A comprehensive database of Tennessee native plants
Post Oak, Iron Oak
Full sun; medium to dry moisture level; grows best in rich organic loam but will grow in rocky, sandy, sandy loam or clay loam; strongly acid to slightly acid pH.
35-50 feet height by 35-50 feet spread; blooms in spring when leaves emerge with yellow-green, drooping male and female catkins, 3-4 inches long; light brown or nearly black, dome-shaped acorns, ½ – ¾ inch long, in fall. Acorns mature in one season.
Growth Rate: Slow
Maintenance: All oaks are susceptible to a large number of diseases, including oak wilt, oak leaf blister, cankers, leaf spots and powdery mildew. Potential insect pests including scale, oak skeletonizer, leaf miner, oak lace bugs, borers, caterpillars and nut weevils. Notwithstanding these problems, oaks are generally considered to be low maintenance trees.
Propagation: Seed germination code A. Due to a deep, extra thick taproot, best to simply plant an acorn directly in ground or do container-grown seedlings in deep containers for no more than 1-2 years.
Native Region: Statewide
Medium sized oak with a dense, oval crown and stout, spreading branches. This is a variable tree with great variation in leaf, bark and growth habit. Generally appears as a scrubby tree but can occasionally get pretty large on better growing sites. Reaches its greatest size on silty loam soils where it can become a beautiful shade tree. Fall color is variable, ranging from uninteresting to attractive shades of yellow and brown. Not often used in landscape situations but frequently found in the wild throughout southeast and south central U.S. Occurs naturally on dry, rocky ridges, prairie edges and poor upland forests. Drought resistant and can be planted for soil stabilization on dry, sloping, stony sites where few other trees will grow. Roots extremely sensitive to disturbance and does not tolerate soil compaction or soil removal for development. Called post oak because its durable wood has been used for fence pots. Begins to bear acorns at about 25 years of age, and good crops are produced every 2-3 years.
Very high wildlife value. Acorns provide food for songbirds, game birds, deer and small mammals. Nesting site for birds. Attracts butterflies. Larval host for Northern Hairstreak and Horaces Duskywing butterflies.