The leaves are opposite, palmately 5-lobed large, 10–25 cm long and broad with a 5–15 cm petiole, with leathery texture and thick veins protruding on the underside surface with toothed edges, and dark green in colour with whitish underside; some cultivars have purple-tinged or yellowish leaves. The leaf-stalk is frequently tinged red. The leaves are often marked with black spots or patches which are caused by the fungus Rhytisma acerinum. The monoecious yellow-green flowers are produced in spring on 10–20 cm pendulous racemes, with 20–50 flowers on each stalk. The 5–10 mm diameter seeds are paired in samaras, each seed with a 20–40 mm long wing which catches the wind and rotates when they fall; this helps them to spread further from the parent tree. The seeds are mature in autumn about 6 months after pollination. The sycamore is able to produce suckers from roots when they are exposed to sunlight after the mature tree has fallen.