Oak trees (Quercus spp.) take decades to mature. Depending on their own species, the trees are 20 to 30 years old when they create their initial acorns. Even then, acorn production isn’t constant from year to year. Factors such as freezing temperatures throughout blooming, excessive rain, windy conditions, drought and nutrition can affect acorn production. Larger canopied trees receiving more lighting create more acorns than smaller trees in shadier conditions. Most oaks are at their acorn production peak at 50 to 80 years of age. Subsequent to the oak attains 80, acorn production typically starts to decrease.
Acorn Development
Oak trees are monoecious, meaning each tree produces female and male flowers. The male flowers, or catkins, have long, drooping stems with several blooms on each stem. Wind and insects carry the male flowers’ pollen to the female flowers on neighboring oak trees. The female flowers, which appear about one week after the male flowers, are at the upper canopy of every oak and are so small that a magnifying glass is needed to identify them. Acorns from the white oak group of trees mature at one growing season, but acorns from the red oak group require 2 growing seasons to mature and drop.
Pin Oak
The pin oak (Quercus palustris) is a fast-growing red oak which starts to make its initial acorns after it’s 20 years of age. A span of just one or two years is involving important acorn crops after the tree matures. The almost-round acorns are usually 1/2 inch long, and each includes a shallow cap that features tight scales. Begin looking for pin oak acorns after the third week of August. The pin oak tree is hardy at U.S. Department of Agriculture plant hardiness zones 4 through 8.
Bur Oak
The bur oak (Quercus macrocarpa) is a white oak which does not produce its initial acorns until it’s 35 years old. The length between a mature bur oak’s abundant acorn crops is three to four years. The tree produces large acorns, and every one includes a spiky cap which covers one-half of the acorn. Due to their size, bur oak acorns are a top food alternative for deer, turkeys and other forest animals. Bur oak tree is hardy in USDA zones 3 through 8.
White Oak
The white oak tree (Quercus alba) produces its initial acorns after it’s 20 years of age but has its own peak production after 50 years of age. The span of time between its important acorn crops can be four to 10 years. The tree’s slender acorns are up to 1 inch long and have little caps. Falling to the ground in September and October, white oak acorns are an important food source for wildlife. White oak is hardy in USDA zones 3 through 9.