By: Vancouver Sun
Bill Stephen, tree expert with City of Vancouver’s urban forest strategy team, wants to show me how hard it is to take care of trees in the city’s downtown core.
We meet at the corner of Carrall and Water streets in bustling Gastown and Stephen points to a beautiful row of maples planted along the sidewalk.
There are at least five varieties of maple planted along a short strip that runs past Trounce Alley — Autumn Flame, October Glory, Silver Maple, Field Maple and Red Sunset Maple.
Planted 45 years ago, they all look sensational with canopies offering a charming range of colours from soft pink and red to amber, yellow, and shades of rust and orange.
“It’s easy to grow trees in Stanley Park, but it’s not so easy to get trees established and keep them healthy here where there is a lot of traffic with a continual stream of cars, bicycles and pedestrians,” Stephen says.
“Our goal is to protect, preserve and manage these trees to make sure they continue to create this beautiful environment.”
Stephen says when he looks at one of these trees, he is thinking just as much about what is happening underground with the root system and soil composition as he is about the branch structure and esthetics.
“We have had put up metal barriers around trees most prone to being damaged. We have also put down drainage grids made of recycled tire rubber to create a soft carpet around the tree that is both fast draining and easy to walk on. We do everything we can to keep these trees happy and alive.”
Vancouver is fighting a battle to save and enhance its urban forest — trees, large and small, on both public and private property that do so much to make the city a pleasant place to live.
The city’s overall tree canopy has shrunk by five per cent from 23 to 18 per cent over the last two decades.
In a bid to reverse that trend and start to increase the urban forest and its overall tree canopy, the city aims to plant 150,000 new trees by 2020.
About 37,000 trees have been planted so far — 11,700 of those this year. Although the program was revved up, thousands more trees will need to be planted each year to meet the goal.
“Tree canopy is very important for a number of reasons,” says Stephen. “Shade from the trees reduces the negative impact of what we call the heat-island effect.
“Without tree cover, areas get significantly hotter in summer. Direct sunlight in conjunction with car fumes can create a lot of airborne pollutants. The result is an environment that is less comfortable to live in.”
Tree removal has been a big reason for the loss of trees. Many have been removed to make way for new construction.
The city’s tree bylaw does require that if a mature tree is removed, a new tree should be planted in its place, but this rule doesn’t always work as effectively as it should.
“When a big tree is taken down, we lose a lot of tree canopy. But we are also seeing smaller trees mature and develop and that growth accounts for about a three per cent (per year) increase in tree canopy,” says Stephen.
A 2014 city report identified key areas of the city with the best and worse tree canopies.
Districts with the most tree coverage include Dunbar/Southlands with 28.1 per cent and West Point Grey, Shaughnessy, Kerrisdale and Killarney with 23.9 per cent. The West End has 18.6 per cent.
Areas with the skimpiest tree cover include Strathcona (5.9 per cent), the downtown core (8.3 per cent), and Renfrew and Collingwood (9.7 per cent).
“We are taking great care to strategically plant new trees in these areas. We want to do it right, so that they grow slowly and last for a long time,” says Stephen.
“The challenge is that these are densely developed areas and we also have to consider what is going on underground.
“It is so important to make sure trees get the right soil protection when they are planted and that there is plenty of room for healthy root development.”
Vancouver’s urban forest comprises 140,000 street trees, mostly maples, cherry and plum, plus 300,000 park trees and countless others on private property, including thousands of gardens.
“Our city has the most diverse tree population anywhere in Canada, with more than 500 different kinds of trees,” says Stephen.
When he began working in the city’s tree department in the early 1990s, trees, such as ash, linden, beech, oak, chestnut, maple and cherry were commonplace.
Katsura and parrotia were not widely planted. Neither was styrax, Magnolia kobus or Korean dogwoods (Cornus kousa).
“These have all been added over the past 30 years. Parrotia ‘Ruby Vase’, for instance, has turned out to be a first-class street tree.
“It starts with branches growing upward and then flattens out into an umbrella shape. It provides great shade in summer without interfering with people or traffic below. It also has beautiful fall colour.”
Columnar hornbeams have also proven to be a very good tree for planting along streets with heavy traffic.
Lindens, however, have become problem trees because of their proclivity for becoming infested with sticky aphids.
“Slowly, we are replacing our problem trees with better trees. But it takes time. We are not going to remove a tree just because it is a problem for a short time.
“We treat nuisance trees as best we can with soap sprays and predatory insects but in most cases the problem is temporary. These kinds of trees represent a very small percentage of the total inventory.”
Stephen says he is particularly fond of the wedding cake tree (Cornus controversa variegata).
“We try to plant it whenever and wherever we can. It is an exquisite tree.”
He is also likes the Korean mountain ash (Sorbus alnifolia), also known as the alder-leaf whitebeam.
Many trees are grown from bought saplings at the city’s nursery facility in Langley where an inventory of about 7,000 trees provides between 1,500 and 2,000 trees for planting every year.
Stephen says he is continually looking for good places on city property to plant new trees, especially golf courses and parks.
“The focus is always to plant ideal trees strategically and properly to get the maximum benefits. We have many pockets in Vancouver that are being under-utilized.”
Keeping newly planted trees alive is another challenge. Weed-whackers and lawn mowers kill a lot of newly planted trees by damaging the trunks, which can lead to disease.
Watering is another big issue, especially during hot dry spells. Homeowners can help by deeply watering baby trees once a week during summer.
“Once a young tree gets its roots established, it can thrive without much help, but it is always good to help juvenile trees during their early days.”
Next month, city council will again look at its urban forest strategy and its goal to be the “greenest city”.
I’m sure it will be hoping gardeners will help by seeing if they can find room for one more tree in their garden. Every bit helps.
By: Vancouver Sun