contributions from individuals working across five different continents, who compiled information on plant life histories for a near 50-year span, and is an example of big data.

What is ‘big data’?
Black pine (Pinus nigra), one of the species whose life
history data is part of the database, is seen against a
stunning backdrop of New Zealand. Credit: Yvonne Buckley.

In academic circles, the buzz-term across all disciplines seems to be ‘big data’, and it means exactly what it sounds like – a whole lot of information. More formally, of course, big data refers to data sets that are so large and complex that traditional methods of processing the information contained within them simply aren't adequate. Big data draw upon many sources of information and represent a body of work that far exceeds what a single researcher, or indeed an entire research group, could gather in their careers.

While there are many challenges of working with big data – storing it, analysing, visualising it and ensuring its integrity to name a few – the benefits of working with such large data sets may make overcoming these challenges worthwhile. Repositories of such vast amounts of information can not only help foster collaborations, but they can be used to answer questions surrounding some of the most complex and pressing issues society currently faces, including climate change, food security, and mass species extinctions.

Of course, what is considered to be big data today will not be big data tomorrow as our management systems and computing capacity improve. This is the inevitable path of technological advancement; the Human Genome Project took over ten years (1990-2003) to sequence the human genome and now it can be done in a day for a fraction of the cost.

The importance of sharing knowledge
Plantago lanceolata at Howth Head, Dublin, Ireland - one of
the near 600 plant species that researchers have gathered
extensive life history data on. Credit: Anna Csergo.

The researchers at Trinity have made their database, called COMPADRE, freely available in the hope that other scientists access the information to advance their research. The size of the database means it can be used to help answer an infinite number of questions – such as how plant communities may respond to climate change or physiological processes that might provide insights into our own aging and health.

“Making the database freely available is our 21st Century revamp of the similarly inspired investments in living plant collections that were made to botanic gardens through the centuries;” said Yvonne Buckley, Professor of Zoology at Trinity’s School of Natural Sciences, “these were also set up to bring economic, medicinal and agricultural advantages of plants to people all over the world. Our database is moving this gift into the digital age of ‘Big Data’.”

The approach of free knowledge sharing is becoming more common and is a critical step toward resolving some of our biggest challenges. The University of Bristol’s Cereal Genomics Group has made the wheat genome along with hundreds of thousands of molecular markers freely available through their searchable database CerealsDB. These data can be used in wheat breeding programmes to develop new varieties of wheat that are more resistant to disease or droughts or produce higher yields.


Our best chance of overcoming some of the global challenges of the 21st Century is to work together. Sharing knowledge through databases, such as COMPADRE and CerealsDB, will ensure every scientific contribution counts towards this united effort.

Friday, 31 October 2014

Beans and bacteria – a complex story of communication

The symbiotic relationship between legumes and soil bacteria has been known for well over a century. The intimate details of this relationship, however, are only recently being revealed. It is a very active area of research as understanding this symbiotic relationship could lead to strategies that help reduce the environmental impacts of food production. 

Rhizobia nodules on the roots of cowpea
(Vigna unguiculata). By Stdout
[GFDL (http://www.gnu.org/copyleft/fdl.html),
via Wikimedia Commons.
Special soil bacteria – known as rhizobia – reside within the nodules of legumes, such as peas, lentils, beans, alfalfa and clover, which are found along the roots of these plants. The bacteria take nitrogen from the air and convert it into ammonia, which the plant is able to use – a process known as nitrogen “fixing”.

This allows legumes to grow well in nitrogen-poor soils. This nitrogen is taken up in the plant material, which can then be worked back into the soil as a natural fertiliser for subsequent crops.
While this all might sound very straight forward – there are details about this relationship that remain unclear. How do the bacteria get into the nodules? Are there signals that the plant uses to stimulate the bacteria to produce nitrogen?

An answer to a century-old debate

In 2011, researchers from the John Innes Centre in Norwich answered the mystery of how nitrogen-fixing bacteria crossed the cell walls into the nodules of legumes. 

It had been a century-old debate as to whether bacteria produced the enzymes to break down the cell walls or whether the plant did. The researchers showed that it was the plant which supplied the enzymes to break down its cell walls in order to give the bacteria access.

How legumes communicate with their symbiotic bacteria

In 2010, Stanford researchers discovered the gene in plants that triggered the chemical signal required for the bacteria to fix nitrogen. They found that the rhizobia bacteria would just sit around in the legume nodules if the plant failed to produce the protein that’s required to spur the bacteria into nitrogen fixing mode. This was only part of the communication story.

