Sweet gum trees have alternate, sharply (three- to seven-lobed) palmate leaves and bear upright spikes of greenish male flowers and round, drooping clusters of female flowers on the same tree. Spiny, dark-brown balls of seeds develop and often persist through the winter. The American sweet gum, or bilsted (A. styraciflua), which sometimes reaches 45 metres (150 feet) in moist lowlands but is usually half that height at maturity, is grown for its handsome foliage, shade, and scarlet autumnal colour. It is also valued for its heartwood, called red gum or satin walnut, which is used for quality furniture. The trees are tapped for liquidambar balm, though a more fragrant gum is collected from the Oriental sweet gum (A. orientalis). The Formosan gum (A. formosana), with three-lobed leaves, is widely grown as a garden tree in mild climates.