Urban Arborists

Seasonal Activities

We had cool and wet this spring, followed by a hot and dry start to summer. These are the sorts of conditions that favor summer branch drop, also called sudden limb drop. Otherwise healthy branches may fail, even when there is little wind or storm to cause the failure. No one is quite sure why it happens. One factor may be vigorous new growth that weighs down branch tips, followed by drying of branches tissues and weakening of wood.

There also appear to be more branch failures related to an increase in the number of convective storms. These storms – usually thunderstorms – are accompanied by winds with large updrafts and downdrafts. Branches may bend in unpredictable ways, leading to more and larger failures. .

In this climate, therefore, we are especially vigilant in our safety pruning. We reduce the weight of long, heavy limbs, where their failure might do harm or damage. If a branch is seriously wounded in a storm, we may remove it. We are on the look out for cracks and other signs that all is not well aloft. When older trees are heavily exposed to winds, we may reduce their crowns on the tops and/or sides.

We have also seen a variety of summer pest pressures this year. We have come to expect fall webworm on ailanthus and other city trees. Once a problem only every 5 years or so, it now troubles us 4 years out of 5. A surprise this year has been the large amount of cottony maple scale, particularly on the backs of the leaves of a large number of trees and shrubs.

Fortunately, both these pests are very treatable.