Tree Mallow

Appearance

It is a shrubby annual, biennial or perennial plant growing to 0.5–2 m tall. The leaves are orbicular, 8–18 cm diameter, palmately lobed with five to nine lobes, and a coarsely serrated margin. The flowers are 3–4 cm diameter, dark pink to purple and grow in fasciculate axillary clusters of two to seven.

Habitat

"Malva arborea" tolerates sea water to varying degrees, at up to 100% sea water in its natural habitat, excreting salt through glands on its leaves. This salt tolerance can be a competitive advantage over inland plant species in coastal areas. Its level of salinity tolerance is thought to be improved by soil with higher phosphate content, making guano enrichment particularly beneficial. It grows mainly on exposed coastal locations, often on small islands, only rarely any distance inland.

Uses

The leaves of the species are used in herbal medicine to treat sprains, by steeping them in hot water and applying the poultice to the affected area. It is theorised that lighthouse keepers may have spread the plant to some British islands for use as a poultice and to treat burns, an occupational hazard.
Thought to have been used as an alternative to toilet paper. The seeds are edible and are known in French as "petit pains", or "little breads".

Tree mallow was considered a nutritive animal food in Britain in the 19th century, and is still sometimes used as animal fodder in Europe. For human consumption, some sources describe the leaves of tree mallow as edible, although not as palatable as common mallow, unless cut very thinly, because of the very velours-like hairy mouth-feel.

"Malva arborea" has long been cultivated in British gardens, as described in the 1835 self-published book "British Phaenogamous Botany", which used the then-common name "Sea Tree-mallow": "This species is frequently met with in gardens, where, if it is allowed to scatter its seeds, it will spring up for many successive years, and often attain a large size. The young plants will, as Sir J. E. Smith observes, now and then survive one or more mild Winters; but having once blossomed it perishes."

While sometimes detrimental to seabird habitat, management of tree mallow has been successfully employed to shelter nesting sites of the threatened roseate tern, which requires more coverage than common terns to impede predation.