The white oak is the state tree of Illinois. It was the dominant tree in the oak savannas common in northeastern Illinois before European settlement. Its crown rounds out into a lovely canopy and its leaves have curved lobes. Acorns appear annually in the fall and are much relished by squirrels. The white oak holds its leaves for an extended period, often into the winter. Fall color varies with year from brown to a wine-red. This majestic oak is noted for its longevity, with trees over 300 years old not uncommon.

The genus Quercus includes more than 600 species of the oak tree, of which 90 are native to North America; the Chicago Botanic Garden's collection contains more than 60 varieties and over 1,000 individual trees. Twenty oak species are native to Illinois.

Oaks are slow growing, long lived, hard wood trees that produce fruit we all know as acorns. Within the white oak group, acorns mature annually; in the red oak group, acorns take two years to mature (biennial). Oaks are often imposing shade trees at maturity and provide habitat and food for a variety of wildlife.