Why Are There Yellow Leaves on Trees in Summer?

Rich, green leaves are a staple of summer. They are a crisp, bright and pleasant addition to every landscape. Plus, we love their shady canopy on sunny days.

If you happen to spot yellowing leaves on your trees, you want them to return to their green glory. An Ontario-based reader recently had a similar goal. She asked us why her river birch leaves were turning yellow and falling off – and how she could fix it.

There are many reasons why you too could see these symptoms. Run down the checklist below to help diagnose your tree.

Test 1: Test for dry soil

If trees aren’t hydrated, the leaves can turn yellow as they try to conserve water.

Test your tree’s moisture by sticking a screwdriver into the soil. If it’s hard to push in, chances are the tree is thirsty and could use a deep watering.

Test 2: Check soil moisture

If the screwdriver test proves there’s moisture deep into the roots, water less.

Your reflex might be to water at the sight of suffering leaves, but overwatering can also lead to yellowing and leaf drop.

Test 3: Inspect and treat

Yellowing leaves and premature leaf drop may point to a leaf disease or summer pest infestation. Consider a free tree inspection to identify the pest or disease and the best treatment.

If an infestation is ruled out, the checkup may reveal a deficiency called chlorosis, which strips leaves of the chlorophyll needed to keep them green.

Begin by performing a soil test and adding any necessary soil amendments. Fertilizer also replenishes lacking nutrients, which in turn helps your tree. Remember, these actions need to happen on a regular basis to have a lasting impact.

Why, specifically, is my birch or river birch getting yellow leaves in summer?

If you, too, are seeing yellow leaves on your birch tree, there could be a couple reasons why.

Run through this checklist just for birch trees to find out what the problem is:

• Are there spots on those yellow birch leaves? If so, the problem is likely a leaf disease.
• Do you see something sticky on the bottom of the leaves? If so, it’s probably an insect.
• How much are you watering? As their name implies, river birches love to drink water. In the summer, when the water is limited, they’ll drop leaves if they get thirsty enough. To remedy, deeply water your birch tree each week, and add mulch to conserve moisture.
• How hot is it? If it gets too hot for too long, these trees drop leaves to conserve energy. This happens most often to newly planted trees. They toughen up a bit as they mature because their root system becomes better established.
• Didn’t see any of the above? Check the soil to see if there’s enough iron (or if the soil has too much pH). Remedy the problem with soil amendments or treatments.

Questions about your tree’s appearance? We’re here to help!