Roofs & Rambles

After the extended drought between February and March, the rains came in late May. And with the rains came regeneration. The Forest of viper’s bugloss (Echium vulgare) in early July attracted a flight of bumblebees, carder and honey bees.

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Year of the Spring Drought 2011

The green rosettes of the Viper’s bugloss had laid thirsty, hugged the dry ground of the green roof on the Laban Dance centre. The drought had appeared to kill everything. The grass had turned yellow and most of the other herbs seemed to have withered with the lack of spring rain. But the Viper’s bugloss just rested it’s thirst and waited. The Kidney vetch in the main had been burnt back, though a large patch did manage to survive the drought to be a yellow host to the bees.

The Original Brown Roof

The Laban Dance Centre   ‘green’ roof was the original brown roof or rubble roof. The idea of the brown roof back in the late 1990′s was a slightly irreverent twist on the green roof story. We wanted to mitigate for the loss of brownfield land. At that time the only types of green roof that were acceptable to the building professions were lightweight sedum blankets – of limited ecological value in terms of brownfield ecology. The idea of using recycled building waste and allowing the substrate to colonise addressed a number of issues: cheap!!!, it seemed to have the right ecological integrity (brownfield land often equals a mix of concrete and brick) and self-colonisation would ensure that local plants would arrive and let the roof develop a local character. These principles, though theoretically and philosophically sound, proved to be slightly erroneous. For one concrete is not a good green roof substrate, as it does not hold much water. Self-colonisation generally leads to highly invasive and unwanted plants arriving on the roof. Some of which could seriously compromise the integrity of the membranes. But the brown roof term had been coined and it is now ‘embedded’ in the culture of green roofs in the UK. As one of the people who coined the term I wish I could kill it dead. I have tried to re-define what constitutes a good ‘brown’ roof – a blended commercial green roof substrate to support wildflowers and seeded with a range of wildflowers and sedums. But this may take years to change. Eco dumping construction waste of roofs serves the contractors in terms of cost-cutting and winning contracts, and many, to be frank, have little interest in the  biodiversity of the green roof.

A Green roof Success?

So the Laban Dance Centre has been a lesson. Yet it still surprises. After two years of spring droughts, has killed off many of the invasive grass species and buddleia and fleabane and sadly a few of the interesting herbs. But what has survived these extended periods without rain has seeded. And those seeds are creating a robust ‘breed’ of plants conditioned to the harsh realities on this particular roof. Over the years we have recorded over 100 species of higher plants on the roof, which is more than most green roofs have!

The forest of Viper’s bugloss is a wonderful site to see in July. And with the bugloss come the bees. We counted four bee species on the roof – White-tailed and Red-tailed bumblebees, Honey bees, Common brown carder bee and also a collates species actively foraging from the plants. Other herbs had survived the drought though in lesser numbers, Kidney vetch, clover, St.John’swort, Lady’s Bedstraw, Hare’s Foot Clover and a few lucerne. Where once there had been a sea of Ox-eye daisies there is only a pair, and a few chives have managed to keep a foot hold are still blossoming. But these plants will seed and next year, depending on the weather, we will see further renewal. The roof is now 11 years old and has been monitored for bugs, bees and spiders for 10 of those years. It has been through droughts, wet years, frost, snow nearly everything the British weather has thrown at it. And it still there and is still awash with grasshopper’s and home to foraging bees. And it is roof that gives me a great deal of angst when there is no rain but a great deal of joy.

It is one of the many I have been directly involved that I immensely proud of.