Quercus marcocarpa, the bur oak, is the tree featuring the largest acorns of any North American oak species, notes the “National Audubon Society Field Guide to Trees: Eastern Region.” In comparison to the fruits of other oaks, they are huge. Contributing to the size of the acorns is a large, fringed cup, which Tree New Mexico describes as similar in appearance to the spiny covering on a chestnut. Bur oak works well as a shade and lawn tree in areas with enough space to support its potential size.
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Bur oak grows between 60 to 80 feet, with trunk diameters between 2 and 4 feet. The tree has a rounded crown of sturdy branches. Bur oak leaves develop to lengths of 10 inches, with between five and nine lobes on each leaf. The dark green leaves change to shades of yellow brown in the autumn. Bark is a light gray color, with deep furrows.
This species of oak acquired its name from its acorns, with the fringed cup responsible for this. The acorns themselves are quite big when compared to most oak trees, growing to lengths of 1 1/2 and 2 inches. The oval fruits come encased in a scaly covering, with the gray, hairy scales having points that come down on the bottom border to create a fringe-like appearance.
It takes just one growing season for the acorns on a bur oak to mature before they drop to the ground. Every 3 to 5 years a heavy crop of the fruits occurs. The meat inside the shell is sweet, and wildlife including thirteen-lined ground squirrels, wood ducks, red squirrels, white-tailed deer, mice and cottontail rabbits partake of it as part of their diets. A bur oak begins to generate acorns at about the age of 35, according to the National Forest Service, with some trees able to produce a crop until they are 400 years old.
The bur oak is not a difficult tree to grow. It tolerates many different sorts of soil types, developing in acidic, alkaline, damp or dry areas. Bur oak requires full sunshine. It withstands exposure to urban conditions. The tree has the ability to do well despite drought. A native tree in eastern and central North America, it grows between U.S. Department of Agriculture plant hardiness zones 3 through 8.