Once you have identified the best acorn producers in the stand it is time to conduct a timber harvest to improve acorn production of those trees. The efforts you have taken with your acorn survey, combined with the following guidelines will encourage consistent, abundant acorn crops from your oak stands and allow you to meet my suggested minimum of 200 pounds of acorns per acre needed to meet the needs of a variety of wildlife on your property.
Consult a forestry professional
The first step in any timber harvesting operation is to consult a forestry professional to help you prepare and oversee your timber harvest. If managed correctly, your oak stands should pay for themselves and help offset the cost of other management projects on your property. Ask your state Cooperative Extension Forestry Specialist or your State Forester to visit your property and provide you with a list of the consulting foresters in your area. Use the following recommendations to educate yourself regarding the approach your forester should be taking when they plan the harvest in your oak stand.
Release marked oaks
Now that you have identified your best acorn producers, the first step should be to provide those trees with growing room. Have your forester remove any poor producers whose crowns are touching the crowns of your marked trees. Ideally, you want competing trees removed from at least three sides of your best producers. If done correctly, your stands will need this treatment only once every 12 to 15 years; as soon as the crowns of neighboring trees start touching again, it will be time for another harvest.
While you want the top ½ of the crowns of your best trees exposed to sunlight, you don't want the trunks exposed to light because they will sprout. Trunk sprouts or "epicormic branches" can significantly reduce the timber value of your trees. One good way to avoid opening up your stands too much is to leave suppressed trees and understory shrubs uncut; these trees aren't competing with dominant and co-dominant trees, and they help shade the trunks of your bigger trees.
Maintain good species diversity
Work to maintain a diversity of oak species on your property. A good guideline is to manage your oak stands to be comprised of one "White Oak" for every three "Red Oaks" (1:3). "Red Oaks" are more consistent producers than "White Oaks" and having the two groups of species in the same stand will buffer against a total crop failure if one group doesn't produce acorns. Also, retain other mast-producing species such as American beech. These trees provide deer with another food source and further buffer against poor acorn crop years.
Allow oaks to attain proper age
To maximize acorn production, at least half of your oak stands should be comprised of trees greater than 50 years old. Work to have this age-class distributed evenly across your forested acreage. Locate younger stands directly next to +50-year-old stands to provide browse and cover opportunities to your deer.
Allow oaks to attain proper diameter
Allow your best acorn producers to grow larger than 20" in diameter, as most oak species begin producing their largest crops at this size. Periodically thinning around these trees every 12 to 15 years will encourage good acorn production for many years. Don't let anyone talk you into a timber harvest where all trees over a certain diameter will be harvested. Such "diameter-limit" cuts will reduce acorn production and can significantly reduce the quality and health of your oak stands. Conduct your acorn surveys prior to each timber sale to determine when a large diameter tree is no longer producing large crops consistently.
Basal area guidelines
Foresters use basal area as a guide to determine the correct distribution of trees needed to meet your management objectives. The best acorn production will be achieved in stands where basal area is between 60 and 100 square feet per acre and oaks average greater than 20" dbh.
I suggest that your forester use the larger basal area because it allows you to retain a few more trees per acre; this provides insurance for those times when a tree you've identified as a "good producer" turns out to be not so good after all. The concept of basal area isn't difficult, but it is best taught in the field; ask your forester to show you how to measure the basal area of your forest stands.
Don't fertilize oaks growing in your forest
Fertilize your food plots, not your forest. Don't waste your time and money trying to fertilize oaks to increase acorn production. Although there is some competition between trees for water and nutrients, sunlight is by far the most important resource your trees need for growing large acorn crops. Acorn production is so variable from year to year, it's difficult to prove that fertilizer is responsible for any change you observe in your acorn crop. Thinning your oaks is a much more effective way to provide your trees with the resources they need to produce acorns. Take what time you had set aside for fertilizing oaks and use it to conduct the acorn survey.
Conclusion
If you follow the survey and management guidelines I present in this series of articles you will be rewarded with improved acorn production and growth from your oaks. Additionally, the timber sale will increase sunlight into your forest and stimulate the growth of stump sprouts and oak seedlings; those not eaten by deer can be nurtured into your future oak stand. Money you generate from the timber sale can be used to pay for other habitat improvement projects, or to have your next acorn-fed trophy mounted!
Greenberg, C. H. 2000. Individual variation in acorn production by five species of southern Appalachian oaks. Forest Ecology and Management. 132:199-210.
Greenberg, C. H., and B. R. Parresol. 2000. Acorn production characteristics of southern Appalachian oaks: a simple method to predict within-year acorn crop size. Res. Pap. SRS-20. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 14p.
Healy, W. M. 1997. Thinning New England oak stands to enhance acorn production. N. J. of Applied Forestry. 14:152-156.
Healy, W. M., A. M. Lewis, and E. F. Boose. 1999. Variation of red oak acorn production. Forest Ecology and management. 116: 1-11.
Johnson, P. S. 1994. How to manage oak forests for acorn production. TB-NC-1. USDA Forest Service. North Central Forest Experiment Station 4 pp.
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Perry, R. W. 1999. Estimating mast production: an evaluation of visual surveys and comparison with seed traps using white oaks. Southern J. Applied Forestry. 23:164-169.
Sharp, W. M. 1958. Evaluating mast yields in the oaks. Bull. 635. University Park, PA: Pennsylvania State University, College of Agriculture, Agriculture Experiment Station. 22pp.
Seeds of Woody Plants in the United States. 1974. C. S. Schopmeyer Tech. Coordinator. Agricultural Handbook No. 450. USDA. Washington, D.C. 883 pp.
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