It may seem simple, and even though this expression has been widely used for decades, do we really understand everything it entails?

This expression also served as the title of a series of lectures givenrecently at the Dominique Savio Nursery as part of training sessions organized by the Association of Green Space Managers of Quebec (AREVQ) and presented by our agronomist Carole Tremblay; here is a summary of those lectures.

If we consider the statement in its simplest form, we immediately think of a high-quality tree—not too large or too small for the planting site—that will withstand the local environmental conditions. But in fact, it encompasses much more than these basic elements. It is therefore important to ask ourselves a series of essential questions, the first of which is:

Why do we want to plan a tree?

Is it to create a windbreak? A screen? A decorative touch? Shade for the sidewalk or the house? Of course, the answer may vary depending on the professional you consult, but it is recommended that you clearly define your objectives from the outset and discuss them with the other individuals and professionals involved in the project (arborists, engineers, architects, urban planners, or simply your neighbor). These questions will spark discussions that will help address the second question:

Where do we plant?

Several constraints may arise at the site, such as the presence of buildings or permanent structures, underground infrastructures (electricity, gas, telecommunications, water mains, etc.), restrictions on site use (e.g., snow storage), existing trees, and so on. Once the site has been selected, a third question arises:

What are the site constraints?

It is important to identify the site’s constraints as precisely as possible; here are several examples that clearly illustrate the importance of on-site observation and dialogue with the individuals and professionals involved:

  • Wind: light or strong? Where do the prevailing winds come from? ;
  • Snow: if there’s a lot of it, are there rodents? If not, is there ice present? If the site is heavily paved (asphalt, cobblestones, or concrete), could the frost penetrate deeper into the ground?
  • Pollution de l’air ou du sol? (et oui, le « jus de poubelle » est toxique);
  • Air or soil pollution? (And yes, “garbage juice” is toxic);
  • Salt spray (splashes from de-icing salt): even if you can’t see it, a highway can generate salt spray over 500 meters, depending on the speed and size of the vehicles;
  • Above-ground and underground obstacles;
  • Maintenance challenges such as snow removal or site uses (daycare, school, proximity to a sidewalk or parking lot, etc.);
  • Quality and quantity of soil available to roots, trampling, drainage;
  • Surrounding plant diversity (Santamour’s rule: max 10% of trees of the same species (e.g., Betula papyrifera), 20% of the same genus (e.g., Betula), and 30% of the same family (e.g., Betulaceae)). Functional diversity is also relevant to consider.

If the chosen location is subject to adverse conditions, it’s best to stick with safe bets, such as the species suggested in the Répertoire des arbres recommandés en milieu urbain published by the IQDHO in collaboration with the AQPP. However, if you want to think outside the box and choose less common species, you should plan to conduct tests and ongoing observations, as new varieties have rarely been tested over the long term before being released to the market. Their hardiness zones and dimensions are, for the most part, roughly estimated based on related trees that are already known. To learn more about new cultivars, it is advisable to consult and compare multiple reference works, as information may vary from one author to another. These sources of information include the following:

  • Specialized publications;
  • Catalogs;
  • Guides;
  • reliable websites (universities, arboretums, research centers, etc.) municipal regulations (prohibited species).

When the time comes, it is essential to plant at the right time and to be able to rely on a quality supply from a trusted nursery. The recommended planting period varies depending on whether the tree is deciduous or evergreen, whether it is being planted in loam or mineral-rich soil, and whether the tree has bare roots, a root ball, or is potted. A trusted nursery is a supplier that can provide trees of the desired size, acclimated to our hardiness zone for over a year, with a well-defined trunk, free of damage, and at least four distinct structural branches spaced at least 15 cm apart. If in doubt, refer to the horticultural standards of the Bureau de normalisation du Québec.

In conclusion, it is important to note that despite all efforts to choose the right tree for the right location, if we do not make every effort to provide the tree with sufficient space and proper care for its healthy growth, no one tree will be able to meet our expectations!