The stems, which die down in the autumn, typically grow 3 to 4 ft (0.91 to 1.22 m), but can reach 6.5 feet (2.0 m) and put out only a few lateral branches. The leaves are shortly petioled, roundish, ovate-cordate, 2 to 3 in (51 to 76 mm) long, and about 1?1/4 inch broad, entire or three to five lobed, irregularly toothed at the margin, and thick. They are soft and velvety on both sides, due to a dense covering of stellate hairs. The flowers are shaped like those of the common mallow, but are smaller and of a pale colour, and are either axillary, or in panicles, more often the latter.
The stamens are united into a tube, the anthers, kidney-shaped and one-celled. The flowers are in bloom during August and September, and are followed, as in other species of this order, by the flat, round fruit which are popularly called "cheeses".
The common mallow is frequently called "marsh mallow" in colloquial terms, but the true marsh mallow is distinguished from all the other mallows growing in Great Britain by the numerous divisions of the outer calyx (six to nine cleft), by the hoary down which thickly clothes the stems and foliage, and by the numerous panicles of blush-coloured flowers, paler than the common mallow. The roots are perennial, thick, long and tapering, very tough and pliant, whitish yellow outside, white and fibrous within.
The generic name, Althaea, is derived from the Greek ???e?? (to cure), from its supposed healing properties. The name of the family, Malvaceae, is derived from the Latin malva, a generic name for the mallows and the source of the English common name mallow.