A dry spring means it’s time to water

Summer is off to a dry start in the Chicago region, which means it’s time for watering.

“May was very dry, so plants need more watering than we might be used to doing at this time of year,” said Sharon Yiesla, plant knowledge specialist at The Morton Arboretum in Lisle.

The dry weather is coming at a critical time, soon after spring planting. New plants have not yet grown many roots that can collect and store water, so they need a steady supply of water to help them get established. “Dry conditions are even harder on new plants than they are on established plants,” she said.

According to the office of the Illinois State Climatologist, northeastern Illinois was much drier than usual in May, and continuing hot, dry weather would make matters worse. It’s not just whether you water your garden that makes a difference to plants. It’s also how you water.

“Sprinkling a little bit every day doesn’t really help,” Yiesla said. “That will only dampen the surface. The water won’t get down to where the plants’ roots are.” Instead, water each area of the yard deeply, enough so the water soaks into the soil 4 to 6 inches. You can water a different area each day, so each area gets a deep soak every few days.

Here are tips from the Plant Clinic for watering. Find more detailed advice at mortonarb.org/how-to-water.

Get the water to the roots. There is no reason to water the leaves of a plant. Instead, apply water to the soil, where the roots are.

Check the soil for moisture. Since plants absorb water through their underground roots, the amount of water in the soil is what matters to them. “If you dig down a couple of inches and the soil feels dry, or if even if the surface feels dry and hard, it’s time to water,” Yiesla said. Bear in mind that soil conditions may not be the same in all parts of your yard.

Check new plants and recently planted trees often. Give these plants extra attention on watering. For a new tree, apply water both to the root ball, right around trunk, and to the surrounding area. Irrigation bags or soaker hoses can make it easier to water trees slowly.

Water slowly and deeply at intervals. To water an established tree, let a hose run slowly on the soil in the area under the branches, moving it around occasionally. To water a lawn or a garden, let the sprinkler run for half an hour or more until moisture has soaked down 4 to 6 inches.

Apply about as much water as 1 inch of rain a week. You can time how long your sprinkler or sprinkler system takes to deliver that much water by placing a straight-sided container under the spray and let it fill to a 1-inch depth. If you deliver the equivalent of 1 to 2 inches of rain, the water will percolate into the soil about 6 inches, reaching the fine water-absorbing roots.

Water container plants more frequently. Because there is little soil to hold water around their roots, container plants can dry out and wilt fairly easily. If containers are in full sun, the plants will likely require more frequent watering than containers in shade.

Spread mulch. A layer of organic mulch such as shredded bark or leaves will help keep moisture from evaporating from the soil. Apply mulch in an even layer around trees and shrubs and over garden beds. Spread mulch 2 to 4 inches deep. Do not let it touch the trunk of a tree or the stems of shrubs.

Monitor the soil, not the weather forecast. “Just because rain was forecast doesn’t mean it rained,” Yiesla said. Even if it did rain in a nearby area, the rain may not have reached your yard, or not enough may have fallen to make a difference to your plants. “Keep checking the soil your plants are growing in to see how dry it really is,” she said.

For tree and plant advice, contact the Plant Clinic at The Morton Arboretum (630-719-2424, mortonarb.org/plant-clinic, or plantclinic@mortonarb.org). Beth Botts is a staff writer at the Arboretum.