Malva trimestris aka Annual Mallow

Malva trimestris is an annual in the mallow family, Malvaceae. Its common names include royal mallow and annual tree mallow. Sources also list it under the name Lavatera trimestris. It comes from the Mediterranean, where it grows in sandy places near the sea. It is not native to Britain or Ireland. Despite its tree mallow name, it lives as an annual.

The plant grows upright and has a bushy, shrub-like form. Garden heights range from about 2–4 feet [0.6–1.2 metres]. RHS gives a lower range of 1.6–3.3 feet [0.5–1 metre]. Spread estimates range from 1.6–3 feet [0.5–0.9 metres] at the upper end. Tall plants may need stakes or other support. Straight stems bear bristles, while the green leaves lack hairs. Leaves grow alternately along the stems and have rounded, scalloped edges. Their bases are heart-shaped, and their blades have shallow lobes. Upper leaves tend to be smaller than lower ones.

Flowers open from July to September, spanning summer and early autumn. Each flower grows alone and forms a broad, shallow funnel. Blooms are white or pink, with dark red centres and veins. Flower width can reach about 0.33 feet [0.10 metres]. The flowers suit cutting as well as garden display. Brown to copper-coloured fruit appears in autumn. Removing spent blooms can help extend the flowering season.

Give this plant full sun and soil that drains well. Sandy or loamy soil suits it, across acid to alkaline conditions. It accepts dry to moist ground and needs moderate watering. In hot summers, some afternoon shade can help. It prefers cool summer nights and moderate rain. It also tolerates poor soil, salt, and coastal exposure. Sources list USDA zones 2–11 and the UK rating H4. It grows fast and needs little upkeep. Sow seed outdoors in spring, or start indoors for earlier flowers.

Use it in beds, borders, containers, and coastal or cottage gardens. It can also serve as an accent in cutting gardens. Plants may seed themselves in some places. Japanese beetles can damage leaves and flowers. Root rot, stem rot, leaf spots, and rust may occur. Young leaves are edible when cooked. PFAF reports no known hazards, but does not establish pet safety. Seeds contain oil, though the source leaves its uses unclear. PFAF lists no known medicinal use.