I’ve long been fascinated by bird’s-nest ferns (Asplenium nidus and similar species, such as A. antiquum and A. australasicum). They get their name because their very unfernlike fronds—they’re simple and tongue-shaped rather than highly divided like most fern fronds—that form an open, cuplike rosette, much like a bird’s nest. Also, to carry the bird analogy a step further, their young fronds, still pale green, are rolled up like a ball and can be said to look like eggs sitting in the hairy brown center of the nest, something you’d most likely see only in spring, just as the plant is starting to go into a growth spurt.
Curiously, sometimes birds actually do build nests in bird’s-nest ferns. The Madagascar serpent-eagle (Eutriochis astur), for example, often forgoes building a nest of its own and simply sets up shop in the ready-made nest of a large bird’s-nest fern.
A Way of Coping With Harsh an Aerial Lifestyle
As cute as this bird’s nest habit might seem to humans, it didn’t evolve that way to please our eye, but has a very practical purpose.
Bird’s-nest ferns are essentially epiphytes (plants that grow on tree branches), although they’re also found on rock faces and sometimes fall to the ground to continue growing as terrestrial plants. The epiphyte lifestyle is a difficult one: the bare bark their roots cling to offers little in the way of moisture and minerals, but bird’s-nest ferns’ special shape helps them compensate. They catch and hold fallen leaves, bird droppings and other detritus which can then decompose slowly, feeding the fern. The detritus also holds rainwater well, helping the fern cope with dry spells.
Botanists call the plants with this growth habit “trash-basket plants”, a rather unfortunate name, don’t you think? Other names include litter-gathering plants, nest-epiphytes, and detritophylic plants. I prefer to think of them all as bird’s-nest plants, a much more sympathetic description.
Other Bird’s-Nest Ferns
But Asplenium nidus and its cousins are not the only bird’s-nest plants. Many epiphytic plants have evolved similar habits, that is, using their foliage to catch and feed on fallen leaves and as a means of storing moisture.
Basket ferns (Drynaria spp.), for example, which cling to tree trunks or rocks, have even evolved two types of fronds. They produce both long, green, fertile fronds, deeply cut, that both collect the sun’s energy like most leaves and also produce spores for future generations of ferns, and “shield fronds.” These are short, entire and sterile (never produce spores) and rapidly turn brown. They form a “basket” that collects litter and organic debris, thus supplying the fern with nutrients. Thus shield fronds are useful even after they are dead!
There are many other ferns with similar habits, including one commonly grown as a houseplant: the staghorn fern (Platycerium spp.). Staghorn ferns too have green, fertile fronds that reach outwards to catch the sun and short, shield or cup-shaped ones that quickly turn brown. Pressed against a trunk or rock surface, they protect the fern’s roots from damage and desiccation, but the top margin opens outward to catch forest litter and water. Most owners of staghorn ferns have no idea of the real purpose of these curious shield fronds.
Why should ferns have the exclusivity of a good idea? Epiphytic plants the world over have developed a similar strategy.
The vast genus Anthurium contains over 1000 species of terrestrial, climbing and epiphytic plants, some of which (including A. andreanum and A. scherzerianum and their hybrids) are commonly grown as flowering houseplants, but they’re not trash-basket—excuse me!—bird’s-nest types. However, some 100 species, including A. hookeri, A. plowmanii, A. cubense and A. salvinii, have developed the bird’s-nest habit, and they are often quite spectacular due to their large size.
The giant, thick, paddle-shaped leaves can be 3 feet long and form a rosette inevitably filled with leaf litter in the wild, where they usually grow as epiphytes at first before their enormous weight sends them crashing to the ground to continue their existence as terrestrial plants. Their thick, orchid-like roots actually grow upward, not down, into the litter, all the better to feed themselves. They make stunning and easy-to-grow houseplants … if you have the space for them.
And there are trash-basket orchids, as well. Bulbophyllum beccarii is one. Its very unusual paddle-shaped leaves trap fallen leaves and flowers, although they work as individual traps: it doesn’t really take on a nestlike shape.
Most other bird’s nest orchids, notably in the genera Ansellia, Cyrtopodium and Grammatophyllum, have a very different growth habit. They develop baskets of upright-growing aerial roots designed to catch leaves and other debris. They tend to be huge orchids in nature (again, birds, including such enormous ones as eagle owls [Bubo bubo], have been known to nest in their root basket). Curiously, in pots, they generally only produce root baskets when stressed by a lack of nitrogen.
The Ultimate Trash-Basket Plants
This search for bird’s-nest plants inevitably leads to the most efficient water and leaf catchers of all: tank bromeliads. These plants, in all sorts of genera of the Bromeliad family, including Aechmea, Billbergia, Guzmania, Neoregelia, Vriesea and even some Tillandsia species, are epiphytic or lithophytic (grow on rocks) and form a rosette of leaves so tightly bound than it holds water perfectly. As a result, the growing point of these tree-growing plants is actually under water! Curiously, they mostly absorb water and minerals through trichomes (scales) on their leaves rather than through their roots.
Not only do these tanks catch rainwater, fallen flowers and leaves, bird and animal droppings, etc., they also serve as a home for all sorts of small animals, from microbes to tadpoles and mosquito larvae … whose excrements also help feed the plant. Each tank bromeliad is essentially an environment unto itself.
Tank bromeliads make great houseplants and you’ll find various kinds in garden centers everywhere.
Whether you call them trash-basket plants, leaf-litter plants or bird’s-nest plants, these plants are absolutely fascinating and well worth not only studying, but growing. Try one today!