Helping Our Trees Survive Extreme Heat

As I write this, much of the country is enduring another stretch of extreme summer heat. Day after day of high temperatures, intense sunshine and very little rainfall can be exhausting for us—but imagine what it's like for our trees.

Unlike people, trees can't move into the shade, turn on a sprinkler or pour themselves a glass of water. Once they're rooted in the ground, they rely entirely on the moisture stored in the soil and whatever rain Mother Nature decides to provide. During prolonged heat waves, that simply isn't enough.

At TreeHelp.com, one of the most common questions we receive during hot weather is, "What can I do to help my tree?" The good news is that there are several simple steps that can make a tremendous difference. The challenge is knowing what actually helps—and what can unintentionally make matters worse.

The first thing to understand is that heat alone isn't usually what damages trees. It's heat combined with drought. As soil dries out, tree roots struggle to absorb enough water to support the canopy above. To conserve moisture, trees begin shutting down normal functions, slowing growth and sacrificing leaves in an effort to survive.

Many homeowners panic when they see leaves beginning to curl, wilt or turn brown during a heat wave. While those symptoms certainly shouldn't be ignored, they're often signs of water stress rather than disease.

Some of the first symptoms you'll notice include leaves drooping during the afternoon, scorched or crispy leaf edges, yellowing foliage, premature leaf drop and a thinner-looking canopy. In severe cases, smaller branches may begin to die back as the tree directs its limited resources toward preserving its main structure.

These symptoms don't always appear immediately. In fact, it's very common for trees to look reasonably healthy during a heat wave and only begin showing stress several weeks later. That's why it's important to continue monitoring your trees long after temperatures return to normal.

Pay particular attention to newly planted trees. A tree planted within the last three years has a relatively small root system and is far more vulnerable than an established tree that has spent decades developing extensive roots. Young trees often require supplemental watering throughout prolonged hot weather.

One of the biggest mistakes I see homeowners make is giving trees a quick spray with the garden hose every evening.

Unfortunately, that doesn't accomplish very much.

Most tree roots responsible for absorbing water are found well below the soil surface. A brief watering wets only the top inch or two of soil, encouraging shallow roots while leaving deeper roots dry.

Instead, trees benefit from slow, deep watering.

Allow a hose to trickle slowly at the base of the tree for an extended period, giving water time to soak deeply into the root zone. Depending on the size of the tree and your soil type, this may take anywhere from 30 minutes to several hours. A slow soak is always more beneficial than frequent shallow watering.

It's also better to water deeply once or twice a week than to sprinkle lightly every day. Deep watering encourages roots to grow downward where moisture remains available longer. Timing also matters.

Whenever possible, water early in the morning. Cooler temperatures reduce evaporation, allowing more water to penetrate the soil before the day's heat arrives. Evening watering is also acceptable if morning isn't practical, but try to avoid watering during the hottest part of the afternoon when much of the moisture is lost to evaporation.

One product we've seen make a remarkable difference during drought conditions is Hydretain®, available through TreeHelp.com.

Hydretain isn't a fertilizer and it isn't a wetting agent. Instead, it helps plants capture moisture that already exists in the soil by attracting water vapour and making it available to plant roots. In many situations, it can significantly reduce watering requirements while helping trees better withstand periods of heat and drought.

While no product can replace rainfall or proper watering practices, Hydretain can become an excellent tool for homeowners trying to conserve water while still maintaining healthy trees.

Mulch is another simple practice that pays enormous dividends during hot weather.

Applying two to four inches of organic mulch around the base of the tree helps moderate soil temperatures, reduces evaporation and suppresses weeds that compete for valuable moisture.

One important point: keep mulch several inches away from the trunk itself. Volcano-shaped mulch piled against the bark traps moisture, encourages decay and can invite insects and disease. Think "doughnut," not "volcano." The mulch should form a wide ring around the tree, not a mound against the trunk.

Extreme heat is also not the time to prune healthy trees.

Pruning stimulates new growth, and tender new shoots require additional water at exactly the time when water is already in short supply. Every leaf on the tree is also helping produce energy through photosynthesis. Removing healthy branches during a drought reduces the tree's ability to generate the carbohydrates it needs to recover.

The only exception would be removing broken, hazardous or storm-damaged branches that present an immediate safety concern.

Likewise, avoid fertilizing trees during periods of severe heat stress and always avoid fertilizers with high or rapid release nitrogen.

Fertilizers encourage growth, and growth requires water. Wait until the tree has recovered and environmental conditions improve before applying fertilizer. If your tree would benefit from nutritional support later in the season, TreeHelp.com offers a wide range of specially formulated tree fertilizers designed to provide balanced nutrition at the appropriate time for over 60 different types of trees.

Heat-stressed trees are also more vulnerable to insects and diseases.

A healthy tree can often defend itself against many pests, but drought weakens those natural defence systems. Keep an eye out for unusual holes in the bark, sawdust-like material at the base of the trunk, increased insect activity, oozing sap, fungal growth or branches that fail to leaf out after the rest of the canopy has recovered.

Early detection often makes the difference between saving a tree and losing one.

Finally, remember that recovery takes time.

Many trees won't bounce back immediately after a heat wave ends. Some may continue shedding damaged leaves for weeks while gradually producing new growth the following season. Patience, proper watering and ongoing observation are usually the best approach.

Our trees are remarkable living organisms. Some of the maples, oaks and pines growing in our communities today have already survived decades of storms, droughts and harsh winters. Given the right care, they'll continue providing shade, cleaner air, wildlife habitat and beauty for generations to come.

As homeowners, we can't control the weather. We can't make it rain, lower the temperature or stop a heat wave. But we can help our trees weather these increasingly common periods of extreme heat by watering wisely, protecting the soil, avoiding unnecessary stress and recognizing the early warning signs before lasting damage occurs.

The care we provide today will determine how well our trees recover tomorrow. And that's an investment that benefits not only our landscapes, but everyone who enjoys the beauty and environmental benefits that healthy trees provide.

By Paul Oliver, Founder, TreeHelp.com