5 Garden-Saving Tips for Protecting Your Plants During a Heat Wave

Heat waves are sweeping across the country this summer, wreaking havoc on just about everything under the sun, causing heatstroke, wildfires, drought, and overall devastating impacts. While it's important to take health and climate risks posed by extreme heat seriously, the smaller-scale impacts shouldn't be overlooked either. 

Take your outdoor garden—though saving your plants might not feel as pressing, if you've spent time and effort curating and caring for a large spread of outdoor plants, that shouldn’t go to waste. If your garden looks more wilted each time temperatures climb, don’t give up just yet. Here's what master gardeners from especially heat-prone states recommend when it comes to caring for an outdoor garden in extreme conditions, plus how to tell which plants need extra special care.

Tips to Help Your Plants During a Heat Wave

Use one (or all) of these expert-recommended tips to save your garden from scorching summer temperatures.

1. Mulch in Moderation

Jayla Fry, a program coordinator for the Texas Master Gardener program, says mulching is one of the best ways to get ahead of the adverse effects of a heat wave. This simple and affordable fix isn't only nice to look at, but it can make your plants more resilient by decreasing weeds that compete for moisture and slowly evaporation.

“Weeds will take moisture out of the soil and away from the plants that you want," Fry says. "Mulch will help decrease the weeds and evaporation from the soil, and it’ll help moderate the soil temperature. So, I can’t stress mulching enough."

2. Water Correctly

It's fairly obvious that you’ll need to water your plants during a heat wave, but it’s not as straightforward as you may think. There are some important precautions to keep in mind to avoid wasting water during a drought-prone period and to ensure your plants are getting watered the right way.

According to Michael Chamberland, an urban horticulture expert who works with the Maricopa County Master Gardener program in Arizona, most people water their plants too often, and they don’t supply enough water each time they do. Trees and other larger plants need a significant soak so that the water reaches their large root systems. 

“They apply a little bit of water every day,” Chamberland says. “That can be good for vegetables and flowers and small plants, but that really creates problems with trees and other larger plants.”

Watering your plants every day (or more frequently than they need to be) can be damaging because it doesn’t give the soil enough time to dry before the next soak session. Soil that never dries is prone to increased mold and rot. Plus, depending on your soil type, never letting the soil dry out can fill air spaces between soil particles with water, depriving the roots of your plants of oxygen, a vital part of their photosynthetic diet.

When the temperature is high, it's especially important to keep your plants well hydrated. However, it's best to give your plants a deep soaking every few days rather than a daily splash.

3. Try a New Irrigation System

Though the concept of irrigation may sound intimidating, using an irrigation system doesn’t necessarily mean embarking on an expensive or extensive garden renovation. Fry suggests following a cycle-and-soak pattern, watering in short, 15-minute-long intervals with breaks in between, to reduce runoff and allow water to soak down into the soil. Cycle-and-soak irrigation can be done by hand or integrated into a landscape’s design with more technical irrigation systems.

“[If you] really allow that moisture to drop deep into the soil, the roots of the plant will search for that moisture,” Fry says. “If you’re just watering the very top layer of your soil, that's where your roots are going to stay, and so it doesn't have as great a capacity to pull from the moisture. You train your plants, essentially, to seek out the moisture.”

Fry also recommends watering your garden via drip irrigation. This can look as simple as a soaker hose placed in vegetable or flower beds, or a DIY version using kits you can purchase online. This method not only conserves water, but it also takes care of any over or under-watering concerns you may have. Plus, the systems can be rigged to run automatically, so you don’t have to run back and forth to turn on the hose.

4. Plant at the Right Time

An easy way to prevent heat damage is to avoid planting any new greenery during a heat wave (or during the hottest months of the year, unless you live somewhere fairly mild). Starting the plants off in a stressful environment won’t set them up for success.

“At that time of the year, it’s stressful on a plant to be planted,” Chamberland says. “They're going, usually, from a pot into the soil, so the root environment is changing.”

It's always preferable to wait for milder temperatures in spring and fall to do your planting. This gives your new plant time to develop more roots that can help it weather heat and cold better.

5. Try Shading

If mulching and irrigation aren't doing enough, it might be time to look into plant coverings. Horticultural shade cloth is the technical term, but just about any kind of cover will do—Chamberland says you can even use window screens.

He suggests finding netting that allows around 70% of the sunlight in (usually marketed as offering 30% shading). Floating row covers also can work. Focus on shading especially sensitive plants that need a bit of extra care during the worst of heat waves.

Keep in mind that too much shade can be a bad thing, too—your plants might burn when re-exposed to full sunlight if you cover them all summer. Move your potted plants to shadier areas (even inside will do) when the heat hits. Even if they normally need full sunlight, this will give them the chance to cool down.

How to Know If Your Plant Needs Extra Help

It’s clear that hotter-than-average temperatures aren’t great for your garden, but what signs of stress should you look out for when a heat wave hits? The short answer is that it depends on the plant. Some may start wilting quickly, making it easy to tell when to break out the hose, but others might not appear to be damaged until it’s nearly too late.

“It really depends on the different plants—plants show things differently,” Fry says. “One telltale sign that a lawn is suffering is that you can walk across your lawn and you can see the steps where you have been. But some plants are different, and they may not show it until all of a sudden they drop their leaves.”

Some common signs of damage include dulling, wilting, and leaves beginning to curl or roll, but Fry says that it’s important to observe your plants closely because it becomes easier to tell when to intervene as you gain more gardening experience. In the meantime, the solution to this predictability problem is to check your soil’s moisture.

“My predecessor used to always say we all have moisture meters—stick your finger down in the soil and feel,” Fry says.

You’ll want to make sure that the soil surrounding your plants is damp, all the way past the roots. If you’re not the biggest fan of dirt under your nails, Chamberland has another option to fall back on: a soil probe. This simple tool, a usually 3-foot-long metal rod, can be pushed into the ground to scope out how far down the moisture goes.