by James B. “Jim” Kea
Area Extension Agent, Forest Resources – now retired
Tuesday, February 14th, 2006
Acorns provide food for deer, bear, squirrels, mice, rabbits, foxes, raccoons, grackles, turkey, grouse, quail, blue jays, woodpeckers, and waterfowl during the critical fall and winter periods when most other good sources are scarce or not available. Understandably, populations and health of wildlife often rise and fall with acorn availability.
Generally, acorn crops are often abundant for a particular species of oak once every three or four years. White oaks were particularly abundant this year while chestnut oaks were abundant last year. This cycling is related to weather and differences in maturing times. White oak acorns take three months to mature while red oak acorns take fifteen months. White oak acorns also sprout just after falling early in the fall while red oak acorns don’t sprout until the following spring. Insects get most acorns in bad years.
Generally, larger, older trees produce more acorns. After most oaks reach 22 inches in diameter or 60 years old, production declines or levels out. Trees exposed to full sun understandably out produced shaded, under-story oaks of the same species. Acorn production varies from trees of the same species as well.
Oak stands can be managed in two ways to insure maximum acorn production. Individual trees may be favored by removing poor acorn producers or non acorn producing competition. To manage for more acorns takes several years of watching individual trees. Excellent producers will have eighteen or more white oak acorns on the last 2 feet of branch while red oaks will have twenty-four or more. Check trees about the middle of August. Thin poor producers while maintaining a good mix of species. A consistent supply of acorns is more important to wildlife than a bumper crop every other year. Good producers will generally be those that are already above the general forest canopy. Growth rates in oaks vary a great deal. An oak 12 inches in diameter may be from 20 to 120 years old.
The second management strategy involves maintaining areas of young oaks. Most oak stands in this area will begin to lose vigor and suffer disease loses after 80 to 95 years depending on soil fertility, flooding, drought, windstorms and root damage. Harvesting scattered patches of mature trees at least 4 acres in size every 10 years or so will help insure a constant supply of healthy, mature trees as well as income.
Identify potential oak sites through soil surveys. County soil surveys often list tree species growth potential for particular soil types in terms of site index. Site index is the height of the average dominant tree after fifty years of growth. A site index of 80 or better would be good. State and private nurseries have a variety of oaks available for planting. Some cost-share money is also available for planting hardwoods on the proper sites. Contact me or your local county ranger for assistance.
Revised 2/16/2006, 10/13/2011.