Chinkapin Oak is a medium size to large native deciduous tree, growing 50 to 80 feet in height and 2 to 3 feet in diameter, with slightly narrow but rounded crown. It can also be shrubby in certain environments.
Bark is thin, light gray, scaly and shallowly fissured on older trunks.
Twigs are reddish-brown turning gray in the 2nd year, of slender to moderate stoutness, white dotted, with sparse fine hair in the green stage initially which is then lost. Buds are brown to reddish-brown, almost round to ovoid appearing above the leaf scars. Lateral buds are held tight against the twig while there will be multiple small rounded terminal buds, also reddish-brown which may have some fine hair on the scales.
Leaves: Leaves occur only on the current years twigs and are obovate to oblong in shape, up to 7 inches long and half as wide, widest just above the middle, with a dark green leathery upper surface and a much paler underside. Leaf margins undulate with either teeth or shallow lobes, the teeth or lobes rounded or more acutely upward pointed. Sinuses are lacking. Leaf bases are truncate to cuenate (wedge-shaped). Secondary leaf veins usually number 10 to 14. The underside of the leaf lacks tufts of straight hairs found in some other oaks but can have appressed stellate hairs.
Flowers: The tree is monoecious, that is with separate male and female flowers. The male flowers develop as hanging catkins from the leaf buds of leaf axils of last years' growth. Female flowers form from the leaf axils of the current years growth. They are very short and greenish-red in color, and appear with the leaves.
Seed: The female flowers mature to a round, elongated acorn, 1/2 to 1 inch long, 1/4 to 1/2 enclosed in a thin bowl-shaped cap with tightly pressed brown scales tapering to either a very short stalked base or no stalk at all. The scales usually have short gray hair. The nut is light-brown at maturity. They appear either singly or in pairs. The acorn matures in the first year - as do most species in the Quercus Sect. Quercus - the White Oak Group.
Habitat: Chinkapin Oak is one of the most widespread species of trees in temperate North America. It is found in mixed deciduous forests, usually on slopes and in areas of limestone and calcareous soils. It can be found in riparian habitats in western North America. It may hybridize with other Oak species. Shrubby versions do not produce acorns.
Names: The genus name, Quercus, is the Latin word for Oak. The species, muehlenbergii, is an honorary for Gotthilf Heinrich Ernst Muhlenberg (1753-1815) American Botanist who produced several catalogues of plants after retiring as a Lutheran pastor. The author name for the plant classification - ‘Engelm.’ refers to George Engelmann (1809-1884), German-American botanist. Educated in Germany, he came to the U.S. in 1832, undertaking many land exploratory trips of behalf of his uncles in Germany. His botanical notes formed the basis for a number of studies of plants in western North America. While he earned his living as a medical doctor in St. Louis, his work on Phylloxera proved the savior of the French wine industry in 1870s. The Engelmann Spruce is named for him.
Comparisons: Chinkapin Oak in shrub form resembles Q. prinoides, the Scrub Chestnut Oak, but that species produces acorns on small shrubs and spreads clonally which Q. muehlenbergii does not. As a large tree there is a resemblance to Q. bicolor, the Swamp White Oak, but the leaves of that tree have sinuses and blunt tipped lobes.
Below: Twigs are reddish brown initially with white lenticels. Buds are brown to reddish-brown. Lateral buds are tight against the twing, terminal buds are clustered - small and round. 3rd photo - old bark is shallowly fissured.
Below: Leaf margins are lobed or with rounded to pointed tooth. Indentations are shallow - no sinuses. The underside is much paler in color without tufts of hair at the veins.
Below: Leaves form on new twigs only, in a cluster. The upper surface is a glossy leathery green. Fall color is brown.
Below: 1st photo - the male catkins, prior to the flowers opening. 2nd photo - new acorns forming. 3rd photo - mature acorn, photo ©Gary Fewless, University of Wisconsin.
Notes: Chinkapin Oak is found in the United States from the Great Plains eastward excepting upper New England. In Canada, only Ontario has reported it. It is historical in Minnesota with the last known specimen collected in Houston County in 1899. South-eastern Minnesota is on the extreme northwest corner of its range. In Wisconsin it is listed as of 'Special Concern'. It can grow here but winter hardiness is of concern and it needs limestone and calcareous soils such as found in SE Minnesota.
There are six species of Oak generally found in parts of Minnesota that are not considered hybrids or rarities that have not been collected in the last 100 years. These are: White Oak, Q. alba; Swamp White Oak, Q. bicolor; Northern Pin Oak, Q. ellipsoidalis; Bur Oak, Q. macrocarpa; Northern Red Oak, Q. rubra. and Black Oak, Q. velutina. Chinkapin Oak (Chestnut Oak, or Yellow Oak), Q. muhlenbergii was native but is historical only now, last collected in 1899; Scarlet Oak, Quercus coccinea, can also grow here as can Pin Oak, Quercus palustris, but neither are native.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"