Florida is home to many species of oaks that vary greatly in overall size and form, longevity, and the growing conditions in which they thrive (Figure 1). Oaks grow in a variety of locations, ranging from the sandy, excessively drained soils of the Florida Sand Ridge to the poorly drained soils of alluvial bottoms. Individual oak species are adapted to different growing conditions.
There are many reasons landowners with an interest in wildlife should consider establishing or maintaining oaks on their property. The most compelling reason is that they produce acorns, which are an important food source for animals. Species such as white-tailed deer, gray squirrels, fox squirrels, flying squirrels, mice, voles, rabbits, raccoons, opossums, gray foxes, red foxes, wild hogs, wild turkey, bobwhite quail, wood ducks, mallards, woodpeckers, crows, and jays eat acorns (https://edis.ifas.ufl.edu/uw292).
Landowners can increase the survival and reproduction of many animal species by providing a steady supply of acorns (Figure 2). This is because acorns become available during the time of year when many other foods are in short supply (fall and winter). The presence of acorns can reduce food stress and increase overall animal well-being, which in turn increases their resistance to disease and parasites. Abundant acorns can reduce the amount of time animals need to search for food, decreasing vulnerability to predators. Large acorn supplies can also decrease the distance of daily animal movements and decrease the likelihood that animals will embark on long distance movements away from your property. The abundance of acorns one year can even affect the reproductive success of animals the following year.
Another reason landowners might consider planting oaks is to reduce foraging pressure on other plants. In areas where deer browsing of agricultural crops or ornamental plants is problematic, the addition of oaks may reduce the problem by providing animals with an alternative food source.
Oaks Found in Florida
See Tables 1 and 2 for a list of the oak species of Florida.
When managing oak trees for the purpose of providing benefits to wildlife, it is important to recognize that many differences exist among oak species. First, oaks of different species produce acorns that vary in nutritional quality (https://edis.ifas.ufl.edu/uw292). Second, oak species differ in the timing of acorn production, with acorns from trees in the white oak group being available for shorter periods of time than acorns from the red oak group. Third, species differ in the quantity of acorns produced (see Table 3). Finally, only those species that are adapted to the region and to the specific growing conditions of a site will thrive and produce large quantities of acorns. For these reasons it is important that landowners interested in promoting wildlife establish a variety of oak species, with representative trees that produce acorns at different times, and to plant species adapted to the conditions of the site. This will increase the likelihood that food will be available each year, that food will be available for long periods of time within each year, and that food will be available in large quantities.
Establishing New Oak Trees
Landowners and land managers with large acreages should consider retaining or establishing oaks in both bottomland and upland sites. The activity of some wildlife species, such as wood ducks, is restricted to wet lowland areas, and streamside areas in bottomlands are frequently used by many wildlife species as travel corridors. Furthermore, the rich soils characteristic of these areas tend to produce large trees, and large trees can in turn produce large acorn crops for wildlife. On the other hand, species such as squirrels and rabbits are more common in upland sites. Upland areas planted with pine monocultures generally provide limited food sources for wildlife. By providing oaks in upland areas near pine plantations, land managers introduce both food and cover options for animals.
Overall animal species diversity can be increased in an area when acorns are available in both upland and bottomland habitats. By maintaining well-distributed and abundant food and cover sources throughout their property, landowners allow animals to better meet their needs within a relatively small space. This decreases the likelihood that animals will move to adjacent properties.
Choosing the correct oak species for a site is critical to success in establishing oaks (Tables 1 and 2). Some oak species thrive in wet bottomland soils (overcup, swamp chestnut, diamond-leaf, cherrybark, shumard, and willow oak), whereas others are suited to drier, upland soils (blackjack, bluejack, Chapman, turkey, and live oaks), and still others are adapted to both bottomland and upland sites (water, southern red, post oak).
Oaks are relatively difficult to establish by artificial means but readily reproduce from stump or root sprouts. Planting seedlings is more likely to lead to successful establishment of new oaks than is sowing acorns. On dry, upland sites, use containerized planting stock. A key to obtaining good survival with oaks is to use seedlings with large stem diameters (1 inch or greater). Plant seedlings during the winter when the soil is moist. Various browse guards can be used to protect seedlings from injury resulting from animal browsing. A small amount (1/4 cup) of granular fertilizer such as 10-10-10 may be applied around the base of each seedling in early spring. Newly established oaks are sensitive to competition, so if grasses are abundant, prepare the site with an herbicide such as glyphosate (Roundup®, Accord® XRT II) in the growing season before planting. Treat a five-foot-diameter circle and mark the center where the seedling will be planted with a wire flag.
