07 Plants Not to Add to Your Garden
At least not without first finding out what you are getting into.
There are many varieties of plants easily available in nurseries and garden centres around Ottawa that are not ideal additions to most gardens. Below is a list of some varieties which I have often seen lead to disappointment or headaches in the garden.
1. Acer Platanoides Norway Maple
What it is:
Why not to grow it:
This introduced (non-native) tree has a very aggressive root system which is often problematic in small properties and near utilities. It also cast such a dense shade that it is one of the most difficult trees to grow plants under. The biggest problem, though, is its tendency to seed heavily.
These seeds will pop up in your lawn and garden as a veritable mini-forest, and if there are any un-tended or naturalized areas nearby they can become an invasive pest. Toronto has been struggling with this in its ravine parks for many years.
What to plant instead:
Canada is the country of the maple tree, and there are many native varieties to select from without resorting to this introduced variety.
2. Acer palmatum dissectum Cutleaf Japanese Maple
What it is:
Why not to grow it:
Unless you have a completely sheltered yard, with little wind and lots of snow cover in the winter they are just not reliably hardy here in Ottawa.
What to plant instead:
This is always a tricky one since nothing really matches the delicate grace of these maples. For a cut leaf in purple ‘Black Lace’ Elder is often touted as a hardy option, but to my eye the darker colour, coarser leaves and bushier growth, while useful in some sites, is just not interchangeable with Japanese maple.
For a low arching plant, you might want to select and carefully trim cranberry cotoneaster into a low, weeping form, which would be especially effective near a waterfall or stream. If you are attracted by the colour you might want to look into barberries, especially rose glow, which has a pink tone to the young growth and deep purple mature foliage.
3. Betula Birch
What it is:
Why not to grow it:
In urban environments, with their dry, often compacted soil, birch trees are especially susceptible to bronze birch borer, which tunnels between the bark and the wood along the branches and trunk and will eventually kill the tree.
Historically this was treated with an application of a systemic (absorbed into the tissue of the tree) insecticide which was painted on the trunk each spring. Painting a concentrated insecticide on any plant in your landscape is not something that is accepted as common practice anymore, and with Ontario’s insecticide ban the chemical is no longer available for non-agricultural use anyway.
As beautiful as they are, birch is a risky investment to add to your landscape and may lead to disappointment in a few years.
What to plant instead:
For a small tree, I would suggest Serviceberry, which also has a delicate trunk and small leaves which move in the wind. For a larger specimen, you might want to consider a honey locust for dappled shade or a little leaf linden for a denser canopy.
4. Crataegus Hawthorn
What it is:
Why not to grow it:
Unfortunately, these are almost always plagued by rust fungus. Although rarely fatal for established specimens, rust fungus can be quite disfiguring. This tree also has thorns which may be a bit of a surprise for visitors to your garden, since they are usually well hidden among the leaves.
What to plant instead: Disease resistant crab apples such as Makamik, Snowdrift, or Robinson will treat you to blooms and fruit, without the same susceptibility to diseases.
5. Convallaria Majalis Lily-of-the-Valley
What it is:
Why not to grow it:
In most garden conditions this delicate seeming perennial is actually a bit of a thug. It spreads aggressively and has been known to become invasive in natural woodlands. If you are particularly fond of it and would like to have it in your garden I would suggest planting this in a pot sunken up to its rim in the soil.
What to plant instead:
For similar leaves along with airy white flowers, you might want to look for our native Lily-of-the-valley Maianthemum canadense. For a fragrant groundcover, you might like Sweet Woodruff (Gailium odoratum) which has tiny star-shaped blooms in the mid-spring.
6. Fagus sylvatica Purple Beech
What it is:
Why not to grow it:
While readily available here in Ottawa, especially at seasonal garden centres, this tree is not well adapted to our climate. They often develop scorching on their leaves during dry summers, but it is the winter that is particularly damaging.
While this tree can survive in a sheltered location, and the weeping variety is particularly striking, make sure that you have a place to plant it that is sheltered from winter winds and has deep, rich soil.
What to plant instead:
A Weeping Norway Spruce makes a beautiful, dramatic statement, and might fill the space in your garden, if not provided with the purple colouring.
While usually not as narrow as a weeping beech, Royal Beauty weeping crab apples have burgundy foliage and will also treat you to blooms in the spring.
7. Fraxinus Ash
What it is:
Why not to grow it:
Unfortunately, this previously reliable species of trees have been plagued by an accidentally introduced insect called Emerald Ash Borer. There is no effective treatment for the pest at this time, and Ash trees all over the city are currently infected.
What to plant instead:
If you are looking for a low maintenance native tree you might want to try Common Hackberry, which is both droughts tolerant once established and generally disease resistant. If you are looking for a tree with moderately quick growth you might want to consider a Linden, such as ‘Greenspire’ or ‘Glenleven’.
