Increasing Biodiversity in the Garden

Fri, 05/12/2017 - 15:58 -- Admin

Increasing Biodiversity in the Garden – notes from our recent lecture by Egan Davis

 Currently, it’s considered desirable to bring a bit of wildlife into city gardens; to look at the ecological role of trees & shrubs; to consider native species which are adapted to local growing conditions; to provide a varied habitat for pollinators and birds.

 Egan showed a number of slides with plants in natural habitats, where numerous species grew together in only a few square metres and yet nothing outgrew the others; the “planting” was stable from year to year. These sites included the alpine tundra in northern BC; Harewood Plains, Nanaimo; Eurasian steppe, Romania; coastal dunes, Black Sea; Anza-Borrego, California and many others.

 In many of these locations, the ground is sand, gravel or rock, with extreme (wind, salt, hot, cold, etc) growing conditions. These places have a great diversity in species. Where growing conditions are not extreme, like here in our temperate rainforest, the diversity of species is much less.

 In our gardens, we do too much cleanup, which:

  • exposes bare soil which in turn allows weeds to grow and allows leaching of nutrients & erosion.
  • removes the natural source of nutrients: decomposing plant parts & leaf litter.
  • removes seed heads which could otherwise be a source of food for birds.

 Seed heads can be decorative over winter; dying leaves add colour to the landscape.

 To attract birds to our gardens, you need density of shrubs for the birds to safely move through the area, and to provide foraging & nesting materials.

 Attracting other wildlife: there is a beaver dam in the heart of Vancouver near Olympic Village.

 Attracting insects: bees like blue & yellow colours; butterflies like to have a wide surface to land on like the carrot family; butterflies need protection from wind; double flowers are not as useful for nectar as often the extra petals are modified reproduction parts of a flower; density of flowers is needed for foraging; oregano has built in density with a large number of flowers at once; Steve Reed in Oregon does rotational mowing of lawns with flowers, in drifts of 1/3 every week, in the spring & October... less growth in summer so mowing less.

 We need to understand how soil is built: the top layer is organic litter and insects live there and partly breakdown the litter; fungus & bacteria further breakdown organic matter resulting in a humus layer on top of the mineral soil.

 Examples of Good Diversity seen in the slides of Peter Korn’s Garden (more inventory of species than UBC); Piet Oudolf’s beautiful pocket gardens in Halmstad around social housing that also provide great habitat for nature; RHS, Wisley’s mass perennial plantings by seed; London’s Olympic Park with a South African meadow, a Eurasion meadow & a North American meadow (easy to do but these meadows require replanting); Hermannshof Gardens in Germany; Heemparken in Netherlands; UBC Botanical Gardens gary oak planting which mimics Vancouver Island.

 Sea Blush (Plectritis congesta) is a native annual that germinates in October, grows over winter, flowers in late spring (April) and then dies but self seeds, non-agressively.

notes by: Judy Sullivan, VMG Secretary


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