Minute to rather robust, usually acaulescent, clustered, spiny, pleonanthic, dioecious palms. Stem subterranean, decumbent or very short and erect, usually obscured by the leaf bases, the internodes short, often with abundant adventitious roots, rarely with short stilt roots, sucker buds leaf opposed at angles of 90–180° from the subtending leaf, very rarely developing as whip-like shoots rooting at their tips. Leaves very small to robust, pinnate, or entire, bifid, with pinnate venation, marcescent; sheath splitting opposite the petiole, unarmed at the extreme base, otherwise very sparsely to very densely armed with robust, scattered or whorled spines and usually with abundant caducous or persistent scales, sheath mouth frequently bearing a tattered ligule-like structure; petiole channelled adaxially near the base, rounded distally and abaxially, variously armed with spines and indumentum, often fiercely so; rachis armed as the petiole, but more sparsely; leaflets single-fold, where pinnate, except for the terminal pair, linear or sigmoid, acuminate or very rarely deeply lobed at the tip, regularly arranged or grouped and fanned within the groups, variously armed with short bristles along the main veins and margins, terminal pair compound, joined along the midline, deeply lobed at the tip, where leaf entire, bifid, the apical margins deeply lobed or almost entire, abaxial blade surface often with a dense covering of powdery indumentum, midribs prominent adaxially, transverse veinlets usually conspicuous. Inflorescences axillary but enclosed within the sheath of the subtending leaf, and emerging through a slit along the midline of the abaxial surface of the sheath, inflorescences usually short, sometimes spicate, more often with 1 or 2 orders of crowded or spreading branches, occasionally hidden by detritus, sometimes arching out of the crown, very rarely whip-like with the tip metamorphosing into a vegetative axis, rooting and becoming established as an independent plant, staminate inflorescences usually branched to at least 1 more order than the pistillate; peduncle usually short; prophyll usually rather inconspicuous, partly enclosed within the leaf sheath slit, tubular, 2-keeled, irregularly tattering; peduncular bracts several, tubular at the base with irregularly tattering, frequently densely scaly limbs; rachis usually longer than the peduncle; rachis bracts like the peduncular bracts; rachillae cylindrical, catkin-like, exposed or hidden by the bracts, bearing a tight spiral of imbricate, triangular or low, rounded bracts, sometimes connate laterally to form a continuous spiral, sometimes very small and scarcely imbricate, each, except for the proximal and most distal few, subtending flowers and sometimes also a dense pile of hairs. Staminate flowers borne in dyads with 2 small prophyllar bracteoles, these sometimes split and variously connate to each other, the flowers exserted from the pit at anthesis; calyx tubular, variously split to give 3 lobes, sometimes distinct almost to the base, chaffy, striate; corolla with a short stalk-like base, and a long proximal tube, bearing 3 triangular, ± hooded, valvate lobes; stamens 6, borne at the mouth of the corolla tube, filaments short, wide basally, anthers rounded to elongate, introrse; pistillode minute or absent. Pollen spheroidal or oblate-spheroidal; aperture a presumed meridional zonasulcus, occasionally incompletely so, rarely equatorial disulcate; ectexine tectate and spinose, rarely spinulose, or psilate and sparsely perforate or, semitectate and spinulose, or gemmate, aperture margins similar to surrounding ectexine; infratectum columellate; longest axis 22–34 µm; post-meiotic tetrads tetragonal [16/20]. Pistillate flowers either solitary (Section Leiosalacca) or borne in a dyad with a sterile staminate flower (Section Salacca) similar to the fertile but with empty anthers; calyx of pistillate flower tubular at the base, distally with 3, triangular, striate lobes; corolla similar with 3, triangular, valvate lobes; staminodes 6, borne at the mouth of the corolla tube, the filaments usually elongate, anthers ± sagittate, empty; gynoecium tricarpellate, triovulate, covered in flattened, smooth, or erect spine-tipped scales, stigmas 3, fleshy, reflexed at anthesis, locules incomplete, ovules basifixed, anatropous. Fruit (1–)(2–)3-seeded, globose to pear-shaped or ellipsoidal, with apical stigmatic remains; epicarp covered in somewhat irregular vertical rows of reflexed scales, the scale tips smooth (section Leiosalacca) or spine-like and upward pointing (Section Salacca), mesocarp very thin at maturity, endocarp not differentiated. Seeds basally attached, conforming to 1/3 or 1/2 of a sphere (depending on number reaching maturity), sarcotesta very thick, sour or sweet, inner seed coat very thin, endosperm homogeneous, the apex with a pit; embryo basal. Germination adjacent-ligular; eophyll entire bifid. Cytology: 2n = 28.
Acaulescent, clustering palms, often forming dense thickets, in Southeast Asia and West Malesia; sheaths and petiole are densely armed with long spines; flowering is pleonanthic and the inflorescence emerges from a slit in the back of the leaf that subtends it; the sarcotesta is easily separated from the rest of the seed.
Salacca species are plants of the undergrowth of primary tropical rain forest. However, they may be left after the surrounding forest has been destroyed to persist in the open, because of their usefulness as a source of fruit and building materials. Many species favour swampy valley bottoms where they form rather dense spiny thickets. Other species may be found on hillslopes or ridgetops. S. rupicola grows in the crevices of limestone cliffs and in the dwarf forest on limestone hilltops.
About 20 recognised species, but several more remain to be described; distributed from Burma and Indochina, south and eastwards to Borneo, Java, and the Philippines. Salacca zalacca, wild in Java and Sumatra, has been introduced into the Malay Peninsula, Borneo, Celebes, the Moluccas, and Bali for its excellent fruit. The greatest number of species and morphological diversity is found in the Malay Peninsula and Borneo.
Salacca zalacca is cultivated for its excellent fruit, and fruits of other species are eaten although they are sometimes very sour. Petioles of S. wallichiana are sometimes used in house construction in Thailand (Dransfield 1981c). The leaves of several species provide temporary thatch. The spiny petioles of S. zalacca are occasionally employed in Java to prevent thieves from climbing fruit trees and bats from roosting on roof beams.