General: spreading annual, rarely biennial, mostly 20-60 cm tall, with short, somewhat stiff hairs.
Leaves: alternate, the stalks several times the length of the blades, the blades cordate to reniform, about 1.5-4 cm long, blunt- to sharp-toothed, very inconspicuously 5 to sometimes 7-lobed. The 2 stipules at bases lanceolate, 0.5-1 cm long.
Flowers: pale pink to nearly white, in clusters of 1 to 3 from leaf axils, on stalks about 1 cm long. Calyx about 6-8 mm long, the 5 lobes triangular, pointed, about half as long. The 3 bracteoles at the base narrowly lance-shaped. The 5 petals obovate, about 10 mm long, notched at the tips. Stamens numerous, joined to a tube at the base, freed higher up singly or in pairs. Style branches 10-15, with stigmas most of their length, not terminally enlarged.
Fruits: capsules, round, flattened lengthwise, cheese-shaped, composed of several wedge-shaped segments, these rounded on the back, short-hairy but otherwise nearly or quite smooth.
Fields, gardens and disturbed areas, in w. and s.c. parts of MT. Introduced from Europe, a fairly common weed throughout the U.S.
Leaves and young shoots of common mallow are edible raw or cooked. Having a mild pleasant flavor, they are said to be highly nutritious. They can be added in quantity to salads, and make an excellent lettuce substitute, they can also be cooked as greens. The leaves are mucilaginous, when cooked in soups etc they tend to thicken it in much the same way as okra (Abelmoschatus esculenta). Some people find this mucilaginous texture unpleasant, especially if the leaves are cooked. Immature seeds are edible raw or cooked. A pleasant nutty flavor, they are nice as a nibble but too small in most cases to collect in quantity. A decoction of the roots is used as an egg-white substitute for making meringue. The roots are brought to the boil in water and then simmered until the water becomes quite thick. This liquid can then be whisked in much the same way as egg whites. A tea can be made from the dried leaves.
Caution: When grown on nitrogen rich soils (and particularly when these are inorganic), the plant tends to concentrate high levels of nitrates in its leaves. The leaves are perfectly wholesome at all other times.
All parts of the plant are astringent, laxative, urine-inducing, and have agents that counteract inflammation, that soften and soothe the skin when applied locally, and that induce the removal (coughing up) of mucous secretions from the lungs. The leaves and flowers can be eaten as part of the diet, or a tea can be made from the leaves, flowers or roots. The leaves and flowers are the main part used, their demulcent properties making them valuable as a poultice for bruises, inflammations, insect bites etc, or taken internally in the treatment of respiratory system diseases or inflammation of the digestive or urinary systems. They have similar properties, but are considered to be inferior to the marsh mallow (Althaea officinalis), though they are stronger acting than the common mallow (M. sylvestris). They are seldom used internally. The plant is an excellent laxative for young children.
Cream, yellow and green dyes can be obtained from the plant and the seed heads. The root has been used as a toothbrush.