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Wednesday, 24 October 2012

Autumn in a new light

     Some of my fondest memories of autumn are as a child holding my parent’s hands on a crisp afternoon, watching as my little red welly boots swished through the dried fallen leaves of the season. Even now as an adult, I can’t resist shuffling a little when conditions are right, just so I can watch the warm colours roll across my feet and listen to the rustle of autumn. However, last Friday Nick Wray, Curator for the Botanic Garden, opened my eyes to a whole new set of autumn delights – from winged bushes to exploding seed pods – this season is about so much more than just falling leaves.

Fruit and flowers
The small orange fruits of G. tinctoria
     The first stop on our tour was the plant Gunnera tinctoria, which to the untrained eye looks very much like rhubarb on steroids, and as a result is commonly called giant rhubarb. This species is smaller than the one commonly seen in British gardens, Gunnera manicata, but otherwise looks the same. As the plant prepares for its dormant winter phase, the large leaves have started to bend to the ground, revealing a world of colour beneath. Wrapped in a sheath of red feathery tufts are the promises of next year’s growth – buds, which will grow over the winter months ready for next spring. Beside these are the large influorescences, rising up like staffs from the base of the plant. Here, thousands of tiny orange fruits are housed, each one the product of a tiny pollinated flower.
     Growing on the north side of the house, in constant shade, is proof that autumn is still a time for flowers – Begonia grandis. This is a woodland plant from southern China and its pretty pink flowers are only one part of this plant’s colourful display. Turn the leaves over and an extraordinary cinnamon red is revealed.

Flower of B. grandis with the colourful dark underside
of the plant's leaves in the background. 
“This is an evasion strategy,” Nick starts to tell me, “plants can’t get up and run away from predators, but they can masquerade as something else. Herbivores mooching about through the understory are likely to think there’s something wrong with this plant as the leaves make it look as though it’s dead or dying.”

Nick then takes me around the corner to one of his favourite plants in the garden, Impatiens tinctoria – a balsam. I can instantly see why it’s a favourite as the flower is truly stunning. Native to the mountains of western Ethiopa, this plant is adapted to cold dry winters and warm wet summers. The plant towers above me and Nick tells me all this growth has happened since the second week of May – an extremely fast growing plant indeed!
Flower of Impatiens tinctoria.  
     This plant has been producing flowers since July and they are clearly built for bee pollinators. A deep crimson runway guides the bee toward its nectar reward and as it enters the flower, its back rubs along the anther, dusting it in pollen. The pollinated flowers produce a rather extraordinary seed capsule, which is of course another important aspect of autumn....dispersing the next generation.

Scattering seeds
     Like all balsams, I. tinctoria has an explosive seed capsule. Each one is about 3cm long (just over an inch) and resembles a tiny cucumber. Water pressure keeps the capsule extended, but when a little force is applied, the sides of the capsule spring into their natural curled state of repose and the seeds are literally catapulted out. This explosive dispersal method is partly why Impatiens is very successful as a genus. However, this beauty is not to be confused with Impatiens glandulifera (Himalayan balsam), which was introduced as a garden ornamental by the Victorians and is now found choking many of the waterways throughout the UK.
The bladder-like fruits of Colutea arborescens
     Another wonderful example of autumn seed dispersal in the garden is the Bladder Senna, (Colutea arborescens). Though this plant doesn't bring any colour to the garden at this time of year, the fruits offer their own element of intrigue. Native to the Middle East – Turkey, Iran, Iraq – the beige fruit resembles slightly deflated balloons dangling from the branches. Open it up, however, and inside you find two rows of perfectly paired little black seeds. As winter approaches, these fruits will fall off the tree and be carried across the dry land by the wind, much like tumbleweed. As the fruit tumbles along, it starts to tear and break down and the seeds get released. This type of seed distribution is very successful, particularly in the seasonally dry climates where it is found.

Losing leaves
     Besides the fruits, flowers and seeds, there is no denying that the Botanic Garden also offers a colourful display of leaves at this time of year. All the autumn colours are represented – yellows, oranges and even vibrant reds.
     As the days get shorter, many plants stop producing a type of plant hormone known as auxin. Among their many roles, auxins prevent a specialised layer of cells at the base of the leaf stalk – the abscission layer – from developing completely and cutting off the internal tubes that connect the leaf to the rest of the plant. So, once auxin levels drop, the abscission layer functionally cuts the leaf off from the rest of the plant. The chlorophyll, which gives the leaves their green colour, disintegrates rapidly revealing the other pigments carotene and anthocyanin, giving the leaves their autumn colours.
The bright orange seed of E. alatus seems dull compared
to the vibrant colour of the leaves
     Nick brings me over to Euonymus alatus, the colour of which almost hurts the eyes. The leaves are a fiery fuschia colour. This species is from China and it gets its name alatus, which means winged, from the hard sharp protrusions from the stem that protect the plant from herbivores. In the summer it’s a pleasant green shrub, but this time of year it is ablaze with colour. If the leaves weren’t enough, scattered throughout the bush are tiny fruits, which have split to reveal a single bright orange seed – a delicacy for birds.
     Other plants, such as the witch hazel, (Hamamelis mollis ‘Pallida’), don more golden hues but are no less spectacular.
H. mollis glowing gold against the evergreen backdrop
of Atriplex humilis (Fat Hen family)
     Nick had to run to a meeting, but I stayed in the garden for another half hour, taking photographs and crouching down to look at plants from new angles and examine parts that are usually hidden by lush foliage any other time of year. It was a whole new way to experience autumn. Of course, I still shuffled through the fallen leaves on my way out...some things are sacred.



