Arenga Labill.

Understory shrubs to large trees. Stems clustered, sometimes spreading by stolons, less often solitary, usually covered with persistent, fibrous leaf bases. Leaves 5-30, pinnate, seldom undivided; leaf sheaths open, fibrous, commonly persisting on stems; petioles usually covered with distinctive scales; pinnae linear to rhomboid, sometimes lobed on margins, always jagged at apices, bases sometimes with an ear-shaped projection overlapping rachis; pinnae regularly or irregularly arranged, basal few borne in clusters, silvery gray abaxially. Plants usually semelparous; flowering proceeding from top of stem downward (basipetal), rarely in opposite direction (acropetal). Inflorescences branched to 2 orders, rarely spicate, borne among leaves, usually unisexual by suppression of either female or male flowers, solitary or rarely several at a node, covered with several persistent bracts, female inflorescences commonly produced first at apex of stem, and male ones later, below; rachillae 1-100 or more; flowers borne in triads with a central female flower and 2 lateral male flowers. Fruits red, yellowish, or purplish, large, ellipsoid, globose, ovoid, or oblong, 1-3-seeded; mesocarp with irritant crystals of calcium oxalate; endosperm homogeneous; germination remote; eophylls undivided or bifid with jagged margins.

Mainly primary rainforest species, some tree-like and sometimes gregarious, others occurring as forest undergrowth palmlets (Du Puy & Telford 1993).

Arenga pinnata (Wurmb) Merr. (Sugar Palm, Areng Palm, Black Sugar Palm, Gomuti Palm) of tropical Asia is an important economic plant widely cultivated in the tropics as a source of sugar (sugar in the sap is tapped from the peduncles of young inflorescences), sago, wine (sugary sap is drunk or fermented to make palm wine), fibre (the trunk yields starch, fibres and rope) and thatch (leaves). It is a monocarpic species which builds up a large reserve of carbohydrate in its trunk prior to flowering. Several species are grown as ornamentals, e.g. A. caudata (Lour.) H.E.Moore (Tailed Arenga) from Thailand, A. engleri Becc. (Formosa Palm) from Taiwan and Japan.