The recent popularity of creating vegetable gardens is a welcomed and noble notion, but gardeners should take heed of the potentially significant damage a new garden can cause to roots of nearby trees.
Soils in cities are generally shallow and frequently consist of compacted sub-soils. As a result, tree roots are dependent on the same 6-foot-deep soil mass that is now to be repurposed for the veggies to grow in.
A better, simple solution (in which both the tree and veggies will benefit) would be to bring in new soil to top up and spread out at the site location, taking care not to cover or bury existing tree roots, before planting veggies in mounds.
In this way, you will increase the depth of soil – not to mention visual interest if your lot surface is flat. The new raised soil beds will provide healthy aeration for seedlings' roots to quickly grow into, thus producing stronger crops, and it will be more quickly warmed by the spring sun.
These beds can be prepared with high organic matter to better absorb water (making it available to the growing veggies) and, also, for better drainage when there is excess – thereby achieving the ideal balance of water and air availability that should last throughout the outdoor growing season.
If there is an extensive tree canopy that limits sunlight, then pruning can be done as long as it’s limited to 10% or less of the limbs per year in order to avoid shocking the tree in our tough Canadian climate.
In that case, remove the lower limbs first (the tree would naturally drop those in time anyway), which will allow the tree to focus on new growth in its upper canopy. The loss of these limbs will not affect the tree too much and will allow light to pass under the canopy. This technique is called "raising the crown."
If you are fortunate enough to have several trees on your property giving you a complete shady canopy over your home and garden, the best option would be to remove one single tree. This creates an open space in which to place your veggie beds, and enables the other trees to still thrive.
Trees in cities are so valuable to our health and in cooling cities that their health must be our priority. By adding healthy soil to new projects, we can have both. If we notice and focus on the roots of all plants, we will understand how to have happy plants growing beside us at home. 🌳
Read last month’s blog “How Lawns Kill Trees” to learn about the detrimental impacts that lawns have on tree roots.