How many trees?


I live in a 3 year old two-storey home in North Oshawa. I would like to plant some trees in my backyard. The yard is about 12 metres wide and 9 metres deep. It is on the north side of my house. The house causes a permanent shadow 2 – 4 metres long depending on the time of year. The area near the back fence is in constant sunlight. The soil is clay.

Trees I was thinking of planting include Serviceberry (Ballerina, Autumn Brilliance, or Princess Diana), Kousa Dogwood (Milky Way), and/or Paperbark Maple. From what I’ve read, they all grow about 5 metres wide, though the Dogwood eventually has a rounded form and the others more upright. How many trees of this size would be reasonable to fit in my yard? How close together can I plant them? If I chose to plant one closer to the house, is one species better suited to this than the others? Thanks.


Dear Gardener,

Thank you for asking these questions, especially as this is the time of year when many other readers, as well, will be wanting to make decisions on spring tree planting. In my mind’s eye I can visualize the graph-paper plan you have drawn as a planting guide for your well-researched selections !

Regarding planting near shaded areas, the Kousa dogwood, Cornus kousa,  is a uniquely colourful tree that can grow equally well in full sun to partial shade. And, as a tip, dogwood shrubs, too, can develop as wonderful flowering specimens. Next, the Amelanchier species of trees, of the Rosaceae family, known as the serviceberry, is a much-loved native North American tree that is available in several species and hybrids. One that you mention, the Amelanchier × grandiflora ‘Princess Diana’, can also thrive in sun to partial shade.  So either of these might manage well if planted closer to your house.

However, the show-piece Acer griseum, Paper Bark maple, with  exotic cinnamon-brown, exfoliating bark, also well-suited for smaller gardens, is generally noted to thrive best in full sun, further out in your yard.

Regarding your definitive comment ” the soil is clay”, I’ll take it that there’s a high percentage of clay in your yard. Your home is relatively new, and often contractors are not responsible for ensuring that rich, fertile soil fills the surrounding lots. Considering that you’re making a significant investment in these plantings, you may wish to test your soil. This way you can plan for whatever soil amendment is required. Healthy soil for trees, and all plant life, is made up of plenty of microorganism activity, adequate water drainage, and good oxygen flow. A soil test will tell you the Ph composition, and what nutrients you need to add to improve your soil, including nitrogen, phosphorus and potassium. While all three of your tree choices could possibly grow to be fairly Ph adaptable, the very best advice would be to give them the optimum growing conditions right from the start, and promote them to thrive for many years as healthy, robust features to your home garden.

Fortunately, simple soil testing kits can be purchased at most garden centres. Alternatively, the Ontario Ministry of Agriculture and Rural Affairs (OMAFRA) has a list of accredited soil testing sources on their web site:

Lastly, how many trees will fit in your yard? And how close to plant them?  I’m going to suggest that you consult this thorough, must-read TMG Guide  titled “Planting a Tree”, which addresses the many factors to consider, including:  space, light, soil, water and wind conditions.

If you wish to make an appointment with a registered arborist, please contact Landscape Ontario, where you can easily locate and contact professionals close to your area.
All the very best with your spring landscaping project !