Adequate moisture is critically important to landscape plants during hot weather, but too much rain or excessive watering can bring problems. Wet soil combined with high temperatures can create stressful conditions for bedding plants, vegetables, shrubs and even trees, especially those planted this year.
When the soil is saturated, pore spaces, which normally hold air, are filled with water. Since the plants’ roots get the oxygen they need from the air in those spaces, the roots literally can drown in soil that’s waterlogged over an extended period. A sick root system leads to a sick plant. Plants affected by wet soil or root rot might look wilted even though the soil is moist.
Wet conditions encourage fungus organisms living in the soil to attack the roots or crown — the area where the stem enters the soil — of a plant, thus causing rot. Worse yet, once infection occurs, little can be done to help the affected plant.
Fungal diseases that attack the foliage of many plants thrive in rainy weather. Black spot on roses is prevalent, even on resistant varieties, and control is nearly impossible if it rains every afternoon. Cercospora leaf spot on crape myrtles causes the leaves to turn yellow or red and drop off. The disease is not fatal, and the trees will recover without sprays, but flowering might be diminished.
Plants with succulent stems, such as impatiens and begonias, as well as those that like cooler temperatures, such as geraniums and dianthus, and those that prefer drier, well-drained soils, such as Indian hawthorns, are particularly susceptible to root rot.
Gardeners can take steps to help alleviate the problem. Adjust the automatic timers on your irrigation systems. I often see sprinklers unnecessarily watering the day after a heavy rain because of timers. Turn them off when it’s rainy, and turn them on only during drier conditions.
Keeping your beds well mulched will control weeds and maintain soil moisture, but if you find they’re staying too wet, pull back the mulch from around plants or remove it entirely to allow the soil to dry faster.
Pests like snails and slugs reproduce rapidly during rainy weather. These pesky critters chew holes in leaves and flowers and are particularly fond of soft-leaved plants, such as impatiens, begonias and hostas. Try not to let their populations get out of control. Toads in your garden feed on slugs and should be left alone. Numerous baits on the market help control snails and slugs, or you can place a bowl in the ground up to its rim and fill it halfway with beer to attract and drown them.
Frequent rain can leach nutrients from the soil, so evaluate your landscape plantings and fertilize, if needed. Plants growing rapidly now, such as lawn grasses, summer bedding plants and tropicals, are especially vulnerable.
A soil test will tell you what and how much fertilizer to apply. The UGA Extension in Cobb County can help with testing: https://bit.ly/417dAUE.
The Master Gardener Volunteers of Cobb County supports the University of Georgia Cooperative Extension Service and strives to improve the quality of life in our community by delivering research-based horticultural information, educational programs and projects.
– Master Gardener Volunteers of Cobb County is a part of the University of Georgia Extension.
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