Fall 2018 Conservationist

Nuts About Oaks

by Scott Meister, Natural Resources

Whenever someone asks me, “How can I attract more wildlife to my backyard?” my response is always the same: “Plant an oak!”

Many homeowners avoid planting these stately trees because they think they’re slow-growing, but some oaks, such as the northern red oak, can grow more than 2 feet per year. More important than growth rate (especially if you’re a squirrel or woodpecker) is the value oaks hold for wildlife, which exceeds that of many trees.

Although nicknamed the Prairie State, Illinois was nearly 38 percent woodland prior to European settlement. Many of these areas were dominated by oaks, which kick-started wildlife’s centuries-long dependency on the trees for food and shelter.

Packed with fats and carbohydrates, oak acorns are an appealing source of much-needed nutrition for more than 100 species of wildlife, including white-tailed deer, turkeys, blue jays and squirrels. According to one study, wildlife can eat up to 83 percent of an oak’s acorn crop.

But not all acorns are created equal — or eaten equally in fall and spring. Oaks belong to one of two groups: white (white, swamp white, bur, chinquapin) and red (northern red, pin, black). Of the two, white oak acorns have fewer tannins. This makes them more palatable (and preferable) to wildlife. White oak acorns also germinate more quickly, which means they start to convert their fats and carbohydrates into sprouts earlier in the growing season. As a result, animals may eat a mix of white and red in fall, but in spring, when many of the tastier white oak acorns have already been consumed and those that remain are starting to sprout, animals may rely more on red.

Migrating songbirds are another guild that depends on oaks for food, although not for the acorns. Over 500 species of insects live and feed on oaks; other widely planted trees only support a handful. Because of this disparity, you’re more likely to attract migrating birds to your yard with oaks than, say, maples. Oaks’ catered bug buffets allow Wilson’s warblers, American redstarts, common yellowthroats and other migrants to find food faster, saving time and energy for their long journeys ahead.

In addition to being a critical source of food, oak trees offer valuable shelter. Natural cavities can form in any tree, but larger species, oaks included, can support larger cavities without detriment to the trees themselves. This means more sizes and species of wildlife are able to claim squatter’s rights. Red-headed woodpeckers, identified as in greatest need of conservation by the Illinois Wildlife Action Plan, rely on cavities to raise their young as do eastern bluebirds and southern flying squirrels. Because they all readily nest in oaks, adding oaks to your yard can make all three great additions to your wildlife watch list.

Even an oak tree’s leaves are superior when it comes to habitat. Leaves on deciduous trees “senesce” in fall, which means they die and dry up. On many trees the leaves soon drop, but the browning leaves on some oaks remain on the branches through winter. This gives smaller tree-dwelling creatures cover from predators at a time when cover is scarce. When an oak does drop it leaves, they decay more slowly and remain in the environment longer than others, creating protected areas for mice, snakes, insects and other animals that shelter on the ground.


Because oak leaves take longer to decay than those from other trees, they provide valuable cover and camouflage for ground-dwelling animals, such as American toads. Image by Will Parson/CC BY NC 2.0

There’s a Greek proverb that states, “A society grows great when old men plant trees whose shade they know they shall never sit in.” Planting an oak tree in your backyard will not only enrich your quality of life today but also welcome and maintain healthy populations of wildlife for years to come.

oak-iStockcomSnajpoFrom Acorn to Oak in Your Own Backyard

Know someone with an oak tree? Ask for some acorns and then follow these steps to grow your own! (Remember, collecting anything plant-related in a forest preserve isn’t allowed.)

1. Select healthy acorns. 

In fall, choose acorns that have recently fallen or are easy to pick.

2. Perform a float test.

Place the acorns in water for at least an hour. Discard any that float; they won’t grow. Dry off any that sank.

3. “Stratify.”

Acorns need a period of cold, moist dormancy called “stratification” to germinate. To stratify yours, place them in a sealed plastic bag with moistened peat, vermiculite, sawdust or similar materials. Keep the bag in a refrigerator for at least 40 days.

4. Monitor.

Periodically check your acorns. Keep the material around them moist but not too wet, and don’t allow it to dry out. Roots may emerge after 40 days, but even if they don’t you can still move to the next step.

5. Place in pots.

For each acorn, fill a well-draining pot with soil and plant the acorn an inch below the surface. Put the pot indoors by a south-facing window so it gets the warm winter sun.

6. Wait and then plant!

Keep the soil moist and don’t let it dry out. In a few weeks, you should start to see growth above the surface. In spring after any chance of frost has passed, you can plant your young oaks outside. Image iStock.com/Snajpo