Droughts and prolonged heat waves are expected to become more common in the coming decades, with parts of the United States already experiencing what scientists call a “mega-drought.”
Droughts are periods of abnormally dry weather that persist for relatively long periods. Along with wider societal impacts, such as potential crop damage and water shortages, droughts can also have a devastating impact on garden plants.
So how can you take care of your garden during these hot and dry conditions?
How does drought damage plants?
Water stress occurs when water loss through leaves exceeds the plant’s ability to draw water through its roots, said Lucy Bradley, a horticulture scientist at State University Extension. from North Carolina. Newsweek.
It interferes with several important processes, including photosynthesis (the conversion of food into energy); transpiration (the movement of water through the plant and the evaporation of certain parts, which contributes to cooling it); the “turgid” pressure which makes the plant stiff and rigid; and the growth of root hairs, which suck water and nutrients from the soil.
Perhaps the most important effect of drought on plants is the reduction of photosynthesis, which is the process by which plants create food from sunlight, providing energy (in the form of sugar) to grow, produce flowers and fruit, and reproduce.
“Prolonged drought can cause the photosynthetic machinery to completely collapse, and it can take a long time for plants to rebuild their roots and internal mechanisms,” said Vijai Pandian, horticulture educator at the University of Wisconsin-Madison Division. of Extension. Newsweek.
“It can have long-term effects…and symptoms of the dryness effect often persist for [the] next few years,” he said.
In the short term, drought can lead to leaf wilting and scorching, leaf loss and branch dieback, among other symptoms, according to Heidi Kratsch, a horticulture specialist at the University of Nevada, Reno Extension.
“Over time, drought can weaken plants, making them less productive and more susceptible to insect pests and disease,” Kratsch said. Newsweek. “Drought-stressed plants can also create a fire hazard in wildfire-prone areas.”
What can you do to protect plants in times of drought?
According to Kristine Lang, a horticulture specialist at South Dakota State University Extension, effective water management is key.
“Once plants have been in the garden for several weeks and have established roots, deep watering once or twice a week to completely saturate the soil and encourage deeper rooting of established plants is more beneficial than light watering every days,” Lang said. Newsweek. Deep rooting helps plants survive drought conditions.
“When watering, it’s important to water the soil rather than wetting plant leaves, which can actually contribute to the spread of certain plant diseases,” Lang said.
In case of drought, it is recommended to water early in the morning when the air temperature is cooler to ensure that the water can reach the roots of the plants.
“Avoid watering when it’s windy because the wind increases evaporation of soil moisture and makes spray irrigation less effective,” Kratsch said.
Using a soaker hose or setting up a drip irrigation system when possible can also be beneficial. “Drip irrigation applies water directly to the soil where the roots are and minimizes excess water runoff onto unplanted or paved areas,” Kratsch said.
According to Pandian, the trees should be well soaked once or twice a week. During this time, newly planted trees and shrubs (between 1 and 3 years old) need to be watered twice a week to a depth of about one inch (0.6 gallons of water is needed to cover one inch of depth per square foot).
You can use a long screwdriver or a soil probe to test the depth of water movement in the soil.
For gardeners who have plants in containers, hanging baskets and pots, you may need to check to see if they need water every one to two days depending on the size of the container, Lang said.
Applying a layer of material to the surface of the soil, a technique known as mulching can also be beneficial. “Mulching the garden soil surface with an organic material such as straw or wood chips can help hold the soil and keep the soil surface around the plant cooler,” Lang said. “It also reduces weed competition which becomes even more important in drought conditions.”
Erecting temporary structures to provide shade around heat-sensitive plants can also help prevent excessive evaporation of water from the leaves.
“Heat-damaged leaves gradually appear reddish or brown in color and become dry and brittle to the touch,” Kratsch said.
Caring for plants on the go
If you’ll be away from home for several days, try moving potted plants to a shady, sheltered area if you don’t have anyone to water them while you’re away, Lang said.
In dry conditions, it is also important to eliminate any competition with the desired plants, which may include weeds; weak, diseased or stressed plants that are past their peak; and annuals that can easily be replaced, Bradley said. Also, don’t stimulate plant growth by fertilizing or pruning: “Growth taxes the whole plant and new growth is vulnerable,” she said.
Fertilizing drought-stressed trees and shrubs often stimulates more foliage at the expense of root growth, according to Pandian, who also recommended avoiding unnecessary transplants.
When it comes to the lawn, don’t worry too much if it begins to go dormant – noticeable as a brownish color – in excessive summer heat. Most lawns can survive two to three weeks of dormancy and will green again as temperatures drop.
“Small areas that don’t recover can be overseeded in the fall (unless drought is still present) or early spring,” Kratsch said. “An alternative is to learn to accept a less than perfect lawn (as Mother Nature intended). Do not fertilize lawns or other landscape plants during drought.
“For future drought years, consider replacing unnecessary lawns with plants that can better withstand the heat and low water.”