Heat Stress in Plants: How to Care for and Protect Plants from Sun Damage

By Linda Ly

What Causes Heat Stress in Plants

When temperatures start creeping above 85 degrees, you’re not the only one who’s stressed. Most plants suffer when the weather turns hot enough for a certain period of time. It causes irreversible damage by way of plant function or development. This isn’t merely droopy leaves in the heat of the afternoon; it’s things like stunted growth, leaf drop, leaf scald, failure to flower, or failure to produce seeds.

Heat stress can occur from high daytime temperatures, high nighttime temperatures, or high soil temperatures, and is the collective result of the intensity of the heat, the duration of exposure, and the rate of increase in temperature.

How to Protect Plants from Sun Damage

Did you know your plants can actually get a sunburn? The burnt foliage becomes tan or white, making the plants more susceptible to pests and diseases. Since the sun is harshest from midday to early afternoon, the best course of action is to provide shade for your plants during this period.

There are several ways to accomplish this:

• Put heat-sensitive plants in garden beds that receive afternoon shade from structures like a house, a shed, or a tall fence.
• Plant in garden beds that receive dappled afternoon light, such as those near trees or pergolas.
• Erect a shade sail, tarp, or other cover (fully opaque, semi-transparent, or mesh, depending on your needs) over your plants. In a pinch, even a lightweight bed sheet will work.
• Plant shorter, heat-sensitive crops like salad greens in the shade of taller, heat-loving crops like climbing squash, pole beans, corn, and okra. As the sun moves across the sky, the taller plants should cast cooling shadows over the shorter plants.
• If plants are in containers, move them under a covered porch or into a shaded area in the afternoon.

How to Care For Plants in Hot Weather

To help your plants survive a heat wave, remember to keep them consistently moist. In the summer, they may need twice as much water so make sure to adjust your programmable timer accordingly, or set a reminder to water with a hose more frequently. Most plants should be watered when the first 2 inches of soil feels dry. Container plants tend to dry out quicker than in-ground plants, so check them throughout the day to ensure they’re properly hydrated.

Mulch is crucial in hot climates as it helps conserve moisture in the soil and protects the roots from extreme soil temperatures. Apply a 2- to 3-inch-thick layer around your plants and water with Gilmour’s Thumb Control Watering Nozzle at the root zone in the early morning or late afternoon to reduce runoff and evaporation.