How to protect your trees and plants from heat, drought damage

  • The recent lack of rain and a late-September string of seven days in a row above 90 degrees are causing grass to turn tan and crunchy and some trees, such as this maple at Fullersburg Woods near Oak Brook, to prematurely lose their leaves.

      The recent lack of rain and a late-September string of seven days in a row above 90 degrees are causing grass to turn tan and crunchy and some trees, such as this maple at Fullersburg Woods near Oak Brook, to prematurely lose their leaves. Daniel White | Staff Photographer

 
 
Updated 9/29/2017 5:52 PM

With late-September heat and lack of rain, our weather patterns have not been playing nice with the trees and plants that traditionally make fall a colorful time to be in nature.

The region endured seven days in a row of record-breaking heat that ended Tuesday, with high temperatures of 92 to 95 degrees, according to the National Weather Service.

                                                                                                                                                                                                                       
 

That put added stress on lawns and trees already struggling after receiving only about one-third of an inch of rain for the entire month.

While the Weather Service says the average temperature for September hasn't topped the average for August, at 70.4 degrees and 71.5 degrees, respectively, arborists and plant life specialists say the conditions are far from ideal.

Crunchy brown maple leaves are a common sight across the suburbs as trees respond to a lack of rain and a string of seven 90-plus-degree days from Sept. 20 to 26. Arborists say trees need between 1 and 2 inches of water each week to prevent drought damage.
  Crunchy brown maple leaves are a common sight across the suburbs as trees respond to a lack of rain and a string of seven 90-plus-degree days from Sept. 20 to 26. Arborists say trees need between 1 and 2 inches of water each week to prevent drought damage. - Daniel White | Staff Photographer

Maples, locusts, evergreens, lawns and bright fall mums are dropping their leaves early, turning tan and crunchy, or wilting when they should be blooming, experts say. But there is a remedy -- good ol' H2O.

"For those of us who love fall color, in order to preserve those leaves on our trees and shrubs, we need to be watering our plants now," said Boyce Tankersley, director of living plant documentation at the Chicago Botanic Garden in Glencoe.

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Here are tips on preserving plant life from Tankersley and two other experts: Scott Strigner, a certified arborist with Bartlett Tree Experts in Bolingbrook, and Sharon Yiesla, plant knowledge specialist at the Morton Arboretum's Plant Clinic in Lisle.

What to water

• Deciduous trees, including honey locusts, lindens and maples: Honey locusts that don't get frequent watering have dropped nearly all of their leaves already. Lindens, which have been hit hard by Japanese beetles this year, also are losing their leaves early. And the leaves of many maples are starting to curl from the stress of the drought, which the National Integrated Drought Information System ranks as "abnormally dry."

"They're the most obvious," Stringer said about maples, "because their leaves will turn crispy brown, hang on for a little bit, then start falling off."

• Evergreens: They won't show it, but evergreens can slowly go dormant from lack of water, which they can't drop their leaves to conserve. Austrian pines and spruces are hit hard by drought, which can attract insects that cause further harm.

                                                                                                                                                                                                                       
 

• New plantings: Anything planted this spring or summer needs time and water to establish its root system and steel itself against damage from bad weather conditions.

• Grass: If it's crispy and crunchy, it needs a drink.

"It's quite normal for lawns to not be looking pristine right now. A little bit of tan color in your lawn is not anything to be concerned about," Tankersley said. "If your lawn is totally tan and has no green, do some deep watering and try to get some of that color back."

• Plants in containers: These can wilt easily if the soil in the container is too dry.

How to water

• Take it slow: Strive to give trees about 1 to 2 inches of water each week. This can come in one or two sessions of 45 minutes to an hour. Use a rain gauge to determine a more exact watering time. Prolonged watering allows moisture to sink deep into a tree's roots, about 6 to 18 inches below ground, where most liquid is absorbed.

• Flush out salts: For plants in containers, Tankersley recommends watering until moisture runs through all of the soil and drips out the bottom of the container. This removes any drying salts that may have built up in the soil.

Some species of trees, such as this maple at Fullersburg Woods near Oak Brook, are shedding their leaves about three weeks early because of recent high temperatures and a lack of rain. Arborists say maples show drought issues most obviously because their leaves quickly turn brown and crunchy, then begin to fall.
  Some species of trees, such as this maple at Fullersburg Woods near Oak Brook, are shedding their leaves about three weeks early because of recent high temperatures and a lack of rain. Arborists say maples show drought issues most obviously because their leaves quickly turn brown and crunchy, then begin to fall. - Daniel White | Staff Photographer

• Hit the right spot: Water deciduous trees not just at the trunk, but out to the "drip line," which Stringer describes as the outside edge of the leaf canopy. Be careful not to oversoak the trunks of evergreens, which can cause rot.

• Keep it up: Continue weekly or twice weekly deep waterings at least until the region receives a rain of 1 to 2 inches. Stringer recommends deep watering until the first freeze -- even after trees have shed their leaves.

Plant health tips

• Don't fertilize: Fertilizers contain salts, which can further dry out soil.

• Use mulch: Wood mulch can help retain moisture around roots. To properly apply mulch, spread a thin layer starting 3 inches from the trunk and extending to the edge of the leaf canopy.

Future outlook

Drought and heat both can harm trees by hurting their roots.

"It's not like your tree is going to die today. Root damage could affect your tree for years to come," Yiesla said. "Anything that's impacting the root system of the plant always has long-term effects."

This year's late hot spell compounds a series of other weather conditions in recent years that have harmed trees, such as a drought in 2012 followed by flooding in 2013 and "polar vortex" cold conditions in 2014 and 2015.

"We're already seeing decline because of that environment," Yiesla said. "This would add one more layer."

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