As a ‘card carrying tree hugger’ the last thing I thought I would be doing this spring would be discouraging someone who wanted to plant a tree. But that’s exactly what happened when a friend asked for my advice on which species of tree would be best to replace an elderly silver maple she had lost during a windstorm last fall. It was when she mentioned a preference for installing a willow in her small city garden that I decided a little common sense might be in order.
In an urban environment with postage stamp lots and tiny spaces homeowners should use a certain amount of caution when planting trees, and it is always advisable to do some research about their eventual size and growth characteristics—both above and below ground—before committing to a particular species. Placing a sapling next to a building foundation or under utility lines may seem harmless at first but it may prove to be expensive proposition when it grows to fifty feet or its roots decide to go for a swim in the neighbour’s pool.
So, at the risk of forfeiting my tree hugging status, here are a few familiar species that are just not suitable for planting in small city gardens.
Salix babylonica (Willow)
Willows may not be friends to the urban environment but they do have benefits. Hippocrates described the medicinal uses of willow back in the 5th century B.C and chemist Felix Hoffman successfully pitched a long forgotten bark extract called salicylic acid to his bosses at Bayer which eventually evolved into that useful little pill called Aspirin.
However, plant a willow in the yard and you might have to buy a lifetime supply of the pills to relieve all the headaches these giants will give you because they are notorious for dropping telephone pole-sized lumber in even the slightest breeze. They are also thirsty water-loving plants that have a network of aggressive roots that will travel great distances to sniff out even the slightest bit of moisture. So unless you have a pastoral Downton Abbey type of landscape where its roots can roam and there is no danger of a log falling through the roof of the Rolls, I wouldn’t recommend installing one of these in the garden.
And if tunnelling roots and falling branches are not enough to discourage you from planting a willow, they also come with a suitcase full of folklore and superstitions—most of which are bad.
One particularly ominous old English warning predicts that if the head of a household plants a willow on their property they will meet an untimely end soon after, and the tree will weep for them for the rest of eternity—or at least as long as it is still standing. With that in mind, and if you still want to put one in the yard, it might be a good idea to add to the life insurance policy or hire an unfriendly landscaper to dig the planting hole
Acer saccharinum (Silver Maple)
They are attractive, extremely fast growing and relatively well-behaved as juveniles, which is probably why our city-grandfathers planted them in great abundance as street trees throughout the last century. They are also Canada’s most patriotic tree with one elderly specimen still standing in Leslieville (south of Queen on Laing street) that holds the distinction of being the inspiration for Alexander Muir’s venerable 1867 anthem “The Maple Leaf Forever” Unfortunately, silver maples have been getting some bad press lately because the shallow spreading roots of older trees have been wreaking havoc on drainage pipes, sidewalks and city sewage systems making them a Mr. Roto-Rooter’s dream. Like willows, these moisture lovers also have extremely brittle wood and their multiple stemmed growth habit makes them vulnerable to wind and ice damage, a trait that has earned them the nickname of ‘car crushers’ among arborists who are often called upon to remove the debris from older trees that have dropped in the street or roof of a house.
Juglans nigra (Black Walnut)
Its wood is wildly expensive and highly prized by woodworkers who use it to make everything from furniture, musical instruments, coffins and Lexus steering wheels, which may explain why there have been reports of ‘walnut rustling’ the U.S lately involving chainsaw-wielding thieves sneaking into remote forested areas under the cover of darkness to haul away the tree’s valuable lumber.
While marauding gangs of thieving lumberjacks may not be bold enough to steal trees out of your city backyard, you might soon wonder where your flower garden has gone after you plant a walnut because they are a species that like their privacy and don’t appreciate vegetation competing for water and nutrients. To encourage nearby plants to just pack their bags and disappear, the roots of black walnuts excrete a toxic compound called juglane into the soil which severely stunts the growth of anything that dares to grow within its drip line. Mature walnut trees also produce a prolific number of hard baseball-sized drupes that can dent cars, stain decks and from personal experience, cause a nasty bruise when squirrels start throwing them from great heights in mid-October.
For information on trees suitable for planting in an urban environment and how to get a free tree from the city visit www.toronto.ca/trees/tree_planting.htm. The LEAF organization (www.yourleaf.org) is another resource that has an excellent subsidized tree and shrub planting program in Toronto and the GTA and also offers tree planting advice and site planning.
Steven Chadwick is a professional gardener and horticulturist, and a longtime Beach resident.