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Avicennia marina ssp. eucalyptifolia (Valeton) J.Everett 1994
pronounced: av-ih-SEN-ee-uh mar-EE-nuh subspecies yew-kuh-lip-tee-FOH-lee-uh
(Acanthaceae — the black-eyed Susan family)
common name: Grey Mangrove
Avicennia was named for Avicenna – Ibn Sina (980-1037), a Persian physician-philosopher; marina refers, as you would expect, to the seaside, and eucalyptifolia says that it has leaves like the eucalypts. This is another of the three subspecies of Avicennia marina currently recognized, together with ssp. australasica and ssp. marina. The taxonomy of this genus is very contentious, mainly due to its immense variability. Generally speaking, ssp. marina is found in south-western Australia, Asia, and the margins of the Indian Ocean; ssp. eucalyptifolia in northern Australia, southern New Guinea and the southern Solomon Islands; and ssp. australasica in eastern and south-eastern Australia, mainly south of about Rockhampton, although there is a considerable overlap, and the distinction between the respective subspecies breaks down through free interbreeding. There appear to be distinct differences between the two populations found on Magnetic Island, with ssp. australasica along the northern end of Geoffrey Bay in particular, and ssp. eucalyptifolia in Florence Bay and a few other isolated populations as in the creek behind the Bowls Club in Geoffrey Bay.
This subspecies can grow into a large tree, up to 30 m high, but is usually much smaller. The bole is straight up to 10 or more m in height, with no buttresses, spines, aerial roots or stilt roots. The bark is brown (looking almost white when dry) or greyish green, often slightly rough, often scaly, or flaky with thin flakes.
The leaves are spaced out along the branches: simple, opposite, with a petiole about 1 cm long. The lamina is more-or-less lanceolate, broadest below the middle, the apex long-tapering or slightly acuminate – there are no oil dots, domatia or stipules.
The inflorescences are terminal, the unstemmed flowers bisexual, small (less than 6 mm in diameter), with distinct sepals and petals, orange in colour. The flowers are fragrant, rich in nectar, and are pollinated by insects.
The fruits (dehiscent capsules) are arranged on a branched axis, and are 10 – 20 mm long, with the diameter slightly smaller than the length, and grey, greenish grey or pale brown in colour. There are 1 or 2 seeds, not winged.
Members of the genus are among the most salt-tolerant of mangroves, and are often the first to colonize new deposits of sediment. The sap is salty and excess salt is secreted through the leaves. The spreading root system provides stability in fairly unstable substrates. The embryos exhibit cryptovivipary, where they start to develop before the seed is shed, but do not break through the outside of the fruit capsule.
Photographs taken in Florence Bay, 2005, & Arcadia, 2016
Page last updated 9th October 2016