Geranium arboreum, a member of the Geraniaceae (geranium) family, is a large, branched, spreading shrub 2 to 4 m (6.6 to 13 ft) tall. The green and somewhat hairy leaves, alternating closely on the stem, are oval- or heart-shaped, usually 4 to 7 cm (1.6 to 2.8 in) long and 2.5 to 4.5 cm (1 to 1.8 in) wide with 5 to 8 noticeable veins and 8 to 14 small teeth on each edge. The leaf stalks (petioles) are 1 to 3 cm (0.4 to 1.2 in) long and are encircled beneath (subtended) by tiny (12 to 14 mm; 0.5 to 0.6 in), hairy, leaf-like appendages (stipules), which persist after the leaves have fallen. Magenta flowers, 20 to 25 mm (0.8 to 1 in) long, occur in short-stalked groups of usually one to four, originating from the point of attachment of leaves to the stem. The upper three petals are erect, and the lower two petals are bent abruptly backward. Its flowers are the only ones in the genus that are zygomorphic (not symmetrical like pie slices around a central point). A single dark purple, net-surfaced 2.5 mm (0.1 in) seed is produced in each of five cells of the elongated fruit.