Information on the Bur Oak Tree

Geography and Growing Conditions

• This oak displays solid tolerance for drought throughout its wide range, which begins in U.S. Department of Agriculture Plant Hardiness Zone 3 extending to zone 8. Bur oak grows in a variety of different kinds of soils from south-central Canada south into the Dakotas, eastern Nebraska, eastern Kansas and most of Oklahoma and central Texas. The eastern border of its range includes much of the Great Lakes region, as well as Ohio, Indiana and western Kentucky. Bur oak does best in full sunshine.

Size and Form

• The size makes it too large for even a medium-sized yard, since some individuals of this species grow to 150 feet. Most are between 60 and 90 feet with trunk diameters from 2 to 4 feet. The bur oak has a stout trunk with sturdy branches growing upright at first but spreading out creating a rounded canopy as the tree ages.

Leaves

• As many as nine or as few as five lobes exist on the leaves with most leaves having the appearance of possessing a "waist" where the middle lobes indent to the leaf's center. The lobes vary in size with no uniform appearance. The foliage develops between 6 and 12 inches long with a leathery texture. The leaves are dark and vibrant hues of green, except in the fall, when they change to a lighter shade or a yellowish-brown. Unlike some oaks, all the leaves come off a bur oak in the autumn months leaving the tree bare.

Bark and Acorns

• The bark of bur oak, which is the state tree of Illinois, is thick and a light tint of gray. The deep furrows highlighting the bark give the tree winter interest. These ridges run longitudinally on the trunk, making the tree stand out in a landscape from a distance. The acorns require just one growing season to mature, but it may take as long as 35 years for a bur oak to yield its first crop of the large fruits.