Mallow tree (Lavatera arborea), sometimes known as Malva arborea, is a species of mallow native to the coasts of western Europe and the Mediterranean region. It is a shrubby annual, or perennial plant growing to 1–2 m (rarely 3 m) tall. The leaves are orbicular, 8–18 cm diameter. The flowers are 3–4 cm diameter, dark pink to purple and grow in clusters of two to seven.
It grows mainly on exposed coastal locations, often on small islands, only rarely any distance inland. Lavatera 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.
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. Tree Mallow seeds may be transported between separated coastal areas by the floating fruit, and seabirds are considered a likely means of spread. The seeds are encased in an impermeable outer case, and can remain viable for years, even after extended immersion in saltwater.