Milky mangroves grow as shrubs or trees (up to 15 metres).
Excoecaria agallocha (milky mangrove) is a member of the family Euphorbiaceae and is distributed from northern New South Wales, through Queensland and Northern Territory to Western Australia. In Queensland, it is a mangrove of the upper tidal limits and occurs at the landward fringe of the community often in association with the grey mangrove (Avicennia marina), the white-flowered black mangrove (Lumnitzera racemosa), and the river mangrove (Aegiceras corniculatum). It is often found on small sandy ridges in mixed stands of mangroves.
Milky mangroves may grow as shrubs or trees up to 15 metres in height with grey to fawn brown bark marked with longitudinal rows of corky brown air pores (lenticels).
Surface roots occur in this species which when exposed to air at low tide permit the uptake of oxygen. Leaves are pale green to yellowish and measure from 5 to 11 cm in length and 2 to 4 cm in width. The leaves are basically oval in shape, with a pointed tip, rounded at the base and often finely toothed at the edges and are attached alternately on the stems.The major feature of this mangrove is the milky sap which exudes from the plant when branches or leaves are broken. The sap is poisonous and can cause severe skin irritation and temporary blindness if contact is made with the eyes.
Flowering and fruiting
Minute flowers 2mm in diameter appear from October to April. Male and female flowers are located on separate trees and occur on spikes 2.5 to 3.5cm long at the base of the previous years leaves or at old nodes.
Fruiting occurs throughout the year with the appearance of small three-lobed fleshy green capsules (approximately 5mm in diameter) arranged in clusters. Each lobe contains a single seed which is released from the capsule as it opens. The seeds are buoyant due to an air space within the seed coat and float with the tides and currents until a suitable soil is encountered. Germination then takes place and the seedling development occurs.
Any salt taken up accumulates in the leaves and may be removed as leaves grow old and fall from the plant.
The timber of the milky mangrove is light, soft and pale in colour. Overseas it is used for incense and in canoe construction while the sap is used for fish poison and medicinally in treating chronic ulcerous diseases such as leprosy. Important non-destructive uses include a source of pollen for beekeepers, shoreline protection and provision of habitat for marine and terrestrial wildlife.