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'Tis the Season for Summer Drought

Posted on Wednesday, August 3, 2016

After a very dry spring and summer you may be noticing symptoms of drought in your trees:

- Yellowing and/or wilted leaves (like the River Birch, Betula nigra, pictured below)
- Smaller leaf size towards the ends of branches
- Leaves turning colour and falling too early
- Dead spots on leaves

Picture of yellowing leaf

Why do trees experience drought stress?

Water helps trees maintain their structure. Trees are like giant straws - water evaporates from the leaves, pulling columns of water up through the living wood from the roots. If there is not enough water in the soil, the cells that carry the water will collapse and water will no longer reach the top of the tree and tips of the furthest branches. This is why the leaves at these locations wilt and die.

Dissolved nutrients are also transported in water from the roots to other areas of the tree, so if water cannot get to the places where it is needed, neither will nutrients, slowing down growth and potentially causing parts of the tree to die back.

Diagram of transpiration

Three things that you can do to prevent drought stress:

1. Water your trees slowly and deeply, preferably with a soaker hose or Treegator™ bag, to make sure that water percolates down through the root zone, about 12-18 inches (30-45cm) below the surface of the soil. If you choose to water with a non-soaker hose or sprinkler, water in the evening!

Photograph of soaker hose setup

Photograph of Treegator bag setup

2. Mulch your tree in the spring, making sure that the mulch is only 3-4 inches (8-10cm) deep, and that it is kept away from the trunk (think “donut”, not volcano”). The point of mulching is to prevent water from evaporating from the soil into the air, but the reverse is also true, so don’t mulch during a drought!

Diagram of how to mulch

3. When planting, choose trees that are appropriate to your site’s moisture conditions. Look for ideas in this City of Toronto info sheet

What can I do if my trees are already suffering from drought?

Prune: It is very important to have dead branches pruned out of the tree if they are a hazard to people, animals or objects that may be underneath. It is recommended to leave as much of the live branches on as possible, though, at least until the tree is less stressed.

Water: It is never too late to begin watering properly. It may not save the damaged branches and foliage but it will help the tree recover and produce healthy new growth.

Services that we offer

Here are some services that may help you with your drought-stressed trees this season:

- Pruning
- Tree and shrub fertilization
- Shrub pruning
- Tree removal

Call for a free assessment and estimate: (905) 872-9103

References

Tree Responses to Drought
Proper Watering Techniques
Tree Care (LEAF)
"Do's and Don'ts" of Tree Care

Pics

Yellowing birch leaf
Transpiration diagram
Soaker hose watering technique
Gator bag watering technique
Mulching technique

Written By: Anna Mernieks July 22, 2016

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