In my previous post I talked about a regenerative planting methodology for urban landscapes, in which I suggested you would manage, rather than maintain your planting areas. So how exactly do you you do this? Both involve work and the difference is a subtle but important one, in both attitude and application. Think urban forester rather than garden pruner. The picture above illustrates this perfectly, so let me explain.
It shows two hazels in my garden, both planted as young bare-root trees in the winter of 07/08. The one on the left was coppiced down to the ground in the winter of 12/13, the other has been pruned to keep a structure of older wood, with all suckering growth removed annually. What is the difference? The coppiced hazel has been less work overall and has not been touched since it was coppiced, the pruned tree has been pruned annually, which was not great amount of work but this is just one tree. If there were a hundred, it would be a different matter. The main difference is that the pruned tree has catkins, the coppiced tree does not, but I think this is a difference of genetics, rather than pruning technique, as they have always been like that. The shape of the pruned tree is also wider in its spread and will become gnarled as it gets older.
So in terms of management, if you go the coppice route you do nothing much to the trees except coppice them every 4-5 years. I would suggest that 50% of the trees are coppiced so that not all structure is removed at once. Notice that the growth of the coppiced hazel is straighter, making for a productive yield of canes and poles that can be used in the local community. Other trees that can be coppiced include sweet chestnut, lime, alder, ash, willow and hornbeam. Birch and oak will coppice, but from young trees only. Willows and dogwoods grown as bushes for their winter colour can be coppiced or “copparded” (inbetween coppice and pollard) to around 300-600mm every two years to keep the winter stem colours strong.
Salix elaeagnos (foreground)
By adopting such techniques in our larger masses of urban street planting and parks, we would deliver a more biodiverse, beautiful and biophilic interaction for all concerned. It would also cost less both to establish and possibly to maintain, than traditional planting. The above willow is beautiful and graceful, yet I have seen it all too often used in municipal car-parks and reduced to a-n-other shrub that is caressed all to frequently with the indifference of a hedgetrimmer.
Time to re-wild our inner selves, and our urban landscapes. We can do so much better than the average landscape we see in our towns and cities.
Posted in Arboriculture, Design, Ecosystem Services, Environment, landscapes, My Garden, Regenerative Planting, Trees Tagged with: adaptive landscapes, arboriculture, biodiversity, biophilia, eco-system services, ecology, gardens, landscape, native plants, pollution entrapment, regenerative landscapes, sustainability, wildlife
Almost all urban landscapes are contrived and designed, due to their artificial nature and short timescales of development and use. We see increasing use of mature rootballed trees and extensive hard landscape and this is normal for intense inner urban areas; I do get concerned that the increasing complexity of urban planting systems divorce trees particularly from their natural functions and prevent the occurrence of the biological interactions/communities that go to make up an ecosystem. For example, I have seen trees planted whose surface levels are around a metre below the surrounding paving level. No matter how well designed, this seems fundamentally wrong to me.
So I’m thinking that there must be a way of dealing with the majority of less intense landscape zones (especially where there isn’t the financial budget that a high-end development attracts) to provide urban regeneration, ecological restoration and biophilic connection, all on a modest budget. This would create a new method to allow for wide-spread adoption in urban and suburban zones. I think the solution comes from Nature’s own process of natural regeneration and a developed philosophy of minimal (but specific) preparation.
silver birch are pioneering species for natural regeneration
Starting from the observation that Nature is very efficient at regenerating itself, what can we do? Too often, I have seen unnecessary interference in this process. I still recall that a few years after the great storm of 1987, I walked through some nearby National Trust woodland of pines and birch. A great deal of damage had been done with many trees blown over. Birch had however, regrown abundantly from dormant seed and was already three or four foot tall. The NT then sent in the bulldozers to clear out the fallen wood so the area could be – replanted. I watched them tracking over all the natural regeneration. Why didn’t they just leave well alone? The restoration of the woodland was only slowed down by such clumsy interference and this was not even a productive forest.
If we simply broke up paving in our urban centres and loosened up the sub-base, what would happen? Nature would soon find a footing and things would start to grow; however, that process would be too slow and unpredictable for human sensibilities. So what if we did a little more, adding a small amount of topsoil to the rubble, planting small (1+1 year transplants) bare root trees and shrubs, with plugs of understory forbs, ferns and grasses. Starting so young, we’d generate a successful community in no time. These could be designed as narrow ribbons – two to four metres wide, inserted into suitable wider areas of paving.
An urban area suitable for natural regeneration
The above area was one I thought would be suitable for such an approach; there are many such areas throughout all urban spaces. They cry out for regeneration, yet seldom can this be done for lack of adequate finance. Below is a quick sketch showing how it might look.
Sketch showing regenerative planting
The benefits of such an approach would be huge. It would cost far less than using a traditional approach to landscaping such an area, maybe half (I haven’t costed it!). The care would move from maintenance to management, using a rotational coppice methodology, rather than trim and tidy (which always ruins a plants natural habit. Biodiversity would be hugely enhanced, air pollution mitigation would increase, wind buffering, urban heat island reduction, stormwater runoff (they would act as rain gardens) and of course, our biophilic needs, our connection to nature.
Someone needs to be bold and try it; talk to me…
Posted in Arboriculture, Biophilia, Climate Change, Design, Ecosystem Services, Environment, landscapes, Regenerative Planting, Trees Tagged with: adaptive landscapes, biodiversity, biophilia, eco-system services, ecology, garden, gardens, landscape, native plants, pm10, pollution entrapment, rain gardens, sustainability, sustainable, trans-migrational landscapes, trees, urban greening, urban heat island, wildlife
Last year some interesting work emerged over the use of green walls for mitigation of air pollution; in particular the ability (or otherwise) of plants to remove particulate matter from the air, with pm10 being the size range focussed upon. This is the particle size most emitted from diesel exhaust, and this does a lot of damage when breathed in.
Like many cities, London is constantly breaching WHO and EU pollution limits and has the threat of a 300m euro fine being levied. Of course, the pollution is nothing like that in the news recently from Beijing, which is largely caused by the low quality coal that fires their electricity generation plants, coupled with cold winter air, which traps pollution in.
So the Mayor’s office set up the Clean Air Fund, and put £5m into research – a tiny amount compared to the fines, but better than nothing. A tiny amount of that was used to put up initially one, then two green walls, which were to be monitored by Imperial College London to see what types of plants trapped the most particulate. Biotecture put the first (and principle test wall) up for transport for London on the side of Edgware Road tube station, right by the Marylebone flyover, one of London’s worst pollution hotspots. The second one was added rather later at the Mermaid Theatre and was done by ANS.
The Green Wall (designed by me) at Edgware Road
I chose 15 species of plants which I knew would take the South facing aspect of our wall and which had smaller leaves – research told me that smaller, hairy leaves were the most effective at trapping particulates, and made sure the species were present across the whole height of the wall. Past research in Germany on Climbers had shown that plants trap more particulates at height, around the 4-5m mark. As it turned out, UCL only collected leaf samples from the pavement level, despite there being roof access where some sampling could be taken, and they only did this for about nine months, so I feel sure that the sample results are insufficient. Nonetheless, they showed a definite ability to capture particulate.
We have barely scratched the surface and what’s needed now are sustained and serious trials to gather more comprehensive results under widely varying conditions and climates… sponsors anyone?
Posted in Design, Environment, living walls, Sustainability Tagged with: Edgware Road, green walls, pm10, pollution entrapment, TfL