Avicennia marina aka Grey Mangrove

Avicennia marina, or white mangrove, belongs to the Acanthaceae family. It grows along tropical and subtropical shores of the Old World. Its range spans Africa, Arabia, Asia, Australia and New Zealand. It lives on tidal mudflats, sandy shores and brackish river banks. It can dominate mangrove swamps and colonise new mud banks. The cited 2011 IUCN assessment lists it as Least Concern. Coastal building and resource harvest still threaten its habitat.

This evergreen grows as a shrub or small tree. Its loose, rounded crown has an open branch structure. Most plants reach about 3–33 feet [1–10 metres] tall. Some reach 82 feet [25 metres], chiefly in northern Australia. The trunk may grow straight or bend as it develops. Its width reaches about 0.7–1.3 feet [0.2–0.4 metres]. Upright breathing roots rise from the mud around the plant. Leaf pores release excess salt, which can leave visible crystals. Insects pollinate the flowers, and the plant is self-fertile.

White mangrove needs full sun and suits warm coastal sites. It grows best at daytime temperatures of 20–34°C. Temperatures of −1°C or below can kill it. Its salt tolerance spans fresh standing water to highly saline conditions. It can also cope with seasonal drying and low rainfall. These traits suit tidal sites rather than most garden beds. The plant grows fast and can regenerate in large numbers. Its ability to settle new mud banks gives it coastal value.

Fresh seed offers one means of raising new plants. Sow it soon after ripening, since drying can damage it. Fungi can also harm seeds kept moist in storage. Young seedlings grow best with access to fresh water. Older seedlings grow better with some seawater mixed in. Air layering and root suckers have also worked. The evidence gives no wider list of pests or diseases.

People use the wood for poles, boats, furniture and handles. They also burn it as fuel or make charcoal. The bark supplies tannins and red to brown dyes. Smoke from the wood serves as a mosquito repellent. Traditional medicine uses the leaves, bark, resin and wood ash. These uses do not establish safe or proven treatments. People sometimes eat the cooked cotyledons, or seed leaves. These parts may contain toxic compounds, so they are not a casual food.