Restoring Endangered Habitat in the Urban Landscape

Published in Landscapes/Paysages, Issue Summer 2001 Vol. 3/ No.1. Canadian Society of Landscape Architects

Initiated by a hospital’s need to create a multi-storey parking structure adjacent to a remnant stand of Garry Oak * (Quercus garryana), the landscape priority was to ensure retention of as many trees as possible while improving the quality of the landscape both as Garry Oak habitat and as a therapeutic garden for long-term care patients.

PD Group, working closely with Arbour-Care Tree Conservation Services Ltd. and PBK Architects Ltd., has married an innovative approach to the restoration of natural Garry Oak habitat with the creation of a therapeutic garden at Royal Jubilee Hospital, Saanich near Victoria, British Columbia.

The existing stand of oaks was in decline—the result of previous “beautification” efforts and a surfeit of hardscape and turf. Our design response required a thorough investigation of native Garry Oak habitat. The findings pointed to two potential approaches: one which creates a managed understorey of grass and wildflowers including Greater Cammas (Camassia leichtlinii), historically an important food source for First Nations inhabitants of the area; or one which creates a native shrub understorey. The latter option was discounted under the existing trees due to the potential root system damage from planting. A combination approach provided a low-impact solution under the trees while native shrub groupings give spatial definition to garden spaces outside critical root zones.

The restoration specification included the careful delineation of protected root zones, on-grade pathways and temporary construction access that spanned protected root areas. Extensive mulching with oak leaf mulch was considered essential for efficient nutrient cycling. Unusual native bulbs (some bulbs divot-planted and some as seed), shrubs and grasses were features of the comprehensive planting approach. New Garry Oaks have also been added responding to the lack of natural regeneration of the species. Sources were researched early and included for bidder information within the tender package, in order to minimize inevitable requests for substitutions of harder-to-obtain native plants and seeds.

Therapeutic elements of the project include a walkway carefully threading around the established trees. Benches are positioned to allow users to pause to enjoy their surroundings. Gardening activity stations built around raised “planting troughs” serve wheel-chair bound patients.

To mitigate the scale of the new building’s concrete shear walls, 9.0m high Douglas Firs (Pseudotsuga menziesii) and 6.0m Serbian Spruce (Picea omorika) have been installed giving immediate visual relief to the building mass. Although most of the plant palette is drought-tolerant, an irrigation system meets the establishment requirements of these plants on an urban site where the natural hydrology has been disrupted.

Ecosystems dominated by Garry Oak are considered endangered and greatly at risk of loss from British Columbia. They are restricted to the south east coast of Vancouver Island and the Gulf Islands. Garry Oak woodlands support the highest diversity of any terrestrial ecosystem in B.C. The British Columbia Conservation Data Centre (CDC) rates the ecosystem and many of the plants and animals it supports as “critically imperiled”. For example, 20% of rare plants in the province live only in the Garry Oak ecosystem.

The project was completed in November 2000. The development of its unusual landscape will be an ongoing process, dependant in no small part on the maintenance input during its early years. Maintenance requirements have been reviewed in detail with grounds maintenance staff and the expectation is that the site will flourish naturally as intended. The response from hospital staff and neighbours has so far been positive. Patience will certainly be required as some of the wildflower seed is expected to take up to six years or more to flower!

David Rose, CSLA, is a principal in the firm PD Group Landscape Architecture & Interior Design Ltd. based in North Vancouver. The landscape division specializes in healthcare, parks, schools and memorial gardens.