perennial very large grasses with thick, woody, branched rhizomes.
The aboveground stems are annual, straight, thick, hollow and sometimes slightly grooved.
The basal leaves are very large, long-stemmed, whole, palmately lobed or toothed, sometimes wavy along the edge; petioles are cylindrical or polyhedral, equipped with large bell-shaped at the base. The stem leaves are smaller.
The stem ends with a large paniculate inflorescence.
The flowers are mostly white or greenish, rarely pink or blood-red; they are bisexual or, due to underdevelopment, same—sex. The perianth is simple, six-leaved, the leaves of which are either all the same with each other, or the outer ones are somewhat smaller than the inner ones, after pollination the perianth withers. Stamens 9, in two circles, and the outer circle is doubled; only Rheum nobile Hr. has six stamens, since the outer circle is not doubled. There is one pistil, with an upper single-nest triangular ovary; there are three columns, with head-kidney-shaped or horseshoe-shaped stigmas.
The fruit is a triangular wide- or narrow-winged nut. The seed is albuminous, the embryo is central.