The stems, which die down in the autumn, are erect at 3 to 4 feet (1.2 m) high, simple, or putting out only a few lateral branches. The leaves, which are shortly petioled, are roundish, ovate-cordate, 2 to 3 inches (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 stellated hairs. The flowers are shaped like those of the common Mallow, but are smaller and of a pale colour, and are either auxillary, or in panicles, more often the latter.
The stamens are united into a tube, the anthers, which are kidney-shaped and one-celled. The flowers are in bloom during August and September, and are followed by, as in other species of this order, by the flat, round fruit which are popularly called ‘cheeses’.
There have been extremely rare reports of allergic reactions. Although there are no known reports or studies about marshmallow allergy, allergic reactions to marshmallow may occur.