Tree of the Week: Post Oak (Quercus stellata)

We have had several weeks of hot weather with little rain and we see little change in the forecast. Daily high temperatures are predicted to be in the mid to upper 90s. In preparation for this onset of summer, the arboretum's irrigation system has been in full operation. Our native azaleas and oak-leaf hydrangeas seem to be the most sensitive to the heat: their leaves are the first to droop. But most of the plants in the arboretum so far show no sign of stress. This is a big advantage to planting native trees: natural tolerance to conditions means less worry. Last week we studied the short-leaf pine (Pinus echinata), which is described in the literature as moderately drought tolerant. This week, let's look at the post oak (Quercus stellata), a tree that prefers dry conditions.

The post oak is a natural for Shreveport and the Centenary College campus. Northwest Louisiana is located in the piney woods ecoregion that can be found across east Texas; post oaks are a defining species for this region. When the first arboretum plantings were made in the spring of 1985, there were numerous pre-existing post oaks across the campus and in the arboretum. Over the years, the population has dwindled due to oak wilt and lack of recruitment. Eleven trees died between 1985 and 2003. Several more followed. Today, there are three large on-site natives remaining in the arboretum collection. These are massive trees, with the leaves way up out of reach. Luckily, we also have a small tree to study. In 2000, Professor Ed Leuck planted a seedling from campus seed. You can find it in full sun, at the top of the grassy slope outside of Cline Hall dormitory.

This little tree is 18 years old. Post oaks are slow-growing trees, which might be considered a mark against this species; however, the slow-growing nature of the tree may be what allows it to become drought resistant.

This post oak is growing in full sun, in clay soil, at the top of a grassy hill outside of Cline Hall (pictured).

Post oaks are in the white oak group. They have simple, lobed leaves.

Leaves alternate along the stem.

A typical post oak leaf is symmetrically lobed with a cruciform shape.

But there are plenty of interesting asymmeterical shapes as well.

The post oak leaf is pale green underneath.

The underside of the leaf feels fuzzy.

We missed seeing the flowers, but we definitely see acorns developing.

The rough, gray bark divides into irregular scales.

A dragonfly was found perched on the post oak in the heat of the day.

We have a female blue dasher dragonfly (Pachydiplax longipennis). Thanks to Bob Thomas for his article, Dragonfly Swarms: A Summer Delight.

You can see pictures of the arboretum's older post oaks here.

For more information about this species consult the following:
United States Department of Agriculture
Virginia Tech Dendrology
U.S. Forest Service