Remember - next weekend (26th-28th October) is the 25th British Orchid congress at Writhlington School!

Wednesday, 17 October 2012

“WOW! That’s a lot of bees!”


     I could hear my son’s enthusiastic voice coming from somewhere near the front. He had managed to squeeze through the crowd so he could see, while I stood at the back trying to catch a glimpse of what was going on. There were about a hundred of us gathered around a demonstration beehive in the University of Bristol’s Botanic Garden, listening to the beekeeper talk about maintaining beehives. He’d just pulled out a frame from the hive that was absolutely writhing. We all stepped in for a closer look, and despite having no fear of bees, I have to admit that I was grateful for the mist net that separated us. After all, 15,000 is a lot of bees!
An audience gathers around the demonstration hive to
learn about the art of beekeeping. Photo: Nick Wray.
     Last month, my son and I were on a long walk when we happened upon the annual Bee and Pollination Festival at the Botanic Garden. The festival is a joint effort between the Botanic Garden and the Bristol branch of the Avon Beekeepers Association and this was its 3rd year running. This year, the event also partnered with the Bristol City Council’s Allotments Team, who helped to build a small working allotment on-site to celebrate the event’s theme of vegetable growing and allotments. About 1,000 people visited the gardens over the festival weekend and judging by the faces gathered around the demonstration hive, it was a hit whether you were two or ninety-two.
     For my 4-year old, bees mean delicious sweet golden honey. However, for many of us with gardens or allotments, bees have a much greater importance and value in their role as pollinators and the Bee and Pollination Festival was a chance to celebrate this. In the UK, the hard work of pollination is mostly done by insects – bees, butterflies and hoverflies to name a few. Besides our domestic bee, Apis mellifera, the UK has 26 species of bumblebee and 250 species of solitary bee. While we’re at work making a mental list of things that need sorting out in the garden on the weekend, these pollinators are out there doing their thing. In the UK alone, the value of insect-pollinated crops is estimated to be £510 million annually; pollinators perform an extremely valuable ecosystem service that is critical to our future food security.
     It’s important to be reminded of the connection between food and insects, particularly when we consider the plight of our pollinators. Bee and pollinator populations are in decline largely due to loss of natural habitat; monoculture crops and well-grazed pastures do not promote the wild flowers that are essential food for our pollinators. Loss of nesting areas, widespread use of pesticides and disease are also taking their toll.
     The University of Bristol’s Urban Pollinators Project was on hand at the festival to discuss some of these issues. The project is taking a close look at pollinators in urban environments, surveying pollinating insects in the urban centres of Bristol, Edinburgh, Leeds and Reading. The researchers are comparing the biodiversity of pollinators in urban environments with that in reserves and farmland. They’re also trying to identify urban hot-spots of pollinator biodiversity and look at ways of improving diversity and abundance of pollinators in urban areas.
The small working allotment built for the Bee and
Pollination Festival. Photo: Nick Wray.
     While my son stood entranced at the observation hive, searching for the queen, I also had a chance to check out the Bees for Development stand. If you haven’t heard of them, this is an independent organisation that works largely in Africa and Asia promoting more and better beekeeping to help build sustainable livelihoods in developing communities, while also conserving biodiversity. Among other things, the group helps promote the value of bees as pollinators, linking beekeeping to improved crop yields and profits for farmers and stressing their importance for food security.
     We had unfortunately just missed a speaker from Writhlington School’s Orchid Project, but we did meander through the artist exhibits and local nursery displays. We stopped by the Riverford Organic and Butcombe Brewery displays, and of course we couldn’t leave without buying a jar of local honey from the Bristol Beekeepers.
      However, the highlight of the day for me was, without a doubt, seeing my son’s face as he wound his way through the crowd to find me and share his unbridled excitement at seeing all those bees. For him, the smell of the smoke, the hum of the bees and the thrill of spotting the queen among thousands of dancing bees was an incredible window into the world of bees. For me, it was a reminder of the many ways we’re connected to insects and pollinators in particular. For both of us, we’ll have fond memories to think back on each time we enjoy some of our local honey.