Ferns were among the earliest plants and evolved millions of years ago. They were a major part of early forests in the days of the dinosaurs and perhaps the first to come back after the great asteroid event 66 million years ago.
Hawaiian gardens have long been famous for their vast array of orchids and other showy flowering plants. Ferns, on the other hand, don’t get top billing in most landscapes even though they were probably the first vascular plants to make Hawaii their home. In fact, ferns have been around long before flowering plants. It is estimated that there are more than 12,000 species today. Most are relatively small but some tree ferns reach 50 or more feet in height. These tree ferns are remnants of the Carboniferous Age and may have existed more than 100 million years ago. The majority of species are found in humid tropical and subtropical regions, but are well represented in temperate forests as well. Ferns may be found growing on rocks, in caves or growing in the tops of trees wherever there is enough moisture and humidity. Ferns growing on other plants, along with orchids and bromeliads, are referred to as epiphytes. We commonly see epiphytotic types growing on hapuu, tree branches and even rocky areas. In the last decade, other “air plants” like bromeliads have become popular because of their colorful foliage and flowers.
Other addition to the list of epiphytes for the small gardens are the staghorn, or elkhorn, ferns. A few species of staghorn, or Platycerium, have grown here for years but are by no means considered common.
Of course, the Platycerium should not be confused with the false staghorn, or uluhe, of Hawaiian forests. This is actually a climbing fern, Dicaranopteris linearis, which can grow into almost impenetrable thickets in the lowland rainforests.
The true staghorn ferns grow epiphytically on support trees mainly in tropical areas of the world. Staghorns come from such places as the Pacific rim, which includes Australia, Papua New Guinea, the Philippines and the Malay Peninsula. Borneo, India, Africa and Madagascar are also represented. One species, Platycerium andinum, comes from Peru and Bolivia. The main species found in the forests of Myanmar is Platycerium coranarium.
Although still plentiful in their native habitat, it has been only within the last 30 years that they have been grown by nurseries here, and some are still considered to be quite rare. Of the 18 species of staghorn ferns, the one most familiar to people is probably Platycerium bifurcatum, which is native to Australia. It has been reported that this species has yielded up to 50 cultivars, or hybrids.
The name platycerium derives from a Greek word meaning broad horn. The word platy means broad and keras means horn, hence, platycerium. This describes the shape of the lower or fertile fronds, which actually resemble a set of stag’s antlers.
All of the staghorn species are members of the fern family. An interesting theory related to the genus Platycerium is that it is considered somewhat of a missing link in the evolution of ferns. When the fern spore germinates, it first develops a flat, shieldlike structure called a gametophyte, or thalli. The fern we recognize develops from this shieldlike structure and the thalli disappears. Because the Platycerium’s basal frond is virtually intact and plays an integral part in its growth habits, it is felt that this basal frond represents a transition between older and present-day forms.
A fossilized spore of Platycerium was identified in sandstone dating to the Cretaceous Period, which supports various theories that this plant family has been around for millions of years, including the era of the dinosaurs. This denotes a heritage of great antiquity. Studies of the genus date back to the early 18th century, when these ferns were first identified in Africa.
Fossil images left in coal deposits 500 million years ago tell us that ferns were the first plants to evolve true leaves. Platyceriums have two distinct sets of leaves. The basal or fertile leaves adhere by root structures to their support. The fertile fronds project outward from a central apex in the basal frond. These fertile fronds can form a dramatic drooping effect, as with the Platycerium bufurcatum and Platycerium coronarium species, or they can be erect, as with Platycerium veitchii.
The fertile frond carries spores in splotches on the underside of the fronds and is a key in some species identification. Platycerium grande is distinguished from a similar cousin, Platycerium superbum, by being smaller. It also has two distinct spore patches on the underside of its fertile fronds, while Platycerium superbum has one large patch. As these fertile fronds grow and mature, they eventually yellow and fall off. The basal fronds play a different role in the plant’s overall function. As they mature, they turn brown and “thatch up” to form a thick matting. This helps protect the stems and roots of the plant and also serves as a “composting” center for the debris that falls into the cavity created by the buildup of fronds. This provides food for growth for this type of epiphytic fern.
Although these spectacular ferns occur most often in tropical areas, many will survive prolonged dry seasons and are quite hardy.
Many cultivars have been developed and there is much speculation about whether any of these have occurred naturally, but the general theory among horticulturists is that they have simply escaped from cultivation and established themselves. This sounds especially feasible considering their antiquity and the interest these unusual plants have generated over the centuries.
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Norman Bezona is professor emeritus, University of Hawaii College of Tropical Agriculture and Human Resources.
