22. Quercus stellata Wangenh. (post oak)

Pl. 416 f, g; Map 1860

Plants trees, 3–20 m tall. Bark light gray, divided into loose or more or less persistent ridges or blocks. Twigs (2.5–)3.0–4.0 mm wide, whitish tan or gray, densely felted with small, stellate and branched, spreading hairs. Buds reddish brown, 4–6 mm long, the scales pubescent (the inner scales only sparsely so), hairy along the margins. Petioles 10–20 mm long. Leaf blades 12.5–20.0 cm long, 9–15 cm wide, relatively thick and rigid, obtuse to truncate at the base, divided 70–90% of the width, the lobes 2 or 3 per side, the largest lobes usually near the tip; well-developed lobes (29–)37–72 mm wide, with 1 secondary lobe as large as the main lobe on the lower margin, truncate or notched to 2-lobed apically; secondary veins 2–6 per side, some reaching the margin at the tips of the lobes, others reaching toward sinuses and turning aside before reaching the margin; the upper surface more or less shiny, with scattered, 4–10-rayed, spreading hairs, the undersurface green, with scattered, erect, 4–11-rayed hairs and few to many, white or orange, appressed unbranched hairs, harsh-felty or almost sandpapery to the touch. Acorn stalks absent or to 8 mm long, the cup 6–11 mm long, 12–16 mm wide, covering 50–70% of the nut, hemispheric, the outer surface with the scales 1.5–2.5 mm long, those near the cup margin not differentiated. Nuts 12–13 mm long, 8–12 mm wide, ellipsoid to barrel-shaped. April–May.

Scattered to common nearly throughout the state (eastern U.S. west to Iowa, Kansas, and Texas). Mesic to dry upland forests, glades, upland prairies, tops of bluffs, margins of sinkhole ponds, and banks of streams; also pastures and roadsides.

Steyermark (1963) reported the sand post oak, Q. margarettiae (Ashe) Small (Q. stellata var. margarettiae (Ashe) Sarg.; Pl. 417 a), from southwestern Missouri based on a few historical collections from Jasper and Lawrence Counties. Most of these represent merely depauperate plants of Q. stellata. However, the one Lawrence County specimen for which he cited collection data (Palmer 51154, at the University of Missouri Herbarium) appears to represent the hybrid, Q. prinoides × Q. stellata, or possibly a backcross between this hybrid and Q. stellata. Quercus margarettiae (often spelled Q. margaretta in the botanical literature) is a small tree mostly confined to loose, sandy soil. It resembles Q. stellata, but differs in lacking stellate hairs on the twigs (its twigs are usually glabrous but sometimes have scattered large, branched spreading hairs), and in having the hairs of the leaves stalked. It has not been documented to occur north of central Arkansas. To date, Q. stellata has been documented to hybridize with four other oak species in Missouri.

In 2012, late in the preparation of the present treatment, Justin Thomas collected a specimen of an unusual post oak from Otter Slough Conservation Area (Stoddard County) and subsequently located a few older herbarium records of similar trees from adjacent portions of the Mississippi Lowlands Division. These are morphologically identifiable with specimens from the southeastern United States that have been called Delta post oak or swamp post oak (Q. similis Ashe). Quercus similis differs most notably from typical Q. stellata in that it occurs in bottomland forests and swamps, where it forms canopy trees to 25 m tall. Its leaves also differ somewhat from those of typical post oak in their sometimes narrower outline and more irregular pattern of lobing (often with some of the blades more shallowly lobed or merely 3-lobed at the tip), as well as the somewhat narrower angle of branching of the secondary veins going into the largest lobes. However, the taxonomy of Q. similis presently is not well-understood and further research needs to be conducted to determine whether it represents a valid species, a hybrid between Q. stellata and some other oak, or an ecological variant of Q. stellata. The status and characteristics of this entity in southeastern Missouri also need to be assessed through more detailed field observations.