The species of siltbush are shrubs or subshrubs reaching 15 to 150 cm. The stems grow erect or ascending and are much branched and woody. The old bark is gray brown. The green to grayish leaf blades can be elliptic, ovate, obovate, spatulate, or linear-oblanceolate, with entire margins and prominent midveins. The inflorescences consist of glomeruled male flowers arranged in interrupted axillary or terminal spikes or panicles, and of female flowers in terminal and axillary interrupted panicles. In fruit, the bracteoles enclosing the fruit become accrescent, folded along the midribs and connate nearly to the apex. Their shape can be orbicular, broadly elliptic, or cordate, their margins are usually entire, but sometimes wavy or extended into two wings, their surface is flat or ribbed, glabrous or hairy. The vertically or horizontally orientated seed has a brown to yellowish-brown, thin membranous seed coat. The four shrubby species occur in arid and semiarid regions of western North America.