How to Care for Houseplants During Extreme Heat, According to a Pro

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Summer may be a season of green but the extreme heat poses a specific set of challenges for famously fickle indoor plants. Caring for houseplants during summer requires special considerations to avoid leaf burn, mold, infestation and other conditions that can kill your favorite fern or ficus. 

To find out how to care for plants during summer and extreme heat, we turned to an expert, online plant dealer Sarah Doyle, who sells greenery and other goods via her digital storefront YayasPlantShop on Palmstreet. Doyle stresses to plant owners to take special care during hot and humid months when bacteria, fungus and plant-eating insects thrive.

Here are her top tips for keeping plants alive during summer.

Address mold and fungus 

Mold can take your plants down quickly and in no time does it thrive more than summer. "If you notice mold on the soil surface, usually white in color, mix one part hydrogen peroxide with eight parts water," Doyle says. "Place this solution in a spray bottle and mist the soil's surface four to five times a day. Fungus can thrive in moist environments, especially with alternating warmth and air conditioning. This method helps to reduce mold without harming the plant."

Adjust your watering routine

Proper watering is the most common cause of plant death. "In the summer, indoor plants need significantly less water than outdoor plants," Doyle told me. "Air conditioning helps keep the soil moist, so be mindful not to overwater and cause root rot. 

Water less frequently in summer and use the fingertip test to check if the top inch of soil feels dry to the touch before the next watering. To avoid overwatering, double the time between your usual watering schedule. The best time to water is early in the morning or late in the evening to minimize water loss through evaporation

Sunlight management

Doyle suggests keeping a watch on how much sun plants get in summer too. "Use sheer curtains to diffuse intense sunlight, preventing leaf burn, and rotate plants every few days to ensure even light distribution. Watch for signs of excessive light, like yellowing or browning leaves, and adjust their placement as needed. Seasonal changes may require repositioning, and UV-blocking window films can help reduce light intensity. 

Succulents and cacti do well in south or west-facing windows, while ferns and philodendrons prefer indirect light from east or north-facing windows. These strategies will keep your houseplants healthy and vibrant throughout the summer.

Fertilize regularly

Summer is a prime growing season for many houseplants, so it's a great time to fertilize. Use a balanced, water-soluble fertilizer every two to four weeks to provide essential nutrients. A few of the best indoor fertilizers include: Miracle-Gro, Espoma and Back to the Roots. Be cautious not to over-fertilize, as this can harm the plant. Dilute the fertilizer to half the recommended strength to prevent nutrient burn.

Repot if you see water damage or gnats

If you notice signs of water damage, such as yellowing leaves, a sour smell from the soil or an infestation of gnats, it's time to repot your plant. Gnats are often attracted to damp, decaying organic matter, indicating that the soil is too wet. 

Gently remove the plant from its pot, inspect the roots for rot, and trim any damaged areas. Repot with fresh, well-draining soil to promote healthy root growth. 

Additional tips: Avoid overwatering by allowing the soil to dry between waterings and ensure your pot has adequate drainage holes. If the plant is still healthy, but experiencing gnats, you can use Neem oil and spray regularly to kill the eggs and control reproduction.

Control the humidity

Many houseplants, especially tropical ones, prefer higher humidity levels. To maintain adequate humidity, group plants together, use a humidity tray with water and pebbles, or place a humidifier nearby. Misting the plant's leaves can also help, but avoid overdoing it, as too much moisture can lead to mold growth.

Rotate plants 

Rotate your plants every few days so all sides receive equal sunlight. This helps prevent uneven growth and keeps the plant well-balanced. Rotating your plants also reduces the risk of leaf burn caused by prolonged exposure of the same leaves to direct sunlight. This is especially important for plants with delicate foliage.

For more houseplant tips, check out our list of hard-to-kill houseplants and find out which plants keep bugs away.