Mossy cup oak acorns
It's tree trivia time! Did you know that the acorn of the bur oak (Quercus macrocarpa) is North America's largest native oak acorn? A very large bur oak acorn might measure up to 2 inches in length. Most bur oak acorns are in the range of 1 inch to 1-1/2 inches in length.
The bur oak is sometimes called mossy cup oak, a name that refers to the fringe around the edge of the acorn cup. Usually, the cup covers about half of the nut, but occasionally, the cup will be so large that only the tip of the nut sticks out of the fringe. Another common name for the bur oak is overcup oak.
The twigs of bur oaks have corky ridges. If you click the photo above and enlarge it, you can see ridges on both sides of the twig, giving it an irregular, thickened outline.
This tree, and several other bur oaks he planted at the same time are now about 15 years old. At 25-30 feet, they are big enough that they are becoming significant trees in our landscape. They grew slowly at first because they were establishing their roots, but now they seem to be growing two feet or more annually. They have been bearing acorns for several years.
The bur oak, a member of the white oak family, is native to much of the eastern United States and part of eastern Canada. It commonly lives for several centuries and individuals trees in favorable conditions may live much longer. In maturity, it may reach 100 feet in height and in spread. Many creatures of the wild enjoy its acorns and some nibble the twigs as well.