Anyone who has kept livestock knows the value of having a good fence, and the work required to keep one up. The effort and expense of replacing rotting posts is a pain. I once saw my uncle laugh at the idea of putting weather caps on the top of posts to help prevent rotting. He said he never saw a post rot from the top. Moisture does wick through posts by capillary action and promotes rot, but I think he was right- a post usually takes in most of its moisture from the ground. An ideal post’s xylem and phloem channels would somehow not wick water from any source, and the wood would be strong, hard, heavy and durable. These qualities actually describe the post oak, Quercus stellate, a tree whose common name is derived from its most ideal use.
The scientific name of the post oak, stellate, means star-shaped. This describes the tiny trichome hairs on the leaf underside, which branch in a star-shaped pattern. The function of these hairs is unknown, but the tree values drought tolerance. The hairs could help this by cutting down on air flow across the surface, limiting moisture loss. They could shade the surface to retard moisture evaporation. Possibly, they could help attract moisture to the leaf in fog.
The post oak, Quercus stellate, grows throughout the southeastern and central United States, often abundantly. It ranges from southeastern New York to central Florida, and westward to central Texas and Nebraska. Though it grows in moist and well-drained, sandy or loamy soils, it is also very 
drought tolerant and very intolerant to flooding. It is typically found on rocky or sandy ridges and in dry woodlands. This rugged tree usually grows to be a small- to medium-sized tree, averaging 30 to 50 feet tall, but many reach heights of 75 feet. It often takes 10 years to grow 2 inches in trunk diameter, which is slower than most other oaks. A mature tree’s spread is often wider than the tree’s height, as seen in the Champion post oak in Atlanta, Georgia. This tree is 93.4 feet tall, with a spread of 96.0 feet and trunk circumference of 11.9 feet. Post oaks have a long lifetime, as evidenced by a tree in Oklahoma that Virginia Tech found to have lived 373 years. The Arkansas Tree-ring Laboratory has found post oaks as old as 400 years.
Post oaks share many traits with the white oak grouping of oaks. They have scaly and gray to light reddish-brown bark, which becomes thick and blocky with shallow fissures and scaly ridges. The fissures and ridges of older trees appear to twist slightly down the trunk’s length. The crown is broad, dense and dome-shaped. Branches are strong, thick and spreading, and sometimes they are contorted. Twigs are gray, thick, and dotted with lenticels. They are densely covered with yellowish, star-shaped hairs most of the year. The tree has a tap root, which makes it difficult to transplant. Surface roots are not usually a problem, but the root system is very sensitive to disturbance.
The post oak is one of the last trees to leaf out in spring. Leaves are simple and alternate, attached to ½ inch long petioles or leaf stalks that are thick and stiff. Leaf bases my be rounded or wedge-shaped. Main leaf veins end in lobe leaf edges without bristles. Three smooth lobes make a shape much like a maltese cross, and in some areas there could be two much smaller lobes at the base and the end lobe could have 3 notches. Leaves are usually 4 to 6 inches long and as broad, and are thick and somewhat leathery. They are dark green and shiny on the upper surface, and brownish-green with fine hairs underneath. Autumn leaf color is yellow to brown.
Acorns are formed from pollinated female flowers. Flowers of both sexes are found on the same tree in April to May, just as the leaves begin 
to emerge. Male flowers are 2- to 4-inch long yellow catkins that grow in drooping clusters. Female flowers are red, appear as short spikes, and are inconspicuous. The acorns are usually light brown, occur singly or in pairs, and are up to 1 inch long. Each one has a reddish-brown cap covering about 1/3 of its length, having slightly hairy flat scales but no fringe. The cap is attached to twigs by short stalks. Acorns mature in one year, and when they fall in autumn they germinate and sprout before winter, if possible. Post oaks begin to bear acorns at about 25 years of age.
The post oak has often been called ‘iron oak’, because the wood is hard, heavy, strong and durable. It is resistant to decay when in contact with soil, because tyloses plug transport channels in the wood preventing wicking of water. Post oaks have had much use as fence posts. Larger trees are cut into lumber and used for rough construction, railroad ties and mine props, but not finished lumber. It is burned as fuel. Native Americans have processed the acorns to eat, and used bark medicinally to treat dysentery, fevers, skin infections, and canker sores. Acorns are an important source of food for deer, small animals such as squirrels, and birds such as turkeys. When used as shade trees, surface roots are not a problem. However, the tap root makes transplanting difficult and they grow slowly.
The post oak is common in the Atlanta area, but because it is not carried in the nursery trade, it is often ignored. As it is easy to identify and its nature and uses are interesting, the post oak should not be overlooked.
Post oaks in Central Mississippi are a favorite host for Spanish Moss.
It helps conserve water in dry conditions. This is a tough tree.
Why is the top side of the leaf glossy?