How to assess tree health and decide if one needs to come down

Published: September 9, 2020

Seasonal pruning trees with pruning shears. Gardener pruning fruit trees with pruning shears. Taking care of garden. Cutting tree branch. Photo by BigTunaOnline/Shutterstock

After a bad storm passes, you notice that your favourite old tree has lost a few limbs. You look warily at your cottage sitting beside it. Maybe it has to go. Is it time to yell timber?

“Removal is the last resort,” says Tobias Effinger, an arborist and the owner of Arboreal Tree Care in southern Georgian Bay. If the tree stands alone, away from buildings or footpaths, let it fall where it may—it will make a great home for wildlife. For a tree near the cottage, it’s better to prune it or even brace the tree with rods or cables before taking it down. Before you decide, run some diagnostics. “You’re looking at mainly the health and structure,” Effinger says.

To assess the tree’s health, start by examining its small, new shoots. Trees produce new growth through their twigs, marking each year with a ringed scar around the branch where development begins. If the gap between rings is increasing each year, the tree is in decline. If the gap has been steadily increasing in size, pruning a few weak branches to prevent damage to buildings before the next storm could do the trick.

Next, look at the tree’s foliage. Yellowing leaves in the spring or summer often point to a pH imbalance in the soil, which is easy to remedy, but they can also point to something trickier to fix, such as soil with a high buffering capacity. This means that the soil isn’t absorbing enough nutrients to adequately feed the tree’s roots. If the soil is too clay-like, the tree can get waterlogged and start to rot. If that happens, it might be time for it to come down.

Finally, check the structure of the tree. Examine the trunk for decay—deep cracks, soft spongy wood, or evidence of carpenter ants (look for sawdust at the base of the tree). You won’t fix those problems by pruning, though it’s possible that an arborist could brace the tree rather than remove it. Work up from the base, inspecting the unions where the trunk splits into limbs for “bark inclusions,” rough spots that indicate the tree’s limbs are cramped and don’t have enough room for stable growth. Next, look out for broken branches or cracks where branches attach to the trunk, removing any that won’t hold through heavy weather. Pruning a tree to keep it alive is a multi-stage process that might span several years. “The tree reacts to everything we do to it,” says Effinger. “Waiting for the tree to respond to our care is part of the plan.”

Pro tip
Pruning unhealthy branches increases air flow and sunlight to the healthy parts.

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