As temperatures soar and heatwaves smother regions in the summer months, many plants can succumb to heat damage. Hot temperatures can burn the foliage, dehydrate, and even make indoor and outdoor plants more susceptible to disease and pests. Wilting, yellowing, brittle tips, and leaf loss are common symptoms, especially in combination with periods of drought. While it can be devastating to lose a crop or plant to heat damage, try not to panic. There are several steps you can take to both revive your plants from heat damage and prevent it from happening in the future.

When Does Heat Damage Occur?

Heat damage most often occurs in late spring and summer when the rays of the sun are the hottest. This is the case for both indoor and outdoor plants. As the intensity of light increases in late spring, the sun’s rays can burn houseplants that were fine in the same location during the winter months. Bringing indoor plants outside without acclimatizing them first can also cause heat damage. Calatheas, dracaenas, and peace lilies, for example, are popular and beautiful houseplants that often burn in intense direct light.

For outdoor plants, heat damage most often occurs when temperatures rise early in the season. Plants that haven’t had the chance to send out enough leaves to provide shade are most at risk. Prolonged temperatures above 85 degrees Fahrenheit can lead to heat damage, especially if nighttime temperatures are also high. Cool-season crops, such as lettuce, radishes, and brassicas, are particularly prone to heat damage.

In addition to air temperatures, high soil temperatures can also damage plant roots. Spinach, for example, cannot germinate in soil temperatures above 75 degrees Fahrenheit. Plants in black containers also heat up substantially faster than other colored pots and in-ground plants. And while early summer may take a toll on your cool-season crops, the heat of the late-summer soil, when it's at its hottest in late August, can damage even the warm-season crops. The level of heat damage depends on many factors, including the plant size, temperature, humidity, and wind speed.

Materials Needed

wheelbarrow and shovel
Image credit: mariya_m via Pixabay

Reviving plants from heat damage isn't difficult with the right equipment.

  • Garden fabric, shade netting, or bedsheets
  • Rope or zip ties
  • Garden hoops, PVC piping, bamboo sticks (optional)
  • Shovel
  • Mulch

Step One: Move Plants

Potted lush plants on cart in garden

The first step is reviving plants from heat damage is to move them out of the direct sun. If possible, relocate the affected plants to a shaded location. For indoor plants, move them back a few feet from the window, or pull a curtain across the window to protect them from the sun. Placing the plant behind or under another plant may also allow for adequate cover. Most importantly, ensure plants have shade midday, as this is when the sun is hottest.

Tuck outdoor pots up against a north-facing exterior wall or fence. Look around and be creative with the space you have. If there are nooks, ledges, umbrellas, or awnings that provide shade, these are perfect locations for your potted plants.

Step Two: Cover Plants

Plants in a row house

For plants that are difficult to move or those rooted in the ground, try covering them with fabric. You can use garden fabric or shade netting if you have it, but old bedsheets also do the trick. Secure the fabric to bamboo sticks, garden edges, or other raised structures, with ropes or zip ties like you would a tarp. To ensure proper airflow, the sheet shouldn’t touch the plant.

For something more permanent, you can install garden hoops or PVC piping to hold the cover-up. Row covers have many benefits, including protecting plants from pests and wind.

Step Three: Mulch

Hands on a pile of mulch

Mulch can also provide much-needed shade for plant roots and help retain moisture. For outdoor plants, spread mulch 4 to 6 inches thick around the base of your plants. Straw, pine needles, and even leaf and grass clippings are all great options for mulch, along with traditional wood chips. Mulching also has the added benefit of helping to cut down on the weeds.

Use mulch sparingly for indoor plants, as too much moisture can lead to root rot. An inch should be sufficient, and is often only necessary for moisture-loving plants, such as alocasias, calatheas, and crotons.

Mulching is best completed in late spring.

Step Four: Wait

Try to avoid doing too much at once. Unfortunately, there’s nothing you can do to reverse burn marks on the leaves, but your plants can bounce back. While wilted plants can look scary, wilting is the plant’s defense mechanism to conserve water. Let your plants acclimatize to their new environment. If it is still the heat of the day, wait until the sun has set before watering. This will help to conserve water and ensure your plants use the water efficiently. Evaporation happens quickly in hot temperatures, meaning your plants absorb less of the water.

Even if the wilting and yellowing leaving are bothering you, leave pruning for later. These leaves are still providing protection and energy for the rest of the plant. Instead of pruning, let the plant drop the leaves on its own. Once the heatwave passes and temperatures return to normal, you can resume your usual pruning routine.

Do not fertilize during a heatwave. The nitrogen in the fertilizer encourages new leaf growth instead of protecting its current leaves and root system.

Step Five: Water

If your plants are heat stressed, they may also be lacking water. This is not always the case, and wilting can also be a sign of overwatering. This is another reason you want to wait until the sun sets before considering water. If your plants don’t need water, the wilted leaves should recover once the heat of the day has passed. If the leaves of your plants are still wilted, and the soil is dry, now is time to water.

Water deeply and slowly as opposed to giving the soil light sprinkles. While watering in the evenings may also be necessary during a heatwave, do a thorough watering in the morning before the heat of the day. This will help to ensure your garden is well-hydrated for the hot afternoon sun.

For potted plants losing moisture too quickly, consider using saucers underneath them to hold water throughout the day. Drip irrigation systems can also help provide water slowly, and can range from simple DIY plastic water bottle contraptions to more elaborate underground systems.

Windy conditions, especially in combination with heatwaves, can increase water requirements.

Step Six: Care

For fruit-bearing plants, harvesting the fruit, even partially-ripened fruit, is another way to help your plants conserve energy and survive the heatwave. Water deeply when the soil is dry according to the plant’s particular needs. Wait for the yellowed or wilted leaves to fall off.

Once the plant recovers, it will start pushing out new growth, and you can cut off any remaining damaged foliage or fruit. The sooner you act, the quicker your plants will recover. If it was a fruit-bearing plant, the growth may be temporarily stunted, but with any luck, the new fruit will grow to full size.

Step Seven: PreventCrouching man volunteering in a Garden

Keep an eye on the weather in your region, and prepare for the heatwaves before they take out your garden and plants. Covering, mulching, and deep watering your plants before the high temperatures hit is the best way to prevent heat damage. Early in the season, carefully plot out your garden to ensure your shade-loving crops are not in full sun.

For cool-season and long-season crops, such as squashes, brussels, and cauliflower, start these early in the season, either in a greenhouse or indoors. This will give them a head-start in the garden, and time to push out leaves that provide vital protection from the sun. Or, depending on your climate, consider growing your cool-season crops in the fall instead. In addition, when sourcing seeds and plants, select ones that grow best in your region and are drought-resistant.

Acclimatizing to a New Environment

Potted plants in patio of apartment house

If you were trying to bring an indoor plant outside when the heat damage occurred, you might still want to relocate the plant. When moving a plant to a new location, especially one with higher light, it’s best to do this gradually. This is especially important for plants that have medium to low light needs.

Move the plant to the preferred location for a few hours daily, slowly increasing the time. Start with the early morning hours and ensure the plant has shade during the heat of the day.

Heatwave? No Problem!

While crispy and brown leaves won’t turn green again, don’t give up on your heat-damaged plants or garden. Many plants will bounce back thriving, with a little extra care. Dead foliage will drop, and once recovered, your plants will reward you with new growth again.

Have you ever revived a plant with heat damage? Share your experience in the comments.