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How to maximize acorns

Tree Talk: Keep your wildlife well-fed with these tips for improving tree mast production.

Oak trees are valuable not only for the lumber but also for the acorns, too — as a valuable foodstuff for deer, turkey and other wildlife. So valuable are these byproducts, they even have their own name: mast. How can you manage woodlands for better mast production?

All flowering woody plants produce some type of fruit, and mast can be an important year-round food source for many animals. Mast can be classified as either hard or soft.

Hard mast refers to hard-shelled seeds that can be stored for long periods and are high in fat, carbohydrates and protein. Because of its high energy content, hard mast is a very important nutritious winter food when other food sources are limited or nonexistent. Acorns, hazelnuts, hickory nuts, beechnuts and walnuts are good examples of hard mast.

In contrast, soft mast consists of fleshy, perishable fruit that is high in sugar, vitamins and carbohydrates. Soft mast is usually not readily available to wildlife during the winter but is a very important energy source when animals are migrating. Soft mast includes black cherry, persimmon, pawpaw and blackberry. Interestingly, many of these same soft-mast foods were important sources of food for humans and are making a comeback.

Oak trees are monoecious, meaning “one house,” with female and male flowers on the same tree. But neighboring trees are cross-pollinated by wind. Male flowers consist of catkins, and female flowers are short, rounded to pointed spikes on the leaf axils. Acorns are produced at the end of twigs. Oaks prefer to grow in full sunlight, so dominant and co-dominant trees are the best acorn producers. Large trees typically produce more fruit than smaller trees.

It takes about 30 years of growth before an oak tree bears acorns, and production can be quite variable depending on tree species, pollination, weather and insects. Research has shown that most oak species produce a good acorn crop one year out of three or four. Additionally, studies have shown that only about 30% of large, healthy trees will produce acorns even in a good year; and as a group, white oaks tend to be more consistent than red oaks.

How to manage

Like any forest resource, acorn production requires some management. Acorn production can be assessed by examining trees in September while hunting, hiking or camping. Make notes of trees that produce in an off-year. Generally, these trees will be your best producers and should be retained and managed. Mid- to late August is the optimum time to observe and evaluate trees for acorn production — before they are consumed by the critters.

Thinning practices around good acorn producers will help open up the crowns to full sunlight, as well as provide better growing conditions and more efficient acorn production. Try to keep a mix of both red and white oak species so as to minimize the year-to-year fluctuations in acorn production. Suggested ratios of oaks would be 2 to 1 or 3 to 1 red oaks to white oaks; this will help avoid a total annual mast production failure.

When selecting which trees to keep, be sure to consider tree diameter. Acorn production in northern red oak generally peaks when the diameter at breast height reaches 20 inches, while white oak reaches maximizes acorn production at around 26 inches.

Other hard mast producers include birch, hickory, pine, black walnut, hornbeam, dogwood and hophornbeam. Soft mast producers include persimmon, black cherry, hackberry, mulberry, plum and pawpaw.

Keep in mind that tree diversity is the key in providing a good variety of wildlife foods for both the summer and winter months.

Miller is a horticulture professor at Joliet Junior College and a senior research scientist in entomology at The Morton Arboretum in Lisle, Ill. Email your tree questions to him at

The opinions of this writer are not necessarily those of Farm Progress/Informa.


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