Topic 4 Risks and deviations over biodiversity plans in green roofs(control of plagues, weather extreme conditions…)

Regarding the design strategies to maximise Biodiversity, it is recommended to establish design strategies to enhance biodiversity and natural colonization on green roofs.

Birdsfoot trefoil.  A native wildflower that is invaluable for bees

Often found growing in lawns, this low-lying plant is part of the pea family and produces a mass of yellow flowers in summer, which then develop into seedpods. Ideal as a green roof plant, birdsfoot trefoil is rich in pollen, so a favourite for bees and butterflies.

Recommended green roof growing medium parameter ranges


  • Emphasize native species
  • Any non-native species used should be non invasive
  • Review suitable plant species including end points and life cycle needs for targeted species
  • Select grasses and herbaceous plants that produce numerous seed heads that can provide invaluable energy sources for migratory birds


  • Position substrate near building sites before elevating to the roof if practical (species can inoculate substrate at grade level)
  • Incorporate local materials in substrate blends (compost/porous materials)
  • Use compost liberally where practical
  • Vary substrate depths and drainage regimes to create a mosaic of microhabitats on and below the soil surface that can facilitate colonization by a more diverse flora and fauna
  • Vary substrate depths by adding berms/mounds, bare areas, and physical substrate connections to enhance species movement (promotes heterogeneity)
  • Control the values of components of ground (see table in this page)


  • Add bird boxes, bat boxes, and trap nests for bees as desired
  • Add snags (tree limbs) and stones for terrain variation and moisture retention
  • Add depressions to collect rain water for short periods