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Extension notes: Help your garden weather a heatwave

By: Rebecca Konopka
Carter County Extension Agent

If you think you’re hot, ask your plants (not literally). They can suffer under high summer heat, too. 

Most vegetables and native plants can withstand a periodic heatwave, but once the soil dries out in the top few inches, all plants can feel the stress. Some vegetables like beans and tomatoes may delay producing fruit during hot weather but this is usually temporary. A layer of mulch around your plantings can help hold moisture for those important surface roots and moderate the soil’s temperature. A light-colored mulch like straw, pine needles or grass clippings can help to reflect heat back and away from the plant’s roots. 

Water your plants in the early morning before the heat of day to prevent water loss to evaporation. If you use sprinklers, most of that water can be lost through wind drift and evaporation, so try to water on a calm morning. Hand watering gives you the best control and directs the water exactly where you need it. If you can, it is best to soak the soil directly beneath the plant and avoid getting the leaves wet. Soaker hoses are good for directing the water where it’s needed most. 

Watering in the morning also discourages slugs and fungal diseases. An evening dousing can leave the soil and foliage wet for longer periods of time and encourage snails, slugs and the spread of disease. 

You may have to water container gardens two or even three times a day, depending on how large the container is and how much foliage is present. If they are small enough to be moved, shifting containers to a place where they can get partial shade will help manage the plants’ stress, but some plants may not bloom as well when exposed to prolonged shady conditions. 

During normal weather, young trees need at least 10 gallons of water a week for the first three years directed toward their developing root systems. If you find yourself in a hot dry spell, provide your young trees and shrubs with more water. They are at their most susceptible during those early years. A tree bag which contains a reservoir of water that is released slowly to the plant can help keep the tree well-watered during the hottest spells. You’ll only have to fill the bag occasionally rather than watering every few days. They can be purchased at most garden shops. 

Shade cloth, which comes in varying thicknesses, can help protect plants that are withering under the sun’s rays. Support it above or to one side of the plants, which will shelter them like a porch protects us from the strongest sunlight. Tree branches with leaves can also be placed over plants to provide shade. 

Now is not the time to cut your lawns short. Mow them to at least a 3-inch height. That way, the grass blades will provide shade for their own roots and help hold in soil moisture. Avoid fertilizing lawns and gardens during heatwaves, because roots’ capacity for taking up nutrients are reduced during hot weather. You’ll just be wasting your money. Most Kentucky lawns are comprised of bluegrass and tall fescue. Once established, both of these species and withstand quite a bit of drought. 

Many cool-season crops are planted in August, but the late summer heat can be hard on young transplants. Again, shade cloth can come in handy. Or plant them under more mature plants, so they can benefit from the shade the larger plant throws. 

For more information about how to weatherproof your lawn and garden, contact the Carter County office of the University of Kentucky Cooperative Extension Service. Educational programs of the Cooperative Extension Service serve all people regardless of economic or social status and will not discriminate on the basis of race, color, ethnic origin, national origin, creed, religion, political belief, sex, sexual orientation, gender identity, gender expressions, pregnancy, marital status, genetic information, age, veteran status, or physical or mental disability. 

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