Is summer heat hurting your trees? The fix may be less water, not more

SALT LAKE CITY — In Utah's summer heat, gardeners may see their beloved trees start to struggle, with leaf scorch, iron chlorosis, and other symptoms.

Many Utahns may see their trees struggle and therefore use drastic and expensive measures to make sure their tree survives, but sometimes the best fix is the easiest one.

Often, Utah's trees flourish in springtime, then when July and August roll around, the trees look tired and their leaves may start to suffer. USU Extension horticulturist Taun Beddes says the main culprit is Utah's low humidity and intense summer sun: By late summer, trees can't always move water to their leaves fast enough, resulting in browning around the edges or in patches.

This episode of KSL Greenhouse aired on Sept. 5

It may be difficult not to stress when a tree begins to struggle, with misconceptions of tree diseases or borers top of mind. The good news is in most cases, as long as the tree was well established and correctly watered in the springtime, it is unlikely to be a disease affecting it.

The problem may be the very thing that is thought to help the tree: water.

Many Utahns see the high temperatures and dry conditions and think watering their trees more will help the tree, but doing so may be hindering its growth and survival. We need to start by looking at our soil.

Most plants like slightly acidic soils; however, Utah soil tends to be more alkaline. Many of the nutrients plants need in order to thrive are only water-soluble in acidic environments. This is why iron chlorosis can be more prevalent in Utah trees. The higher pH in our soil makes iron less soluble, so trees can't get the iron they need.

One way to help iron, manganese, and other vital minerals reach the roots and be absorbed into the tree is increased oxygen content in the soil. However, when trees are watered more often, it packs the soil, reducing oxygen and making it harder for trees to take up the iron and manganese they need.

That is why Beddes always preaches less frequent, but deeper tree irrigation. That means watering only 3-4 times per month to a depth of 18-24 inches, getting the water the tree needs, while still allowing for oxygen in the soil.

Mulching around the roots of the tree will also help the tree maintain water in its soil. See this episode of the KSL Greenhouse Show for more details on tree irrigation.

This archived episode of the KSL Greenhouse show aired on Jun 20

The best way to treat sun scorch on your tree is prevention. That is why this simple and more water-efficient irrigation technique is crucial in Utah summers.

Unfortunately, with hotter summers, sun scorch may be an inevitability for some trees, especially if they are in park strips or close to asphalt, concrete, or buildings that radiate heat. Norway maple, horse chestnut, linden, cottonwood, and willow are all trees more prone to summer heat issues. Trees with waxy and/or small to medium-sized leaves will have a better chance in the summer heat: Queen Elizabeth maple, zelkovas, oaks, etc.

Have questions about the symptoms you see in your trees? Call 801-575-8255 or text 57500 on Saturday mornings from 8-11 a.m. to reach the KSL Greenhouse show.

Related topics