Keeping plants happy through heat waves

Story by Jillian Ellison

June 14, 2022

eatwaves can be sporadic throughout the summer months, but while we work to keep our bodies hydrated, gardens could also use a bit of tender love and care during scorching temperatures.

Karen Mitchell, consumer horticulture extension specialist, said while the crops and plants grown in Indiana are usually adapted to the highs and lows of late spring and summer months, plants at certain development stages can still take a hit if not cared for properly. One of the bigger mistakes growers typically make during a heat wave is overwatering.

“You’ll think that because it’s really hot out that the plants must be extremely thirsty, but some plants will sort of close-up shop when it gets too hot out,” Mitchell said. “When they shut down like that, they aren’t using as much water, so it isn’t necessary to water them every single day.”

Deep watering every three days is sufficient, Mitchell said, with potted plants being watered from the bottom by soaking the pots in a container of water.

“You need to make sure the water is actually penetrating all the way through the soil,” she said. “Watering for just a few minutes on the soil surface isn’t sufficient.”

If you planted trees this spring, Mitchell said extra care will be needed for those saplings.

“Deep watering is even more important for trees, because you want the roots to grow down deeper into that moist soil,” she explained. “Once a week is sufficient, but you want to water at a slow trickle from your hose. Watering with the hose on full blast is going to cause all that water to run off rather than infiltrate that soil.”

Moments like this in the weather are crucial for mulch, Mitchell said, as wood mulch works as an excellent temperature regulator, keeping the water in and the heat out.

“Having a solid two to four inches around trunk, but not touching the trunk, of your trees creates an excellent barrier against the hot air,” she said.

Watering plants in the early morning is key, rather than in the evenings, due to when and how plants photosynthesize.

“Plants don’t photosynthesize in the evenings, so they aren’t going to be utilizing as much of that water you’re giving them,” Mitchell said. “Another reason it is better to water in the mornings is because the sun’s out to dry up what water the plant doesn’t use. Standing water left overnight can result in disease and fungus.

“Right now is not the time to fertilize, either, because the plant is stressed,” Mitchell said. “They may show signs, like curling leaves, but it’s important to keep in mind that it’s unlikely to be disease,” she said.”

It’s also important to remember, Mitchell said, that no matter what you do in extreme heat, plants may still show mild signs of distress, but typically bounce back.

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