Cultivating a summer garden is the best way to brighten up your backyard for all those outdoor BBQs, patio dinners, and porch hangouts. But when temperatures soar and rain is nowhere in the forecast, many warm-season vegetables and warm-weather flowers undergo severe stress that can undermine their health and sabotage your gardening efforts. According to Florence Smith, horticulturist at the Missouri Botanical Garden, during a heatwave, plants enter a semi-dormant state to conserve their energy and lose moisture at a rapid rate, leading to deterioration. “Plants may begin looking more ragged with wilted or curling leaves, and they may drop flowers and fruit, slowing their overall production,” Smith explains.
While you can’t control the weather, you can give your plants the tools they need to combat the extreme temperatures. With precautionary measures like watering deeply and offering shade, you can protect your plants from the decline that naturally happens in the face of intense heat. To prevent your garden from needlessly suffering, we asked Smith and Longwood Gardens horticulturist Renee Watson to reveal their best-kept tips and tricks to help your plants survive summer heatwaves.
Aim for Deep Watering
When a heatwave hits, thoroughly hydrating your plants is one of the most important ways to replenish them. Keep in mind that your watering technique and frequency can make or break your results: Instead of lightly spraying the surface on a daily basis, deeply soak the soil whenever it’s dry. “Watering for too little time may simply saturate only the surface of the soil (which still leaves the plants thirsty), rather than down to the root level,” Smith notes. To deeply penetrate the root systems while preventing fungal diseases, Watson recommends aiming the hose at the base of the plant, not the leaves.
Provide Moisture in the Morning
Just like the amount of water matters, so does the time of day. In the midst of sweltering conditions, early morning is the best time to hydrate your plants, according to both experts. “Since morning temperatures are cooler and the sunlight is less intense, more water is likely to be absorbed by the soil instead of evaporating into the heat of the day,” Watson says. “A good, thorough water in the morning also gives the plant ample time to soak up the water into its roots and prepare for the hot day ahead.”
Apply a Layer of Mulch
To protect your plants from unbearable heat, apply a fresh layer of organic mulch, shredded leaves, clean straw, or grass clippings. Because mulch acts as an insulator, it keeps roots cool and locks in moisture, which is especially needed during dry spells and heatwaves. Not to mention, mulching suppresses weeds, which can outcompete your already stressed-out plants for resources. Smith recommends adding a two- to four-inch layer around the base of your plants for protection.
Offer Some Shade
If you’re cultivating a container garden, potted plants are particularly susceptible to drying out in heatwaves. To keep them as vigorous as possible, Smith suggests temporarily moving them to a shaded space. You can also arrange your pots in clusters, so they shade each other out, or use cardboard to block out the sun. As for flower beds and vegetable gardens, covering your plants with a shade cloth (burlap, umbrellas, or light-colored bedsheets will also work) will shield them during the hottest times of day.
Avoid Pruning
Although pruning is beneficial for faster, more abundant growth, snipping off decayed bits in the middle of a heatwave is ill-advised, since the plant is already under stress. “Avoid making pruning cuts to live tissue, as the combined stress with the heat may cause rapid decline or plant death,” Smith says. Instead, postpone your pruning task until late winter or early spring, depending on the type of plant.
Skip Fertilizing
Fertilizing your plants is another gardening chore that isn’t well-suited for a summer heatwave. During plants’ active growing season, applying a balanced fertilizer can create healthier growth and resist pests. Amid a heatwave, however, fertilizing can burn your plants or cause new growth that wilts quickly. “When plants have slowed their growth, the addition of fertilizers can increase the risk of burn to the roots, as well as encourage new growth that the already stressed plant cannot support,” Smith adds.
Ward Off Weeds
“Many weeds have adapted to grow in the harshest conditions, including high temperatures, and will still be thriving and utilizing resources while our desirable plants struggle,” smith says. Because summer weeds are aggressive and intrusive, they can outcompete your desired plants for water and nutrients, leaving them even weaker than before. To strengthen your plants against competing weeds, pull them early by the roots, so they won’t grow back. Wait to weed until temperatures have cooled, either in the early morning or late evening, to protect yourself and your plants from the heat.
Lilly Blomquist is the associate editor at The Pioneer Woman, where she writes lifestyle stories across a wide range of topics—including news, entertainment, holidays, food, and more.
