The blue jays are happy, the squirrels scamper around with their cheeks stuffed and deer congregate at the base of the oak trees (Quercus spp.) in your woodland garden. The occasion is the ripening acorns that are dropping from the trees and onto the ground, providing the massive food supply for the oncoming winter months. August or September through October are the months for gathering acorns, and one look at the number of acorns and their color tells you a lot about the health of the tree and how it reacted to the previous months' weather conditions.
Mature acorns, which are typically tan, fall off trees in August thorugh October. If the acorns are green, it can mean the tree is having a problem, possibly stress, and if the summer was extremely hot or overly wet, premature acorns will drop.
Acorn Harvest Timeline
Oak trees start acorn production when the weather warms in spring. Oak trees have both male and female flowers on the same tree, making them capable of self-pollination and producing acorns.
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The long worm-like tendrils drooping from the limb are the male flowers, and the females are tucked almost invisibly under the tree's crown. Once pollinated, either by wind or insects, an acorn starts to develop, and during a normal-weather year, that acorn matures and falls by autumn.
External Factors Affecting Acorns
When a spring freeze kills the acorn flowers, the acorn crop will be small if it happens at all. High winds and excessive rainfall also interfere with the reproduction cycle, as does an influx of insects.
If green acorns develop without turning brown, that's the signal that the tree is under great stress and its energy is driven toward sustaining itself instead of producing healthy acorns. Drought conditions will force the flowers and leaves to close up their pores to save water, preventing pollination.
Oaks and Harvesting Acorns
The typical healthy oak tree produces acorns when it's about 20 years old, but its period of peak acorn production generally occurs when the tree is from 50 to 80 years old. Considering that oak trees have a long life span, diminishing production at 80 isn't unusual.
The trees that produce the most acorns are those with high canopies that allow sunlight to feed the crown causing it to produce healthy acorns, while the trees that are tucked into the forest and get limited sun produce less. Very few acorns are left after wildlife feeding and those that are produce new oak trees.
Understanding Mast Years
Some years, the acorn harvest will be extensive and throughout the region. This is called a mast year and is one of the mysteries of nature. An unusually high bumper crop of acorns happens every two to five years, resulting in thousands of acorns on the forest or lawn floor.
Wildlife is set for the winter and new oak tree growth appears when acorns germinate, but the following fall will find the supply of acorns greatly diminished. The tree spent its energy on the over-production of the acorns and needs to regroup and take a year off.