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University of Illinois Extension serving DuPage, Kane and Kendall Counties

Main Office (Kane County)
535 South Randall Road
St. Charles, IL 60174-1591
Phone: 630-584-6166
FAX: 630-584-4610
Email: uie-dkk@illinois.edu
Hours: Monday - Friday 8:30 am to 4:30 pm Master Gardener: M-F 10 am to 2 pm

Branch Office (DuPage County)
1100 E. Warrenville Road
Suite 170
Naperville, IL 60563
Phone: 630-955-1123
FAX: 630-955-1180
Email: uie-dkk@illinois.edu
Hours: M 11am - 7pm; Tu-Fri 8:30am-4:30pm Master Gardener: Tu-W-Thu 9 am to 12 pm

Branch Office (Kendall County)
7775-B Illinois Route 47
Yorkville, IL 60560
Phone: 630-553-5823
FAX: 630-553-5871
Email: uie-dkk@illinois.edu
Hours: Monday - Friday 8:30 am to 4:30 pm Master Gardener: M-F 9 am to 12:30 pm

News Release

Dry Weather Warning: Even Large Trees Get Stressed

ST. CHARLES, Ill. – The recent pattern of dry and hot weather could not only stress recently-added trees and plants, but it may unveil asymptomatic trees still recovering from the 2012 drought.

“In northern Illinois, we currently are in an extended abnormally dry period,” said Richard Hentschel, Horticulture Educator with University of Illinois Extension. “Homeowners need to pay attention to those trees and plants that seem to take care of themselves, as well as those new additions from this growing season.”

According to the Illinois State Water Survey (ISWS), “dry weather in August and September has led to low soil moisture across Illinois.” Moisture levels declined 84 percent at the 2-inch level and more than 10 percent at depths up to 20 inches. In addition, the ISWS reports only 2.02 inches of precipitation for the St. Charles research station from Aug. 2 to Oct. 2 this year. In the same period in 2016, the station recorded 6.26 inches.

Established trees, evergreens, shrubs and perennials need supplemental water in these conditions. Five years later, the drought of 2012 still impacts local trees, and this new extended dry period adds to that stress.

“While large established plants may appear to be OK, a lot of them really are not,” said Hentschel. “I was able to examine a cross section of an oak taken down mid-summer and could readily see the growth rings from the spring of 2017 and back. Prior to 2012, the rings were wide and evenly spaced indicating good growth rates. From 2012 forward, the rings were very tight together, indicating slowed growth. Until the tree died, the leaves appeared normal, according to the homeowner who had no idea the big beautiful oak was in trouble.”

While homeowners cannot evaluate tree rings, Hentschel said they can go out and examine branches to see how much annual growth they are putting on.

“This mirrors the rings in the trunks. You will need to examine quite a few branches to get a good idea on the average growth overall,” Hentschel said.

“To hydrate these big trees, first, leave the sprinkler on the shelf. It will take several hours of water per tree using an open-ended hose with a strong flow. Sprinklers simply cannot provide the volume.”

Keep these things in mind:

  • The majority of tree roots that absorb water do so in the top 12 to 18 inches of soil, so do not just wet the surface.
  • For deciduous trees, place the hose within the tree’s general drip line (canopy edge) and mentally divide the area up into quarters letting the hose run for an extended period in each quadrant.
  • Run the hose for at least 45 minutes or more in each quadrant at the biggest rate of flow possible without causing runoff.
  • Evergreen trees do not have as extensive a canopy, but watering them is very similar, just in a smaller diameter.
  • Evergreen needles lose moisture all winter so supplying them with as much water as possible as late as possible really helps.

“You should not forget your established shrub borders either,” Hentschel added. “Watering a bed is not as exacting. Move the hose around in the bed until you feel there is water everywhere. Often times placing the hose between the shrubs works the best.”

For more information on University of Illinois Extension programs and services in DuPage, Kane or Kendall County, visit go.illinois.edu/extensiondkk.

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University of Illinois/U.S. Dept. of Agriculture/Local Extension Councils Cooperating

Source: Richard Hentschel, Extension Educator, Horticulture, hentsche@illinois.edu