Cucumber magnolia is a medium-sized tree with rather slender branches and a dense, pyramidal crown.
Leaves are alternate, simple, scattered along the stem, 5–10 inches long, 2½–6 inches wide; margin lacking teeth, wavy; upper surface yellow-green, lower surface paler, somewhat hairy.
Bark is dark brown to gray, with thin, long grooves separated by narrow, scaly ridges.
Twigs are stout, red to brown, hairy and shiny at first, brown to gray and smooth later; pores small, numerous; bud at tip about ½ inch long, densely hairy.
Flowers April–May, at the tip of the twig, solitary, slightly fragrant, cup-shaped, upright, smooth, with 6 petals; petals greenish yellow, 2–3 inches long, broadest near the tip; stamens numerous; flower stalk ¾–1½ inches long.
Fruits August–October; fruit a cucumber-shaped cone composed of a tightly packed cluster of dried fruits, red to brown, 2–3 inches long, often curved, smooth; seeds red, each hanging by a thread after fruit splits open, globe-shaped, flattened.
Similar species: Several species of magnolias are cultivated in Missouri. Our only other "native" magnolia is umbrella magnolia (M. tripetala), which has been recorded from only a single location in St. Louis County and may actually be an introduced occurrence. Tulip tree, or yellow poplar (Liriodendron tulipifera), common in landscaping, is in the same family as the magnolias.