Heatwaves can ruin a garden but there are ways to protect it
The latest New Jersey heatwave may have done a number on people's plants, flowers, garden vegetables, herbs, and even lawns. The type of plant or vegetable, its root system, the type of soil used and how often it's watered, all influence how the plant responds to extensive heat. But there are ways to protect the garden this summer.
Why plants can't survive the heat?
Bill Hlubik, professor and Agriculture and Resource Management Agent for Rutgers Cooperative Extension of Middlesex County, said as temperatures soar into the 80s and 90s, plants respond differently to heat stress.
Each plant has its own set of protective mechanisms. They'll form these shock proteins that offers some level of protection. Each plant has its own level of protection. Some plants are more resilient to the heat than others. It could be it has a deeper root system or the origin of that plant was in an area of the world that was accustomed to those high temperatures.
He said plants respond to heat by transpiration. That's where they release water from the leaves. It's a natural mechanism similar to people sweating and releasing heat that way. Plants have that same mechanism. But during a heatwave, the plants can't keep up with the amount of moisture being released from its leaves. So the plants shut down which can lead to discoloration or brown leaf tips.
How can people protect their plants during a heatwave?
Hlubik said while there are certain types of plants, flowers, bushes, trees, vegetables and herbs that are more resilient to the heat, it really doesn't matter what is planted in a backyard. As long as people use mulches around the plant, whether it be organic compost material, peat moss, straw or bark mulches, two to three inches thick. That helps to reduce evaporation around the soil, helps to keep the soil and roots cool and helps to lock in moisture around those plants.
It's also important to respond before the heatwave actually hits, if possible. Hlubik said 24 to 48 hours before the heatwave arrives, adequately irrigate the soil so that there is moisture available. When the heatwave arrives, sometimes it's hard for the plant to take up that moisture availability, he added.
Make sure that there's plenty of air circulation in the area where there are plants. That will actually decrease temperatures. Shade certain plants such as azaleas and rhododendrons, which should have about 15% to 30% shade. Since they have shallow root systems, they should be watered often.
What plants respond well to the heat?
Plants like tomatoes, peppers, eggplants and asparagus are deep-rooted plants that like the heat, Hlubik said. However, they do not like the heat in the evenings. If those plants have too much heat in the evening hours, like other fruits or vegetables, their pollen may become non-viable or they may lose their flowers.
"There may be a certain amount of flower abortion," Hlubik said.
Trees like American Sweet Gum, Kentucky Coffee and Yellowwood are resilient to the summer heat and can bounce back quicker.
In terms of bushes, junipers, forsythias, lilacs and gray dogwood do fairly well under higher temperatures.
As far as flowers, lantana, cosmos, cleome, spider and straw flowers can withstand the heat.
Woody herbs such as rosemary, thyme, verbena and garden zinnias also thrive in hot, dry temperatures.
What about lawn care?
Use different lawn varieties with a deeper root system so they are able to access water down deeper than other types of grasses such as bluegrass and rye grass, Hlubik said. Many of these deeper root system grasses also have endophytes that can protect them from pest problems.
Grass tends to go into dormancy when it gets too hot and it doesn't get enough water. Hlubik said if the grass goes into dormancy, let it happen. Rainfall will return and the grass will emerge from dormancy. When the grass goes into dormancy, he said this is a protective mechanism to preserve itself and wait until natural rainfall returns.
When irrigating the lawn, he said do it early in the morning so no water is wasted. Irrigating late in the day can actually exacerbate disease problems on plants. With any plant, water on the leaves late in the day due to surface irrigation can increase the level of disease problems on those plants.