Prolonged droughts and heatwaves are expected to become more common in the coming decades, with parts of the U.S. already experiencing what scientists call a "megadrought."

Droughts are periods of abnormally dry weather that persist for relatively long periods of time. Aside from the wider societal impacts, such as as potential damage to crops and water shortages, droughts can also have a devastating impact on garden plants.

So how can you care for your garden during these dry and hot conditions?

Drought stress occurs when water loss through the leaves exceeds the plant's ability to pull in water through its roots, Lucy Bradley, a horticultural scientist at North Carolina State University Extension, told Newsweek.

This interferes with several important processes including photosynthesis (the conversion of food to energy); transpiration (the movement of water through the plant and evaporation from certain parts, which helps to cool it); the "turgor" pressure that makes the plant stiff and rigid; and the growth of root hairs, which pull in water and nutrients from the soil.

Perhaps the most significant effect of drought on plants is the reduction in photosynthesis, which is the process through which plants create food from sunlight, providing the energy (in the form of sugar) to grow, produce flowers and fruit, and reproduce.

"Extended drought can lead to the total collapse of the photosynthetic machinery and it can take long time for the plants to rebuild their roots and internal mechanisms," Vijai Pandian, a horticulture educator at the University of Wisconsin–Madison Division of Extension, told Newsweek.

"This can cause long term impacts ... and the drought effect symptoms often continue for [the] next few years," he said.

In the short-term, drought can lead to leaf wilting and scorch, the loss of leaves, and the dieback of branches, 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 told Newsweek. "Drought-stressed plants can also create a fire hazard in wildfire-prone areas."

According to Kristine Lang, a horticulture specialist at South Dakota State University Extension, managing water effectively is key.

"Once plants have been in the garden for several weeks and have established roots, watering deeply one to two times a week to fully saturate the soil and encourage deeper rooting of established plants is more beneficial than a light watering every single day," Lang told Newsweek. Deep rooting helps plants to survive drought conditions.

"When watering, it's important to water the soil versus getting the leaves of the plants wet, which can actually contribute to the spread of certain plant diseases," Lang said.

During drought conditions, watering early in the morning when air temperatures are cooler is recommended to ensure that the water can get to the plant roots.

"Avoid watering when it is windy, as wind increases evaporation of soil moisture and makes spray irrigation less efficient," Kratsch said.

Using a soaker hose or setting up a drip irrigation system where possible can also be beneficial. "Drip irrigation applies water directly to the soil where the roots are and minimizes run-off of excess water onto unplanted or paved areas," Kratsch said.

According to Pandian, trees should be given a good soaking once or twice a week. Meanwhile, newly planted trees and shrubs (between 1-3 years old) need twice a week of watering to a depth of about one inch (0.6 gallons of water is needed to cover an inch deep per square foot).

You can use a long screwdriver or soil probe to test the depth of water movement into the soil.

For gardeners who have plants in containers, hanging baskets and pots, you may need to check whether 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 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 retain soil and keep the soil surface around the plant cooler," Lang said. "This also reduces competition from weeds which becomes even more important during drought conditions."

Erecting temporary structures to provide shade around heat sensitive plants can also help to prevent excess water evaporation from leaves.

"Heat-damaged leaves appear progressively reddish or brown in color and become dry and brittle to the touch," Kratsch said.

If you are away from the house for several days, try to move potted plants to a sheltered shaded area if you don't have anyone to water them while you are gone, Lang said.

During dry conditions, it is also important to to remove all competition to desired plants, which can include weeds; weak, diseased or stressed plants that are past their prime; and annuals that can easily be replaced, Bradley said. In addition, do not stimulate plant growth by fertilizing or pruning: "Growth taxes the entire plant and the 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 transplanting.

When it comes the lawn, don't worry too much if it begins to go dormant—noticeable by a brownish color—in excessive summer heat. Most lawns can survive two to three weeks of dormancy and will green up again as temperatures cool.

"Small areas that don't recover can be over-seeded in the fall (unless drought is still present) or in 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 lawn areas with plants that can better handle heat and low-water conditions."

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