Focus on Flora: Mangrove Fern

Focus on Flora: Mangrove Fern

Cayman is home to the largest contiguous mangrove wetland in the Caribbean — an astounding 8,655 acres — so it's no surprise it also serves as home to the mangrove fern, or Acrostichum aureum.

A pantropical native, mangrove fern can be found across Asia, Africa and the Americas growing in riparian areas, and in or near mangroves. It has a high tolerance for salinity in the water but grows in freshwater habitats as well.

This rapid growing fern can grow alone or in clusters due to its fibrous underground plant stems, which extend horizontally and are continuously growing. The root system also aids the fern in stability as its ability to tolerate salinity means it is also subject to varied movements from tidal waters and flooding. Although fit to grow and coexist rather happily with mangroves, the large clusters can become problematic in areas of active mangrove restoration, where they pose a threat of competition for nutrients and overcrowding.

Topping out at around 15 feet with a spread roughly two-thirds that height, the mangrove fern needs plenty of room to thrive. Tolerating a wide range of sunlight, it does need high light to flourish, as well as rich, humusy soil and plenty of water. The exquisite leathery, deep-green fronds can reach up to 6 feet in length, with the reddish-brown sporangia adding a touch of colour to the end of the frond. The sporangia are enclosures where spores are formed during the process of meiosis and are the reproductive organs of the fern. They are felted and rough to the touch and disperse naturally through the wind, or by way of animals brushing against them.

Rumoured to have medicinal properties — although not yet confirmed — they are useful in other ways. The fronds are used in some regions for thatching, and the young leaves are often eaten in salads or in curry dishes as a delicacy. Because ferns are known to have high concentrations of oxalates, careful care should be taken when cooking or preparing them for consumption.

In Camana Bay, the mangrove ferns reside in a partly shady bed near Gardenia Court.

This article was originally featured in the September/October 2023 print edition of Camana Bay Times.

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