Quercus marilandica acorns

Quercus marilandica (Blackjack oak) is a small oak, one of the red oak group Quercus sect. Lobatae, but fairly isolated from the others. It is native to the southern and central United States, with populations following the eastern seaboard north to Long Island.

It is a small deciduous tree growing to 15 m tall, with bark cracked into rectangular black plates with narrow orange fissures. The leaves are 7-20 cm long and broad, and typically flare from a tapered base to a broad three-lobed bell shape with only shallow indentations. They are dark green and glossy above, pubescent underneath, and often remain attached to the twigs through the winter after turning colors from red to brown in the fall. The acorn is small, 12-20 mm long and 10-18 mm broad; like other red oaks, it takes 18 months to mature.

The Blackjack oak grows in poor, thin, dry, rocky or sandy soils where few other woody plants can thrive, usually on low ground, from sea level up to 900 m altitude. It does not have the beautiful form of many oaks, but is nonetheless a valuable tree for growing in problem sites. It is sometimes an understory tree in pine stands on sandy knolls in the southeastern US. Along the coastal plain of New Jersey the probability of finding this species is increased in relatively sunny, open areas such as those near coastal salt marshes. It often occurs near Scarlet and Post Oaks as well as Pitch Pine; understory companions include winged sumac, bracken, sweetfern, and bayberry.

An oak is a tree or shrub in the genus Quercus ( /ˈkwɜrkəs/; Latin "oak tree"), of which about 600 species exist. "Oak" may also appear in the names of species in related genera, notably Lithocarpus. The genus is native to the northern hemisphere, and includes deciduous and evergreen species extending from cold latitudes to tropical Asia and the Americas.

Oaks have spirally arranged leaves, with a lobed margin in many species; some have serrated leaves or entire leaves with a smooth margin. Many deciduous species are marcescent, not dropping dead leaves until spring. The flowers are catkins, produced in spring. The fruit is a nut called an acorn, borne in a cup-like structure known as a cupule; each acorn contains one seed (rarely two or three) and takes 6–18 months to mature, depending on species. The live oaks are distinguished for being evergreen, but are not actually a distinct group and instead are dispersed across the genus.