A common mistake made in Hawaii is to attempt to grow plants where they are not adapted. This is complicated with weather changes occurring not only with melting glaciers in the Arctic or typhoons in the Philippines but with extensive drought conditions here at home. Last year was a dry one and this year has been even worse. Statewide, it is one of the driest years in more than a century of keeping records. In East Hawaii, rivers have all but dried to a trickle and in West Hawaii, drought tolerant kiawe and haole koa appear all but dead. In the cloud forests of upper Kona, hapuu tree ferns are withered and dying. Some are well over 100 years old.
The scientific name of our common tree fern is Cibotium glaucum. The common names are hapuu and Hawaiian tree fern. They are native to most mountainous islands in Hawaii. These descendants of an ancient type of vegetation are found in semi-wet to wet forests from sea level to 5,000 feet elevation.
Tree ferns, though, are often used in the wrong place. For many years, it has been common practice to go to the rain forests and cut down hapuu for instant landscaping, or to chip for orchid media. Today, these beautiful ferns are threatened because they are very slow growing, and in most areas, grow only 2 to 3 inches of trunk per year. When removed from the forest, weeds often take over the exposed area. An example is in Kaloko Mauka, where tree ferns 20 years ago covered most of the roadside from the highway to the top of Kaloko Drive. Today, invading weeds are encroaching where people have illegally cut down the hapuu, bulldozed or allowed grazing animals access to hapuu stands.
Overexploitation and drying conditions because of climate change have reduced the once-common hapuu stands drastically.
Pulu was used in ancient times for dressing wounds and for embalming. It has been used for stuffing pillows and mattresses. Until recently, large numbers were cut for orchid media and landscape use. Trunks cut and planted in less than ideal locations live for a while, then gradually decline and die, thus requiring frequent replacement.
Presently, all tree ferns are considered threatened since most species are found in the rapidly diminishing rain and cloud forests of the world. It is illegal to ship tree ferns or tree fern products internationally. This does not protect tree ferns within a country from destruction.
The last remaining large stands of hapuu are found primarily on the Island of Hawaii, however, these are being rapidly reduced by clearing and development except in protected areas.
The leaves of hapuu ii, another less common native Hawaiian tree fern, sport a thick growth of stiff, blackish hair on the petiole. This native tree fern is also slightly taller and has stiffer fronds. Otherwise, the two species of hapuu are similar in appearance. Hapuu ii seldom survives transplanting and is rarely used in the landscape.
Tree ferns are excellent as small trees. They are especially pleasing as specimens to create a tropical effect in a landscape or garden.
Unfortunately, the Hawaiian tree fern is becoming scarce, so should only be planted where garden conditions are ideal, such as wetter areas with well-distributed rainfall. Do not remove hapuu from the forest without proper authority. Because our islands seem to be getting drier, it would be better to landscape with more drought-resistant trees and shrubs.
There are many species of tree fern that are relatively easy to grow and reasonably tolerant of a variety of conditions. However, none are presently available in the nursery trade. The Australian tree fern, Cyathea cooperi, was at one time readily available but is now on the list of invasive species since it is one of the few that tend to naturalize in some situations. Others, such as the Puerto Rican, Costa Rican and Fiji tree ferns, are found in some botanical gardens but are not usually propagated.
If you are fortunate enough to get one of these species, give it a try in your garden. They prefer well-drained soil in partial shade, but will tolerate full sun in cloudy, mauka areas or in well-watered landscapes. Tree ferns will need protection from the sun and drying winds in hot, sunny lowlands. They prefer slightly acidic soil. Tree ferns benefit from a steady supply of water with good drainage. Fertilize occasionally with light applications of a complete fertilizer containing slow-release nitrogen. Organic sources are preferred. Avoid quick-release chemical fertilizers since they may actually burn the fern. Prune out old and injured fronds, as necessary.
Insects and diseases are few. If you are interested in propagation, the side shoots can be removed to produce new plants. Tree ferns may also be started by spores, but this takes patience and time.
This information is supplied by the University of Hawaii College of Tropical Agriculture and Human Resources. For more information on fern culture, contact the nearest office.
