Tree ferns

Named for their tall, rigid trunk structures, tree ferns tower high in the cloud forest just below the summit of Mount Scenery, the highest point on Saba. If you spend time roaming underneath these massive plants, you’ll get a sense of what it may have been like to be a tiny dinosaur — researchers have found tree ferns in fossil records of the Jurassic and Triassic, meaning they’ve existed for more than 200 million years. Cyathea is the largest group of tree ferns, and on Saba, you’ll easily spot Cyathea arborea, the West Indian tree fern, which can grow to be almost 9 m/30 feet tall. This particular species is native to the Caribbean and nearby areas, but other tree fern species can be found in warm, moist areas all over the world (and occasionally in cooler climates, as well). 

Cyathea usually have hard, coarse trunks, which are essentially an accumulation of fern stems and modified roots that hold up the crown of leaves at the top. These fronds are some of the largest leaf structures found in the plant kingdom — on some species, they can grow to be up to 4 m/13 feet in length! When a frond first emerges from a young tree fern, it’s rolled up tight. As the plant matures, the frond lengthens, unfurls, and fans out into the air. Depending on the species of tree fern, the fronds may be covered in small, scale-like structures, hairs, or both, and some species even have spines at the base of their fronds. 

Like other ferns, tree ferns develop dusty brown pockets under each frond as they grow — these are groups of spores, which they use to propagate and multiply. These groups, called sori, usually have a protective membrane over them and can take many shapes, from a sphere to a multi-lobed blob. When powerful winds or a large enough animal rustles the fronds of a tree fern, the spores scatter and float through the forest until they land on a patch of soil in which they can take root. 

Several species of tree ferns have become rare because of commercial harvesting. The outer layer of their strong trunks create a fibrous substance ideal for raising orchids and other epiphytic plants; slices of their trunks produce a high-contrast, patterned material used in crafts; and entire sections of their trunks have been carved into keepsakes to be sold at tropical resorts. In rainforests — areas that are already under threat — these giants provide cover and habitat for their fellow plants and animals, making them another species in need of more protection as mighty residents of critical ecosystems.

Header image by Kai Wulf.