Oaks May be Impacted by Heat, Drought
FRANKFORT, Ky. – Oaks are the most important tree species to wildlife in Kentucky forests, but the impact of this year’s drought remains to be seen. White oaks are faring better than red oaks so far.
White oaks produce acorns that are a critical food source for squirrels, white-tailed deer, wild turkey, black bear and many non-game species. White oak acorns are preferred by wildlife because they are more palatable. Acorns produced by red oaks contain tannin, which makes them bitter.
White oaks can produce acorns every year. Entire crops are often lost due to late freezes and heavy rains just as pollination of oak flowers begins as well as summer droughts.
Philip Sharp, a private lands wildlife biologist for the Kentucky Department of Fish and Wildlife Resources in Crittenden County, said it’s too soon to make a prediction on the mast crop in western Kentucky, the area of the state most affected by drought. “Our white oaks have small acorns now, but that’s pretty typical for this time of year. They can grow a lot in a short period of time and fill out in late summer.”
Red oaks are not faring as well. “Some areas of western Kentucky are really dry. There are places that have had about a half inch of rain in the past two months,” said Sharp. “I’m concerned. The dry conditions are killing some of our red oak trees on ridges with thin soils.”
According to the U.S. Drought Monitor, Crittenden and parts of nine other Kentucky counties along the lower Ohio River are classified as being in an Exceptional Drought, the driest category of five listed. Because it takes two years for red oak acorns to mature, and not all trees produce mature acorns in the same year, red oaks are a more reliable source of acorns on an annual basis.
David Yancy, senior deer biologist for the Kentucky Fish and Wildlife, said a mix of white and red oak species is preferred. “This will ensure that some acorns will be there for wildlife when there’s a failure of the white oak crop.”
According to the University of Kentucky Cooperative Extension Service, there are 10 native species of oak trees in Kentucky: six members of the red oak group and four of the white oak group.
Typically, it takes an oak tree about 20 years to start producing acorns.
The U.S. Forest Service’s 1981 Wildlife Habitat Management Handbook said the white oak (Quercus alba) followed by the chestnut oak are the two white oak species in Kentucky that produce the highest yields of acorns. For red oaks, it’s the northern red oak (Quercus rubra), then the scarlet oak (Quercus coccinea).
The leaves are a good way to tell the difference between white oaks and red oaks. White oak leaves are narrower (about 4 inches) with rounded lobes. Red oak leaves are wider (as wide as 6 inches) with pointed lobes.
Although oaks are considered intermediate in their tolerance to shade, they grow best on sites with openings in the forest canopy and minimal competition for sunlight, water and nutrients from other plants. Oak stands regenerate naturally by sprouting acorns as well as stump sprouts.
Since acorns and other hard mast are so important to wildlife, department biologists began an annual survey in 1953 to assess each year’s crop. Biologists walk the same route every year and determine the proportion of trees bearing hard mast by observing nuts on hickories, white and red oak and beech trees.
The mast survey helps biologists predict game availability and behavior. For example, each year’s estimate of the number of squirrels available to hunters is based on the previous year’s mast crop.
In years when the mast crop is sparse, deer and wild turkey are more vulnerable to hunters because game must move around more to find food. In years of plenty, deer and turkey harvests are likely to decrease because food sources are available everywhere, so there isn’t as much game movement.
Nuts begin to mature in mid-September. The annual survey will be conducted this year between Aug. 15 and Sept. 1.
The Kentucky Department of Fish and Wildlife Resources manages, regulates, enforces and promotes responsible use of all fish and wildlife species, their habitats, public wildlife areas and waterways for the benefit of those resources and for public enjoyment. Kentucky Fish and Wildlife is an agency of the Tourism, Arts and Heritage Cabinet. For more information on the department, visit our website