When someone mentions the bird's nest ferns, what do we think of? Probably Asplenium nidus, A. australasicum, A. antiguum and, since last summer's sale, A. goudeyi. Actually, there are many more species than that and this article provides information about several of them.

First, I need to define what I mean by a bird's-nest fern. I am going to take a very narrow view and define them all as being Aspleniums with an erect rhizome, unbranched, and forming a single growing tip. Their fronds (lamina) are simple and form a regular rosette, usually upright, which makes a nest at the bottom capable of holding litter in the form of leaves, bird droppings, etc. The sori form long rows extending out from the midrib on the back of the outer part of the lamina.

As epiphytes, all of these bird's-nest ferns should be potted in a very coarse mix with great drainage. They should be under-potted to prevent accumulation of too much moisture although double-potting with the outer pot filled with gravel or the like may be necessary to provide a heavy enough base to support the large fronds. They should be lightly fed at frequent intervals during the growing season. They are very susceptible to snails and slugs and, in San Diego, also to the Giant White Fly.

As explained above, Asplenium nidus is the better known name locally. It is very similar in appearance to A. australasicum but with decided differences. For one, it is truly tropical and will not grow here without the protection of a greenhouse. It is native to northern Queensland in Australia, Christmas Island, east Africa and India. It is, in effect, Old World pan-tropical. The sori extend outward from the midrib but do not cover as much as half the distance to the margin. The most immediately identifiable feature is the shape of the midrib or cross-section that is as in 'a' in the figure with the strong 'keel' on the upper side. If you should acquire on of these plants and can give it the needed protection, you should otherwise treat it as for A. australasicum. Interestingly, there is a variety of A. nidus known as 'Plicatum' or more commonly as the 'Lasagna Fern' which is capable of living here unprotected and which may be found in the local marketplaces. It is much smaller with fairly narrow fronds which are heavily convoluted and pleated.

Asplenium antiguum is smaller that two above and does not form as tight a nest since the fronds taper toward both ends. It has a maximum frond length of about 40 inches and has narrower lamina to perhaps 4 inches. It has about the same hardiness range as A. australasicum but the cross-section of the midrib is different from both of the others having the shape shown in 'c' in the figure, i.e.; rounded both top and bottom. There is a very popular and handsome cultivar of this species that is produced by cloning at Santa Rosa Tropicals and is known as A. antiguum 'Victoria'. This form is fairly small and has many strongly ruffled laminae.

Since our introduction of Asplenium goudeyi to the U.S. market last autumn, we may consider it one of our basic bird's-nest ferns. It is smaller than the big epiphytes and is more often epipetric than epiphytic. It grows in fairly harsh conditions along the cliffs of Lord Howe Island and enjoys a marine atmosphere. Its fronds are stiff and greyish and fairly upright. It may be grown outdoors here in the same manner as A. australasicum.

While researching the information on these four species, I encountered a number of other bird's-nest type ferns that are seldom found in local cultivation, usually because they require special conditions. The following list is by no means exhaustive.

Asplenium cymbifolium. This tropical form from the Philippines, Indonesia, Borneo, Samoa and New Guinea is seldom if ever seen here. It has arching fronds that may be over a meter long and 10 inches wide. The frond bases are broad and dilated so that the rosette may even hold water. I have found no description of the midrib but it is probably shape 'b'.

Asplenium harmonii. This native of south-eastern Queensland is not a true birds'nest by my definition but is considered so by the Australians. It is seldom epiphytic, growing usually on basaltic cliffs, and the rhizome branches to form more than one growing point. The fronds taper to a narrow stem at the base. This results in a very untidy rosette that does not hold things well. Otherwise the plant is like A. australasicum.

Asplenium musifolium. Most modern authors give this plant specific status although some still list it as variety of A. nidus. The two are obviously very similar but A. musifolium has wider fronds to 10 inches and is a very dark green which A. nidus never is. Like A. nidus, this requires a greenhouse locally.

Asplenium phyllitidis. This is native to Singapore and Malaysia. It is similar to A. nidus (no mention of midrib) but has shorter and much narrower fronds that narrow at the base and form a rather poor nest. It is both epiphytic and epipetric and needs a very tropical environment.