Post Oaks: The signature tree of Milam CountyThey make great fence posts, railroad ties, and planking. Its other name is “iron oak” because the wood is heavy and coarse-grained.
The Post Oak is native to Texas, and can be found throughout the state. However, it’s most prominent in the aptly named “Post Oak Savannah.” It is one of the most drought-tolerant oaks. It prefers rocky or sandy areas, and is a popular choice in urban areas for stabilizing sloping sites since it grows where a lot of trees won’t.
Wildlife uses all parts of the Post Oak. Its acorns provide food for wild turkey, whitetailed deer, squirrels, and other animals during the fall and winter. The leaves are used for nests, and the cavities and stumps from dead trees are used as homes for various animals. However, the tannin from the leaves, buds, and acorns can be toxic to domesticated livestock.
Thirty-seven butterfly and moth species use the Post Oak as a larval host plant, including the Red Spotted Purple butterfly, Banded Hairstreak butterfly, and Juvenal’s Duskywing butterfly.
Native Americans also ate the acorns. Medicinally, they used it to treat fevers, dysentery, and skin infections.
The Post Oak is a long-lived tree, and is rather small compared to other oaks. It averages a height of 30 to 50 feet, but can grow up to 75 feet tall. Its trunk can grow two feet in diameter. It has a dense, oval crown with thick gray to reddish brown bark that looks like scales.
The leaves of the Post Oak have a leathery look, with seven rounded lobes. The middle lobes are longer and perpendicular, which gives the leaf a cross shape.
Post Oaks have both male and female flowers. The male flowers are yellow-green hanging catkins. Female flowers grow at the leaf base, and are reddishbrown spikes. They begin producing acorns when they reach 25. This is typical for most oaks. Acorns range from 3 .4 inches to one inch long. They can germinate immediately after they drop from the tree in the fall.
If you want to grow your own Post Oaks, pick them directly from the tree when they have turned brown. Plant them immediately in the ground, or in pots, as they don’t last long in storage.
Post Oaks grow alongside Blackjack Oak and Yaupon. Dogwoods often grow under their protective shade. Much of the research suggests Post Oaks are intolerant of competition, as well as shade. This may be true, but like most things in nature, the “rules” serve mainly as guidelines. I know on my own property, I’ve seen many a Post Oak do just fine surrounded by tangles of Yaupon, Blackjack, and a variety of other vegetation.
Be careful, however, when landscaping or building around mature trees. Their roots grow close to the ground, and are sensitive to disturbance. Running heavy equipment over the root zone, or paving over it, can kill it. When landscaping around the tree, changes in soil levels and overwatering can kill it.
With all the frigid weather we’ve had, consider a Cherokee custom. They would burn a fire of Post Oak and grapevine to bring a spell of warm weather during the winter.
The Master Naturalists are looking for the largest Post Oak in Milam County. To nominate a tree:
Download a form from the website: http://grovesite.com/ tmn/ecrmn/bigtrees, or pick up a hardcopy at the Extension Office in Cameron.
Mail forms to: El Camino Real Master Naturalist, c/o AgriLife Extension Service, 100 E. First St., Cameron, 76520; or email to MilamMasterNaturalist @gmail.com.