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Black mangrove

Black mangroves grow in brackish water and tolerate a wide range of salinity. The species reaches heights of 20-25 m and a diameter at breast height of 40 cm. Black mangrove’s opposite, narrow elliptical leaves are silver green, thick, leathery and close to 10 cm long. Glands on their greyish and hairy undersides of are often encrusted with salt secreted from glands on their greyish and hairy undersides. The species’ small white flowers grow in clusters at the leaf axils and on twig tips.

The black mangrove has small, white flowers and bares fruit throughout the year. Like the red mangrove, it is viviparous. The species has dark green, flattened bean shaped propagules that are 2 to 3 cm long. The obligate dispersal period for the black mangrove’s propagules is estimated at 14 days, thus much shorter than the red mangrove’s. But similarly, the fallen propagules of the black mangrove can float in salt water for a very long time without rooting in the absence of suitable substrate areas. These areas of sand, silt, mud or clay must provide shelter from waves.

Avicennia germinans has a dark and scaly bark and a multitude of thin, upright roots called pneumatophores that stem from shallow underground horizontal cable roots by the hundreds on the ground around the tree. The purpose of these pneumatophores, or breather roots, is to oxygenate the tree’s underground rooting system. Pneumatophores also trap sediments and control erosion.

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