Depending on the growing conditions, live oaks vary from the shrubby to large and spreading: typical open-grown trees reach 15 meters (50 feet) in height, but may span nearly 50 meters. Their lower limbs often sweep down towards the ground before curving up again. They can grow at severe angles, and Native Americans used to bend saplings over so that they would grow at extreme angles, to serve as trail markers. They drop their leaves, and grow new ones, within a few weeks in spring. The bark is furrowed longitudinally, and the acorns are small, but long and tapered. The branches frequently support other plant species such as rounded clumps of ball moss, thick drapings of Spanish moss, Resurrection fern, and parasitic mistletoe.

This rounded, deciduous tree eventually has widespreading branches which are green when young and covered with spines, often becoming grey and sometimes losing their coarse, sharp spines, Young trees can have a columnar or upright form. The spiny trunk is unusually thick and remains green even on older trees. Floss-Silk tree grows rapidly the first few years, then more slowly. Some trees maintain a relatively narrow crown with one straight trunk while others are wide-spreading, particularly on older specimens. The large, showy, pink and white, five-petaled flowers, which somewhat resemble narrow-petaled hibiscus, are produced in small clusters in fall and winter (usually October) when the tree is nearly bare. The fruits are large, eight-inch-long, pear-shaped, woody capsules, filled with silky, white, kapok-like floss and pea-like seeds. Floss from the seeds was used for stuffing pillows and thin strips of the bark have been used to make rope.