Roofs & Rambles

This is one of the most remarkable green roofs I have ever visited. The roofs are all about 15 years old. In pure construction terms they could be considered ‘not very good’. However what a constructor or conventional green roofer might consider ‘poor’ installation, an ecologist or botanist would marvel at. I certainly did.

It is kind of strange that trying to get green roofs on hospitals in the UK has often caused concerns – health issues. Many hospitals in Switzerland have green roofs. The one I am most familiar with is the KantonHospital Basel. However the KantonHospital St. Gallen is a real wonder.

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What is amazing is not only the profusion of green roofs. Every roof seems to have some vegetation but the amazing display of orchids.

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What is even more surprising is that they are growing on a very thin substrate – about 50mm. The main orchid roof seems to mot drain very well, therefore the substrate remains very moist, Furthermore the roof is in sun shadow so doesn’t tend to dry out at all. Hence the ability of the orchids to survive. According to my colleague Dr. Stephan Brenneisen, the local city nature conservation officer was amazed when the roofs were pointed out to him!

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However, although the orchids steal the visual show, it is the assortment of other plants that draw the connoisseurs eye – mosses, club mosses and also a number of carnivorous plants normally associated with wet heathland. The water retention of the substrate due to poor construction and drainage has meant has meant that the roof as ‘huge’ mounds of moss that have accumulated over the years.

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Elsewhere on the roofs, where exposed to the sun and the wind, and where presumably the construction was ‘better’ in conventional terms, sedums and more traditional herbs associated with green roofs flourish. There are also a few roofs were spontaneous low woodland has been created.

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I will write about this roof in more detail at a later stage but for now the diversity of habitats and plants make this definately a a green connoisseurs green roof wonder.