During the establishment period, which may last from 1 to 3 years, the above-ground portions of many planted seedlings tend to die back, sometimes to ground-line, while the root system is developing. This dieback often occurs during periods of dry weather or winter months (in north Florida) and is most common on upland sites. Should dieback occur, new shoots normally emerge from the green stem or root collar, and when the root system is adequate to support top growth, the seedlings will start to grow normally. Oaks grow very slowly when they are young, particularly if they are shaded.
Oaks are generally not shade-tolerant. When establishing oaks in an existing forest, seedlings should be planted where there is adequate sunlight to support their growth. Large openings in the forest canopy (50 feet across or more) caused by natural tree mortality or the intentional cutting of less desirable species make ideal planting sites. In areas where few or no oaks currently exist, establishment of approximately five oaks per acre is recommended to provide food for wildlife. Even with the best care at least five seedlings should be planted for each mature, acorn-producing oak desired, because several may die and several others may never produce large crops of acorns.
Habitat Improvement in Established Oak and Mixed Hardwood Stands
Acorn production varies not only among species of oaks, but also among trees within a single species. Healthy oaks with room to grow generally produce more acorns. In areas where oaks are present in greater densities than desired, it is wise to determine which individual trees consistently produce the greatest yield of acorns. Retain these trees and harvest the poor acorn producers. Removing the poor acorn producers will likely increase acorn production in the remaining trees.
The number of acorns a tree produces is influenced by many factors, including weather patterns, soil characteristics, density of overstory trees, the presence of disease and insects, and characteristics of the tree itself, such as age, size, crown area, and genetics. Trees should be monitored for several years to determine which consistently produce high acorn yields. Each year, use binoculars to inspect tree crowns before acorns begin to drop, and classify the trees as either above or below average acorn producers. Mark good acorn producers each year, and target for harvest only those trees that consistently produce below average yields. Individual oaks generally have large crops at irregular intervals, spanning from 2 to 10 years, so it is important to monitor acorn production for a minimum of 3 to 5 years before deciding which trees to harvest.
As a general rule, acorn yields increase as trees age, up until the point in time where portions of the trees begin to die. Also, a greater proportion of large trees produce acorns than small trees. Both of these reasons may tempt landowners to remove smaller, younger trees to hasten the growth and reduce competition for larger, older trees. It is important to remember, however, that some trees of younger age classes will be needed to replace older trees as the older ones die. If all oaks are of the same older age class, there may be a long period of time with low acorn availability when older trees have died and younger trees are not yet producing good crops.
Some oaks respond positively to fertilization, whereas others do not. Fertilization may increase diameter or height growth, and under certain conditions it may increase acorn production. However, the response of individual trees to fertilization is variable, so time and money is probably better spent on other habitat improvements rather than on oak fertilization.
Most native oaks do not begin producing significant acorn crops until they reach about 20 years of age. Therefore, oak management should be viewed as a long-term investment in habitat improvement for wildlife. Sawtooth oak (Quercus acutissima), a non-native species originally from Asia, was once recommended to landowners interested in increasing mast availability in the southeastern United States because it produces acorns at a much younger age than most oak species native to the region. However, given the short period of availability of acorns from this exotic species and the multitude of native oak species available in Florida, planting a variety of native species of oaks is considered a superior alternative to planting sawtooth oaks.
Additional information
Byrd, N. A. and H. L. Holbrook. (1974). How to improve forest game habitat. Forest Management Bulletin. USDA Forest Service, 1720 Peachtree Road, NW, Atlanta, GA 30309. 6 pp.
Demers, C. Long, A., and Latt, C. (2011). Establishing and maintaining wildlife food sources. SS-FOR-12. Gainesville: University of Florida Institute of Food and Agricultural Sciences. https://edis.ifas.ufl.edu/fr062
McShea, W. J., and Healy, W. H. (2002). Oak Forest Ecosystems: Ecology and Management for Wildlife. John Hopkins University Press, Baltimore, MD.
Ober, H. K. The value of oaks to wildlife. (2000). WEC248. Gainesville: University of Florida Institute of Food and Agricultural Sciences. https://edis.ifas.ufl.edu/uw292
Schaefer, J.M., Cohen, J. and Hostetler, M. (2015) The wood duck. WEC168. Gainesville: University of Florida Institute of Food and Agricultural Sciences. https://edis.ifas.ufl.edu/uw180
Sekerak, C.M., and Tanner, G.W. (2014) Making the most of your mast. Gainesville: University of Florida Institute of Food and Agricultural Sciences. https://edis.ifas.ufl.edu/fr036