How to Evaluate a Garden’s Mature Trees and Shrubs
One designer’s checklist
Trees and shrubs are often called the bones of a garden. That’s why it’s important to choose their sites very carefully before planting them. Remember to consider their size and shape at maturity and how these details will fit among hardscape features and buildings. Don’t forget to look up! Are there utility wires or overhangs that your tree will reach as it continues to grow? If so, choose a different spot for that tree, and a different plant for this spot.
Of course, sometimes we’re gardening in a landscape where plants have indeed outgrown their designated space, whether it was the wrong spot to begin with, the plant grew more than expected or hardscape elements were added later. In such cases, perennial flowers and ornamental grasses can be easy to dig up and move. For their own health, mature trees and shrubs are usually best left in place, with changes made to their surroundings to accommodate them. If such adjustments are not possible, the tree or shrub likely needs to be removed entirely, though in some cases a professional may be able to reshape it to fit.
When deciding what to do about trees and shrubs in a maturing landscape, I evaluate them based upon a few key criteria:
Type: Invasive species, such as Norway maple, burning bush or Japanese barberry should be slated for removal. Native species or unique specimens should be identified and promoted.
Size: Overgrown trees should be considered for pruning or removal by a licensed arborist. (This is not a green light to fell a 100-year-old oak to provide sun for tomatoes!)
Health: A distressed or diseased tree poses a potential threat to people and property. Dead limbs should be pruned. If more then 30 percent of the plant is dead, take it down before it fails. Exceptions might be made for snags (dead trees) that stand well away from structures and paths, as these are a resource to birds and other wildlife.
Form: Neglected trees and shrubs that are ill-formed can be rejuvenated. Identify species that respond well to rejuvenation pruning, like lilac or ornamental pears, and prune them. Conifers like juniper and spruce often can’t be fixed. It’s better to remove and replace such eyesores.
Appropriateness to the site: Any garden plant must match the climate, soil and sun exposure its site offers. (These elements can change over time—especially the amount of sunlight, as nearby trees grow to cast more shade or new buildings appear—so it’s important to assess appropriateness every few years.) Ill-suited and disease- or pest-prone species should be swapped out for sturdy local natives.
