Our dry, hot weather is abnormal but don’t panic yet
Tim Johnson, Chicago Botanic Gardens horticultural director, shows plants that do well in the drought. The Cercis Canadensis trees in the parking lot are wilting a bit due to the hot weather and lack of rain. |Tamara Bell~Sun-Times Media.
Updated: July 22, 2012 7:38PM
With the Chicago area wilting under one of the warmest springs and driest Junes on record, it’s no surprise to find gardeners and homeowners beginning to panic just a bit about their lawns and flower beds.
The first thing they should do, say specialists familiar with the art and science of growing things, is chill out. With a little bit of common sense and patience (and less water than you might expect) lawns and gardens can survive stretches of hot dry weather, several said this week.
“I’ve been getting lots and lots of (plant) samples in our diagnostic center from people realizing that something is wrong, and the problem is, of course, lack of rain, lack of water,” Jennifer Brennan said. “And too much heat.”
Brennan, chief plant diagnostician for the Chalet landscape and gardening center in Wilmette, said growing glitches began in March, with a stretch of unusually warm weather that coaxed flower buds and tree leaves into bloom far earlier than they should have opened. Diseases and insects also followed the sped-up schedule.
“And we’re seeing early, early stress on plants,” she said. “But really, it’s not so much because of the heat as it is the lack of water.”
That lack of water is a reality. Records show that our area got only .01 inches of rain in the first two weeks of June, compared the usual period average of 1.8 inches.
Still, northeastern Illinois, including Chicago, Cook County and the five collar counties, aren’t dealing with the drought situation now facing corn and soybean farmerscentral and southern Illinois, said Mike Timlin of the University of Illinois’ Midwestern Regional Climate Center in Champaign. In contrast, our area is simply labeled “abnormally dry” according to the National Weather Service’s U.S. Drought Monitor, Timlin said.
Although heat is not always part of a drought situation — something many people don’t realize, he said — it is part of the current dry spell: “If you look at our rainfall numbers, they are lower than normal, but not so much as to explain the level of dryness we’re experiencing.”
“Most of the rain’s we’ve had this spring have been pretty spotty. Rockford might get rain, but maybe it stops short of Chicago. But the northern part of the state has probably gotten more of those shots of rain than elsewhere.”
Proximity to Lake Michigan plays a part, he said, since lake breezes can affect precipitation, knocking down seasonal extremes. The lake actually tends to “hold off” seasons, Timlin said.
Tim Johnson, horticulture director at the Chicago Botanic Garden in Highland Park, advises taking a laid-back attitude to the weather forecast.
He and his staff regularly juggle the water and heat needs of hundreds of different types of plants; for instance, placing mulch around their roots conserve moisture. But lawn and garden care isn’t a monolithic task, he said. Some plants survive or thrive on hot dry weather. Others don’t. And the type of soil in which they’re planted also affects their health. Some plants do well in dry sandy soil, others prefer heavier clay or loam soils, so it’s good to know a bit about your soil as well as your plants.
He also advised cutting grass no shorter than about 3 or 3.5 inches. It’s what he does at home. His lawn stays greener than those of his neighbors, “and I don’t have to mow as often,” he joked.
Johnson and Bill Leuenberg, landscape and turf specialist at the Chalet, champion the “water deep, not often” rule, as does Leuenberg’s colleague Brennan.
“People need to understand the way turf grows. You get to these points where it’s very dry, and all of a sudden they think that have to make up for it,” Leuenberg said.
While lawns, especially the opular bluegrass-style lawns, do prefer cool weather, and do go brown and dormant in the heat, it doesn’t mean they’re dying, he said. It’s a natural state; with deep watering once or twice a week, the lawn will survive.
In actuality, watering every day can chase oxygen from shorter grass root systems, Brennan said.
Of course there are always exceptions to any rule. Johnson said vegetables and annual plantings need more water, especially during prolonged bouts of heat. And he suggested paying a little more attention to anything planted within the past three years.
Lawns, too, should get a little more care during hot spells; go from one inch per week to maybe 2.5 inches a week if the temperature rises to 90 degrees and stays there, Leuenberg said. Brennan’s rule of thumb is to add half an inch of water per week for every 10 degrees the mercury stays above 75 degrees.
Ultimately, anxious homeowners should remember another thing, Timlin said: “What we’re dealing with is a short-term thing.”