Knowledge from Olle Garden Bed: How to Revive Plants from Heat Damage

Don't give up on your heat-damaged garden. Follow these steps to revive your plants. The following content also has some reference value for raised garden beds.

With rising temperatures and heatwaves suffocating areas in the summer, many plants may succumb to heat damage. The intense heat can scorch leaves, cause dehydration, and make indoor and outdoor plants more susceptible to pests and diseases. Wilt, yellowing, crispy tips, and leaf drop are common symptoms, especially during drought periods. While losing crops or plants due to heat damage can be devastating, try not to panic. There are several steps you can take to help your plants recover from heat damage and prevent such situations in the future.

 

When does heat damage occur?

Heat damage most commonly occurs in late spring and summer when sunlight is at its hottest. Both indoor and outdoor plants are affected by this. As the intensity of sunlight increases towards late spring, it can burn indoor plants that were thriving well in the same location during winter. Bringing indoor plants outdoors without acclimatizing them can also lead to heat damage. Popular and beautiful indoor plants like Calatheas, Dragon Trees, and Peace Lilies often get burned under intense direct light.

For outdoor plants, heat damage is most likely to occur when temperatures rise early in the season. Plants that haven't had a chance to produce enough foliage to provide shade are at the highest risk. Prolonged exposure to temperatures above 85 degrees Fahrenheit can result in heat damage, especially when nighttime temperatures are also high. Cold-season crops like lettuce, radishes, and cilantro are particularly prone to heat damage.

In addition to air temperature, high soil temperature can also harm plant roots. For example, spinach won't germinate in soil temperatures above 75 degrees Fahrenheit. Plants in black containers also heat up much faster than those in other colored pots and in-ground plants. While early summer may cause damage to cold-season crops, the heat of the soil towards the end of summer, when August is at its hottest, can even harm warm-season crops. The severity of heat damage depends on various factors, including plant size, temperature, humidity, and wind speed.

Materials Needed

It's not difficult to help plants recover from heat damage if you use the right equipment.

Garden fabric, shade cloth, or bedsheets

Ropes or zip ties

Garden hoops, PVC pipes, bamboo stakes (optional)

Shovel

Mulch

Step 1: Move the Plants

The first step in helping plants recover from heat damage is to move them out of direct sunlight. If possible, relocate the affected plants to a shady spot. For indoor plants, move them a few feet away from the window or use curtains to shield them from direct sunlight. Placing plants behind or below another plant can also provide sufficient coverage. Most importantly, ensure that the plants have shade during the midday when the sun is at its hottest.

For potted outdoor plants, lean them against a north-facing exterior wall or fence. Look around and get creative with the space you have available. If there are corners, shelves, umbrellas, or awnings that offer shade, these are ideal positions for potted plants.

Step 2: Cover the Plants

For plants that are difficult to move or rooted in the ground, try covering them with fabric. You can use garden fabric or shade cloth if available, but old bedsheets can also do the job. Secure the fabric to stakes, garden edging, or other protruding structures using ropes or zip ties, similar to how you would secure a tarp. To ensure proper airflow, the fabric should not be in direct contact with the plants.

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

Step 3: Mulch

Mulching also provides much-needed shade for the plant roots and helps retain moisture. For outdoor plants, spread a layer of mulch about 4 to 6 inches thick around the base of the plants. Straw, pine needles, and even tree leaves and grass clippings make excellent choices for mulch, along with traditional wood chips. Mulching also has the additional benefit of helping reduce weed growth.

Be cautious with mulching for indoor plants as excessive moisture can lead to root rot. An inch should be sufficient, typically only needed for plants that prefer more moisture, such as peace lilies, calatheas, and prayer plants.

Note: Mulching is best done in late spring.

Step 4: Wait

Try not to do too much at once. Unfortunately, you can't reverse the burn marks on the leaves, but your plants can bounce back. While wilted plants may look dreadful, wilting is a water-conserving defense mechanism for plants. Let your plants acclimate to the new environment. If it's still scorching during the day, wait until the sun has set before watering. This will help conserve water and ensure that your plants utilize water resources effectively. Evaporation happens quickly under high temperatures, meaning your plants absorb less moisture.

Even though wilted and yellowing leaves may bother you, hold off on pruning until later. These leaves still provide protection and energy for the rest of the plant. Instead of pruning, let the plant shed the leaves on its own. Once the heatwave passes and temperatures return to normal, you can resume your usual pruning routine.

Avoid fertilizing during the heatwave. Nitrogen in fertilizers promotes new leaf growth rather than protecting the plant's current leaves and root system.

Step 5: Watering

If your plants are experiencing heat stress, they may also be lacking water. However, this is not always the case, and wilting can also be a sign of overwatering. This is another reason why you want to wait until the sun has set before considering watering. If your plants don't need water, the wilted leaves should recover once the day's heat has passed. If your plant's leaves remain wilted and the soil is dry, it's time to water.

Water deeply and slowly rather than just wetting the soil surface. While watering in the evening may also be necessary during a heatwave, thoroughly water in the cool morning. This will help ensure your garden has sufficient moisture to withstand the intense afternoon sun.

For potted plants where water loss is rapid, consider using saucers underneath them to maintain moisture throughout the day. Drip irrigation systems can also help with slow and steady watering, ranging from simple DIY plastic bottle contraptions to more elaborate underground systems.

Note: Windy conditions, especially when combined with a heatwave, increase the water demand.

Step 6: Care

For fruiting plants, harvesting fruits, even partially ripe ones, is another way to help plants conserve energy and survive the heatwave. Water deeply according to the specific needs of the plant when the soil is dry. Wait for yellowing or wilted leaves to drop off.

Once the plant starts to recover, it will begin pushing new growth, and you can cut off any remaining damaged leaves or fruits. The sooner you take action, the faster your plant will recover. If it's a fruiting plant, growth may be temporarily stunted, but if you're lucky, new fruits will grow to full size.

Step 7: Prevention

Keep a close eye on the weather in your area and prepare before the heatwave takes a toll on your garden and plants. Covering, shading, and deep watering the plants before the high temperatures hit are the best ways to prevent heat damage. Duringthe early season, plan your garden carefully to ensure that shade-loving crops are not exposed to excessive sunlight.

 

For cold-season and long-season crops like pumpkins, brussels sprouts, and cauliflower, start them early in the season, whether in a greenhouse or indoors. This will give them a head start in the garden and time to develop foliage that provides crucial shade. Alternatively, depending on your climate, consider planting cool-season crops in the fall. Also, choose seeds and plants that are well-suited and drought-tolerant for your region when purchasing.

 

Adapting to a New Environment

If you're trying to bring indoor plants outdoors during a heatwave, you may still want to relocate the plants. When moving plants to a new location, especially one with higher light intensity, it's best to do it gradually. This is especially important for plants with medium to low light requirements.

Move the plants to the preferred location for a few hours each day, gradually increasing the time. Start in the early morning, ensuring that the plants have shade during the hottest part of the day.

Heatwave? No problem!

While crispy and brown leaves won't turn green again, don't give up on heat-damaged plants or your garden. Many plants will bounce back and thrive with a little extra care. The wilted leaves will drop off, and once the recovery occurs, your plants will reward you with new growth.