It is energetically costly for the plant to produce and maintain the root nodules in which the bacteria live; usually the benefit of having a supply of nitrogen outweighs this cost. If there is sufficient useable nitrogen in the soil, however, the plant is able to reduce the number of nodules on its roots.
Communication between the shoots of the plant and the roots of the plant help regulate the number of nodules. The leaves transmit a signal to the roots to either develop more or get rid of rood nodules, depending on circumstances. The roots communicate back up to the leaves using molecules known as peptides.

Research published recently has now discovered that the plant shoots use plant hormones, known as cytokinins, which travel down the phloem into the roots to help regulate nodule development.

The environmental benefits of understanding legumes

Understanding the symbiotic relationship between legumes and soil bacteria is not simply a matter of scientific curiosity. The ability for legumes to produce natural nitrogen fertilisers is a trait that US researchers would like to potentially transfer to non-legume crops as a way of reducing the environmental impact of agriculture.

Manufacturing nitrogen fertilisers for non-legumes is extremely resource intensive. It has been estimated that to produce 68 kg (150 lbs) of nitrogen fertiliser – enough for one acre of corn – would be the equivalent of driving a car 1,046 km (650 miles).

Beyond that, nitrogen fertilisers release the powerful greenhouse gas, nitrous oxide, after they’ve been applied. Excess fertilisers also runoff agricultural land into rivers and lakes and eventually out into the ocean. This influx of nitrogen can provoke algal blooms and create oxygen deplete dead zones.

Therefore, there is great incentive to fully understand this relationship legumes have with soil bacteria. The environmental impact of agriculture could be significantly reduced by utilising legumes with their natural nitrogen fertiliser more by using them in more marginal land and using traditional breeding programs to select for drought resistance or temperature tolerance. In some countries, genetic engineering might even be used to introduce nitrogen-fixing abilities into non-legume species. Genetic modification, however, can be an inflammatory issue with considerable debate as to its pros and cons, particularly with respect to its use in food products.

Tuesday, 28 October 2014

Fruit: the good, the bad and the ugly

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?!

Friday, 24 October 2014

Raising the 'green' roof

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. 

Friday, 27 June 2014

Children take a 'walk through time' at the Bristol Botanic Garden

It’s 1 pm, the sun is shining and the volunteer guides are starting to gather near the welcome lodge in anticipation of 60 Year 4 children arriving at the Botanic Garden for a tour. It’s my son’s school, Horfield CEVC Primary School, and so I've decided to come along for the tour and get a glimpse into how the Garden is viewed through the eyes of eight and nine year olds.

Anne is one of the volunteer guides at the garden and she and I get chatting while we await the children’s arrival. She was a teacher for 40 years – teaching at GCSE and A levels. She laughs as she tells me she was a bit nervous she would find touring younger children challenging when she started giving these school tours at the Garden. She soon found, however, that though it was different from teaching upper level students, it was also just good fun.
Volunteer guide Tony gives a talk to Year 4 students
from Horfield CEVC Primary School prior to their tour.

“I’m not responsible for making sure they learn the curriculum, I’m here to entertain them with interesting stories about the plants we have here in the garden – to get them excited and inspired by what they see,” Anne says from a shady bench.

The guides have come prepared; they know the Horfield children have been learning about Egypt and different habitat types. As well as discussing the logistics of touring sixty children around the garden in small groups, they check in with each other about plants that might be important to point out that will link to the topics and themes they've been learning in the classroom.

Then the coach arrives.

A tour through the glasshouses

Before the children break into small groups to go around the garden, volunteer guide Tony gives a very brief talk about what plants need to survive. The children enthusiastically put up their hands in response to Tony’s question of what plants need to grow. Horfield Primary is lucky enough to have a garden and most of the children will have grown plants in the classroom at some stage (my son brought a runner bean home from school a few weeks back that's doing splendidly). So, although photosynthesis hasn't been taught by Year 4, there are other opportunities where the children are learning the basic needs and processes of plant growth.

Students have a look in the pitcher plants in the sub-tropical
zone of the glasshouses.
Baking sun and a tight schedule keeps the introductory talk brief and I follow Anne’s small group down into the glasshouses. She points out the Deadly Nightshade along the way and talks about the large black poisonous berries – a good wow factor for the kids right off the start!

In the sub-tropical zone, the children talk about the challenges of plants growing in a rainforest beneath a heavily shaded canopy and some of the adaptations they've made to get alternate sources of food. They have a look into the pitcher plants to see whether any wayward insects have fallen into the plant’s pitcher-shaped trap. As Anne walks by the lichen, she talks about how lightning changes the nitrogen in the air into a form that’s easier for plants to use – lichens need a continual supply of nitrogen to survive. Lightning helps feed plants? This has the children’s attention.
Having a look at the giant lily pads in the pond in the
tropical zone of the glasshouses.

