Pecan is a large tree with a narrow, pyramid-shaped crown in the forest, and a broad and rounded crown in the open; it is the largest of all the hickory trees.
Leaves are alternate, compound, 9–20 inches long, with 9–17 leaflets; leaflets 4–8 inches long, 1–3 inches wide, lance-shaped, curved; margins toothed; upper surface dark green; lower surface paler, smooth to hairy.
Bark is grayish brown to light brown when young, becoming dark reddish brown with age; ridges long, flat, loose.
Twigs stout, reddish brown, hairy, with numerous elongated orange-brown pores; bud on end of twig yellow-brown.
Flowers April–May, male catkins and female clusters separate on the same tree.
Fruits September–October, in clusters of 3–10; husk thin, aromatic, reddish brown, winged, splitting along 4 ridges at maturity to expose the nut. Nut thin, 1–3 inches long, 2–4 times longer than broad, cylindrical, pointed at the tip, light brown to reddish brown, with irregular black markings on the shell; kernel sweet and edible.