Creating biodiverse extensive green roofs by planting native species in natural associations

Background/Question/Methods

There is increasing interest in green roofs, including extensive green roofs, which are roofs that are usually not irrigated and vegetated with low-maintenance, drought tolerant vegetation. The horticultural industry has responded to the challenge of providing vegetation for extensive green roofs by encouraging the use of simple swards of plants of the Sedum genus, often using non-native species, and often pre-grown on blankets and mats. Although this approach provides a uniform vegetation cover with a predictable appearance, the ecological value and species diversity is often limited, something that has been shown through invertebrate surveys undertaken during the past decade in Switzerland and London. This presentation will investigate the desirability and possibility of creating more biodiverse extensive green roofs by planting and seeding native species which occur in natural and semi-natural arrested pioneer communities, which provide conditions which are similar to those found on roofs.

Results/Conclusions

Biodiverse extensive green roofs vegetated with native species have been created and monitored in Switzerland and England. These have been shown to be more biodiverse than Sedum dominated blankets or similar monocultures. The case will also be made for this approach to be replicated elsewhere, in temperate, Mediterranean and other climates, using locally appropriate native species planted in natural associations.