Long, hot and dry spells are becoming a more familiar part of British summers. Lawns turn brown within days, but the effects on trees are slower and harder to spot. Drought stress can affect a tree’s health for several years after a dry summer, and on clay soils it can also affect nearby buildings.
How drought affects trees
Trees lose huge amounts of water through their leaves on hot days. When the soil dries out, the roots cannot keep up. To protect itself, a tree may close the pores in its leaves, stop growing, and in severe cases shed leaves or even whole branches.
Young trees planted in the last few years are the most at risk, because their roots have not yet spread far enough to find deeper water. Older trees are more resilient but can be weakened by repeated dry summers.
Signs of drought stress
- Leaves wilting, curling or turning brown at the edges
- Leaves turning yellow and falling early, sometimes in midsummer
- Thin, sparse crowns with smaller leaves than usual
- Dieback of twigs and branches at the top of the crown
- Cracks in the bark on young trees
Some of these signs may not appear until the following spring, when a stressed tree comes into leaf late or not at all on some branches.
Summer branch drop
On hot, still afternoons, large healthy looking branches occasionally drop from mature trees without warning. This is known as summer branch drop. It is not fully understood but is linked to heat and water stress. It is one reason to avoid sitting or parking directly under large, heavy limbs during a heatwave.
Clay soils, trees and subsidence
Clay soils shrink as they dry and swell again when they get wet. Parts of Worcestershire sit on clay, and in a dry summer, trees growing close to houses can draw enough moisture from the soil to make it shrink beneath shallow foundations. In some cases this can contribute to subsidence.
If you notice new cracks in walls, sticking doors or windows near a large tree, speak to your insurer and a structural surveyor before any tree work is carried out. Removing a large tree suddenly can sometimes cause the opposite problem, as the clay swells back up. Careful, staged management such as regular crown reductions is often the better approach.
How to help your trees in a dry spell
Water young trees properly
A thorough soak once or twice a week is far better than a light sprinkle every day. Aim the water at the root area, not the trunk. Watering bags or a slow running hose work well.
Mulch
A layer of woodchip or bark mulch around the base of a tree, kept a few centimetres away from the trunk, helps the soil hold moisture and keeps it cooler. Woodchip from tree work is ideal, as we explain in repurposing felled trees.
Avoid heavy pruning in a drought
Major reductions add stress to a tree that is already struggling. Unless there is a safety issue, heavy work is better left until autumn or winter. See our guide to summer tree pruning for what can be done in the warmer months.
Protect the roots
Avoid compacting the ground under trees with vehicles, storage or building work. Compacted soil holds less water and air, making drought stress worse.
After the drought
It is worth having mature trees checked after a very dry summer, especially those near homes, roads and gardens. Dead wood and weakened branches can be removed before the autumn storms arrive.
Faithful Tree Care offers tree inspections, crown reductions and deadwood removal across Worcester, Worcestershire and Herefordshire. Call 07828 786300 or send us an enquiry.
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