Grading the green roof on Vancouver's new convention centre
Grading the green roof on Vancouver's new convention centre
It's been three years since it was complete, so is Canada's biggest green roof a success?
The green roof on the Vancouver Convention Centre comprises 25 different species of native plants, mostly grasses, but also perennials, such as Douglas asters that grew taller than expected.
Photograph by: Handout photo, Vancouver Sun
It's been three years since the green roof was planted on Vancouver's new convention centre.
Is it a success? Is it as good as they promised it would be?
The answer is that some parts are terrific - attractive, quality planting; a beautiful habitat for songbirds and insect life.
But other areas are untidy, scrubby, a bit of a mess; you might even say, an eyesore, and a fair ways from what they could or should be.
Overall, the roof is more a success than a flop, but there's definitely room for improvement, so the designers should not spend too much time pat-ting themselves on the back. There's still some refining work to do.
Covering 2.4 hectares (just over six acres), it is still the largest living roof in Canada and the largest non-industrial green roof in North America.
But being 10 storeys above ground, you can't see much of it from street level, say from outside the Fairmont Pacific Rim at Canada Place.
The roof is mostly visible to people working in adjacent highrise office blocks or living in luxury condos opposite.
This lack of public access was always one of my main criticisms of the roof design - its failure to incorporate sufficient access for the public to get up there and actually enjoy the views.
Would it have been so hard to create a garden-like viewing area where people could see the meadow on the roof as well as panoramic ocean views?
There is access via an elevator and sloping walkway to a small raised viewing platform over the plaza with the Olympic cauldron below. From here, you can see a larger portion of the roof. On your way to this platform, you pass a series of raised concrete planter boxes filled with a mixture of ornamental grasses, boxwood, perennials and anchored by maple trees.
The planters set an appropriate for-mal, elegant tone for the plaza and create a more natural transition to Harbour Green on the waterfront at Coal Harbour below.
The route to the viewing platform also takes you past beautiful borders, lushly planted with feather reed grasses (Cal-amagrostis), fountain grasses (Pennis-etum) and miscanthus grasses.
All these elements are excellent. However, the highly-visible areas immediately next to the walkway up to the viewing platform are a bit of a dog's breakfast. They look scrappy, weedy and neglected. Not really good enough for a world-class facility.
Bruce Hemstock, landscape architect with PWL Partnership in Vancouver, the firm responsible for the green roof, says these areas were specifically designed to give "everyone the opportunity to see the plants that form the urban habitat" - the plants used on the roof.
"There tends to be a lot of foot traffic over the low wall. This has resulted in compaction of the growing medium and a bit of a tougher environment for the plants to grow."
Nevertheless, it is still such a prominent area that it ought to be more of a showcase with a much more creative composition of rugged all-season plants; ones that should provide a tapestry of colour and interest throughout the year - sedums, thymes, heathers, short ornamental grasses, compact perennials, sempervivum and easy-maintenance ground covers.
The green roof proper has grown into a shaggy, rough-looking meadow, intersected by a few narrow gravel footpaths, primarily as access for maintenance crews.
More than 400,000 native B.C. plants representing 25 species were used to cover the six acres of roof space. In addition, 40,000 bulbs were planted and 128 kilograms of flower and grass seed sprinkled to create the equivalent of the "coastal grassland," the kind of look you are most likely to see on the exposed northern tip of Vancouver Island.
The best part of the roof, to my mind, is an area where 80,000 sedums have been densely planted to form a massive carpet of colour and texture on the sunny west side of the building.
Unfortunately, this is not visible to the public, except on a special tour.
The roof's wild-meadow look has been achieved by planting mainly three types of common grass - Idaho fescue (Festuca idahoensis), red fescue (Fes-tuca rubra) and Quatro sheep fescue (Festuca vugaris).
In spring, these quickly rebound to produce a lush habitat for songbirds and insects and resting ground for seagulls and Canada geese.
Dozens of wildflowers, including Douglas asters (Aster subspicatus), nodding onion (Allium cernum) and common camas (Camassia quamash), have enabled bees from four hives to produce 120 pounds of honey.
Hemstock says when he makes presentations around the world about the roof (as he did last week in Australia), the questions he gets asked the most have to do with maintenance.
The grass on the roof is mowed once a year. Maintenance crews also make weekly visits to check drainage lines and to pull out invasive weeds.
Would the roof have been easier to maintain with a different planting scheme; perhaps by not using grasses that need to be mowed at all but by using more sedums, compact bulbous plants, a careful selection of low-growing ornamental grasses, plus more easy-care ground covers and perennials?
It would certainly have made a more visually interesting roof. Maybe part of the roof should be used to conduct some experimental planting schemes? As for the roof's current esthetic, Hemstock says it has exceeded all his expectations.
"The natural qualities of the grasses and native herbs blend well together. There are enough hints of colour throughout the year to provide interest but not so much that it looks contrived".
Would he do anything differently? "I am happy to say no. I would not change anything. This is one of the few projects that I feel comfortable making this statement".
In North America, the roof has set a high standard, he says.
"From what I have seen and have been told, it is right up there with some of the best ecological roofs built in England, Germany and elsewhere in Europe.
"The project continues to get a lot of attention because it strikes at the heart of an issue that we all hear about and are interested in - global warming and the loss of habitat through urbanization".
YOUR GUIDE TO THE PLANTS
Plants used on Vancouver Convention Centre roof:
Agrostis pallens (bent grass).
Anaphalis margaritacea (pearly everlasting).
Allium acuminatum (Hooker's onion).
Allium cernuum (nodding onion).
Armeria maritima (thrift).
Aster subspicatus (Douglas aster).
Brodiaea coronaria (harvest brodiaea).
Brodiaea hyacinthina (fools onion).
Calamagrostis stricta (reed grass).
Camassia quamash (common camas).
Carex densa (dense sedge).
Carex pansa (meadow sedge
Carex tumulicola (sedge).
Carex pachystachya (sedge).
Eschscholzia californica (California poppy).
Festuca idahoensis (Idaho fescue).
Festuca ovina glauca (blue fescue).
Festuca ovina vulgaris (sheeps fescue).
Festuca rubra (red fescue).
Fragaria chiloensis (beach strawberry).
Koeleria macrantha (June grass).
Potentilla anserina ssp 'pacifica' (silverweed).
Sedum spathulifolium (stonecrop).
Sisyrinchium bellum (blue-eyed grass)