Beware of pin oaks, such as this. Once they’re afflicted with chlorosis which turns their leaves yellow, it's difficult to restore a nice, green color. If trees were royalty, oaks would be kings in our American landscape. Their strength, beauty and adaptability make them revered in our history and lore. The oak is our national tree, after all. The white oak is Illinois' official state tree.
Many people, however, don't like to plant oaks.
"Homeowners often choose other trees because they think that oaks grow too slowly. That is a myth," said Doris Taylor, plant information specialist at The Morton Arboretum. A young oak grows at a good pace, about a foot a year, according to Taylor.
"Give oaks a chance," said Taylor. "You may be first on your block to plant one!"
Oaks great benefits to planting oaks. They make beautiful shade trees, with their distinct lobed leaves, acorns and red fall color. They are long-lived and suffer less damage from high winds than other trees. Plus, diversifying your landscape with a wider variety of trees can prevent a new disease or pest from wiping out whole blocks of trees, like what's happened to elms and ashes.
Emerging research shows that planting in September or early October can be more successful than spring planting, according to George Ware, Arboretum researcher who has studied and bred oaks for more than 30 years.
He recommends four oaks: Swamp white oak, chinkapin oak, Hill's oak, and bur oak. These trees are eminently adapted to our soils and climate, although majestic bur oaks are best planted in golf courses and other large spaces. Some oaks have been bred for a narrow shape to fit smaller spaces.
White oaks (different from swamp white oaks) may have difficulty as young trees, but if they survive their early years, should do well in our climate, Ware says. Mulching them is vital.
Ware cautions against planting trees red oaks, which are susceptible to oak wilt, a disease that ravaged oaks in many Wisconsin towns. (Never prune an oak between April and July, the prime flight season for oak wilt fungus-carrying insects.) He also advises not to plant pin oaks. In our alkaline soil pin oaks get chlorosis, which turns leaves a sickly yellow.
Most old oaks in the Chicago area are at least 160 years old, according to Ware. "When you plant an oak tree," he said, "You are planting for future generations." But things may be heading in the wrong direction.
The Illinois Natural History Survey estimates the oak's reign as the dominant species in Illinois forests could end within the next 50 years.
When European settlers arrived in Northern Illinois in the early 1800s, they cleared out groves of sturdy oaks to make plank roads, fence posts, barns and railroad ties. That was the first in a series of changes that has affected oaks' ability to reproduce and thrive.
"Two hundred years of our changes weren't all bad -- that's why we are able to live here today. But some of those actions had consequences we didn't appreciate at the time," said Megan Dunning, Arboretum Manager of Natural History Education. "Oaks are more than just a stately and beautiful landscape tree; they are a critical part of our ecosystem."
Laurie Casey is a staff writer at the Morton Arboretum in Lisle.
Learn about the history of oaks in Illinois and their use in home landscapes in "Oaks in Your Environment," 9 a.m. to noon Sept. 27. Registration open now. Call
