Don’t forget to water your trees to keep them healthy in the summer heat.
Hotter weather is on its way, with highs in the high 80s and even 90 degrees next week. Your trees will suffer in the summer heat without occasional deep watering. Don’t forget to water your trees in summer to keep them healthy.
You may think that the occasional rain we get in summer is enough to keep your trees healthy. But over the last several years, as our summers have gotten hotter and drier, we have seen signs of drought stress in our clients’ trees. Unfortunately, by the time a tree shows signs of stress, it may have been suffering for a few years.
Why to water your trees
It costs a lot to remove and replace a dead tree.
We understand that you may be reluctant to spend money to water your trees. But if your tree dies, you will need to spend a lot of money to have it removed, and more money to replace it. And you will have to wait many years for the new tree to have a large presence in your yard.
Trees have many benefits.
Trees are also important in our urban environment. They provide shade on hot days, provide shelter and food for wildlife, reduce stormwater runoff, help keep the water clean, clean the air of toxins . . . and they are a beautiful asset in your landscape.
Trees that are stressed have more pest problems.
When plants begin to have water stress issues, they often emit destress signals that many damaging insects pick up on. This is why one tree that is healthy and fine can be right next to a tree struggling, and the struggling tree is ravaged by pests.
Many of our pest problems are water associated. Outbreaks and infestations of aphids, spider mites and lace bugs are all directly related to whether the plant has the moisture it needs to survive and thrive.
Drought kills trees when the plant loses more water through its leaves or needles than it can replace from the soil with its root system. Without enough water, trees cannot make food by photosynthesis.
When this begins to happen, the tree will send out chemical signals to pests so the pests can come in and finish the job. In nature, the weak die and only the strong survive.
The easy answer is that we usually must water in our dry months, even if we think the trees are ok. They may look fine right now, but the following years is when the damage will show.
When to water your trees
The easiest way to know when your tree needs water is to check soil moisture. A soil probe allows you to measure how deeply the water has penetrated. This will let you know whether you are reaching deep enough into the root zone to encourage your plants to grow deep roots. If you don’t have a soil probe, you can use a long screwdriver, at least eight inches long.
Just poke the probe or screwdriver into the soil. It will pass easily into moist soil, but be difficult to push into dry soil. If you can’t poke it in at least six inches, it’s time to water. This technique works best in clay and loam soils.
Watch our short video “Watering 101: Create Strong and Healthy Plants.” It explains how and why to water deeply. Watering deeply is key to healthy plants. Start at 1:08 for instructions on how to use a soil probe.
How to water your trees
When you water your trees, shrubs or other plants, do it correctly. You need to maximize the water penetration in the soil and minimize the amount of evaporation. Evaporation wastes water; it cannot get into the soil and help the tree.
A tree’s roots are relatively shallow (three feet or less deep), and most roots are within 12 inches of the surface. Roots extend well past the canopy drip line. Illustration: University of Minnesota Extension.
Water the entire root zone area, and then let it partially dry out.
This may take a bit of thinking, because the active root zone for most plants is at the outer tips of the leaves and beyond. For many trees this can be a large area.
It will not help the tree if you water nearer the trunk. No root tips are there bringing in moisture for the plant. So make sure you water the entire root zone area of the plant.
Then allow the area to dry out partially. No roots want to be waterlogged all the time. The roots need oxygen. This happens when the soil is allowed to dry out some between waterings.
Water slowly and deeply for healthy plants.
You need to water long enough for the water to penetrate deep into the soil. Watering deeply encourages deep roots that help a tree resist drought stress. Tree roots may be as deep as 10 inches below the soil surface.
Your irrigation system probably doesn’t provide enough water to soak in deeply. It is better to use a soaker hose or drip line because it is sits directly on the soil surface and will water your tree slowly. It may take a few hours for the water to penetrate deep into the soil.
If your soil is already dry, it may take a few waterings to “soften” up the top of the soil layer, allowing water to penetrate deeper into the soil profile.
Soil is like a sponge. If a sponge is allowed to dry out completely, you cannot just pour water quickly onto its top. The water will run off and not penetrate at all. But if you slowly pour the water on the sponge and allow it to soften up the surface, then the additional water will freely percolate through the rest of the sponge.
Water when it is cool.
If you water in the heat of the day, most of the water will evaporate into the air before it has a chance to get to the soil. Mornings are the best time to water, with evening the second choice. Be aware that if you regularly water in the evening, it can promote some diseases.
Mulch is helpful.
A thick layer of mulch (at least a few inches) will help your tree retain water. It also keeps the soil cooler. To prevent rot, don’t pile mulch directly against the tree trunk; keep it at least a hand’s width away.
If your tree is in your lawn, mulch is also helpful to prevent the lawn from competing with the tree for water, nutrients and root space. According to University of Minnesota Extension, “Turf wins because its dense fibrous root system prevents woody plants from producing water-absorbing roots in the top few inches of soil. As a result, woody plants grow more slowly in turf areas than in mulched or bare soil areas.”
How to water newly planted trees
If you planted any trees this year, or within the last two years, a watering bag is a convenient way to water your trees slowly and deeply. Watch our video for details.
This is quite a good guide to protect & preserved our trees.
Conserve water by protecting our trees.
Very useful. Thanks.
You’re welcome. We’re glad you find it helpful.