In the tropical zone the giant lily pads (Victoria) impress the children immediately. Then Anne points out the papyrus that’s growing at the corner of the pond and the children quickly make the link between this plant and the papyrus paper that they've been learning about in their Egyptian studies. As I switch between the different groups I hear one of the other guides tell a story from Egyptian Mythology about how the Scorpion-godess, Selkis, protects the child Horus by hiding him in a papyrus thicket.

The lotus plants (Nelumbo nucifera) are also linked to Egypt as there is a Nymphaea lotus that grows in the Nile. Anne encourages the children to splash some of the pond water onto the leaves of the lotus plant and I watch as two girls are astonished at how the leaves repel the water.
Water beads off the leaf of the lotus plant.

Some of the other highlights in the tropical zone were the cocoa plant, vanilla and cotton. The Madagascar periwinkle (Catharanthus) is also pointed out for its utility in treating leukaemia.

As the children stand beside the cacti in the glasshouses, they are told that some of these plants will go 10 years without ever experiencing rainfall – longer than these children have been alive. Anne and the other guides talk about all the adaptations these plants have made to go for long periods without water.
Students are given an opportunity to experience what
happens to Mimosa plants when you touch their leaves.

Time travel through the evolutionary dell

I leave the heat of the glasshouses to join Tony’s group as they begin their walk through the evolutionary dell. Tony is telling the children about horsetails (no friend of the gardener) and pointing out the nodes of the plants. He tells them that 350 million years ago this little snippet of a plant would have been the size of a tree! The kids crane their necks up imagining and as we walk toward the tree ferns one of the girls says “It feels like time travelling!”

Tony takes the children on a walk through time in
the evolutionary dell.
Indeed it is like time travelling in the dell. In the 100 m span of the dell, we travel 200 million years from the horsetails (350 mya) to the first flowering plants (150 mya), such as the magnolia that’s on the left as you leave the dell. Surrounded by ferns, moss, horsetails, Wollemia and other conifers, the guides tell the children about how plants reproduced before the evolution of flowers and pollinators.

It’s never long enough

Somehow an hour seemed to fly by and before long the guides were rushing through the last few displays before sending the children off on their coach. As I had the opportunity to hop between the different groups I got the great sense that each group would have left the garden with a different experience as each guide has their own style and favourite stories associated with the garden. It’s never possible to see everything, but hopefully that means some of the children will encourage their parents and guardians to bring them back for another visit!
Tony holds up a horsetail and talks about plant nodes.

Linking to the curriculum

Mrs Amy Parkin, one of the Year 4 teachers at Horfield Primary, was kind enough to speak with me the next day after the tour about how tours such as this link with the classroom curriculum. This is the first time Horfield Primary has done the tour at the Botanic Garden and it was prompted by Curator Nick Wray giving a talk earlier this year to the Key Stage 2 children.

“We had two weeks where we talked about prehistoric Bristol, dinosaurs and fossils,” said Mrs Parkin. “Each class did a science trail with various outside activities and we also had speakers come in to talk to the children. Nick spoke about what plants would have been around 160 million years ago and he brought in some different species to show the children.”

As well as learning about Egypt, the Year 4 children have also covered the topic of habitats under their science curriculum and there are also cross-curricular links with their geography topic of water.

“The tour at the Botanic Garden helped extend the children’s knowledge on habitats,” said Mrs Parkin. “We focused on animals in different habitats in the classroom and in the tour we saw how plants adapt to different habitats as well.”

This tour will also give the Year 4 students a taste of what lies ahead as they will have plants as a topic in Year 5.

Talking with the students after the tour

After the tour I had a chance to speak with Megan and Henry about what they thought of the Botanic Garden. Megan said “I really liked the giant lily pads, especially since a small child could sit on one!”, while Henry really liked the giant lemon that was in the glasshouse.

When I asked Megan and Henry what the most interesting thing they learned was, Megan said she couldn't believe that some plants can live for 10 years without water. Henry, on the other hand, learned something new about pollination, “There are lots of different bugs that pollinate plants – blowflies and beetles – and birds too!”

The Botanic Garden will run about 15 school tours during the months of June and July, with the help of their dedicated volunteer guides. These tours are in keeping with the Garden’s mission to promote education and awareness as well as to encourage and foster interest in plants within the Bristol community. In fact, the garden would like to run more school tours, so if you are involved with a local school and are interested in a trip to the Botanic Garden, please contact them via:   www.bristol.ac.uk/botanic-garden