Spring in Kona’s unique tropical cloud forests and East Hawaii’s rainforests is heralded by abundant new growth of ferns, especially our endemic cibotium treeferns. If you want to get a sense of what life was like during the time of the dinosaurs, visit the Kona Cloud Forest above Kailua. The area abounds with ferns that once were dominant millions of years ago.
Hawaii Volcanoes National Park is also another region famous for forests primarily composed of our native cibotium or hapu’u, sadleria or amaumau ferns and ohia. During the pandemic lockdown, many folks take advantage of the peace and beauty of the forests to walk and watch for native birds attracted to the Ohia lehua. This year, volunteers sponsored by Old Navy are helping to beautify the Kona Cloud Forest Sanctuary area roadsides and trails along Hao Street and Kaloko Drive as well. Money received for their work is being donated to the Project Hawaii To Fund Homeless Keiki Easter Baskets. To get more information on the project and how to help, check out http://www.helpthehomelesskeiki.org. You may also contact Kym Gentry Peck at kymgpeck@gmail.com or call her at (808) 494-5193.
As you experience our upland forests, take note of the many types of ferns. Ferns are a good example of a whole family of plants that are not often represented in our gardens. It’s not that they can’t be grown, but that we don’t give them much of a try. Ferns, in general, are free of insect and disease problems. They require very little fertilizer but do require moisture and shade from intense sunlight. Our cooler mauka areas are probably the best for growing ferns, but many types may be grown almost anywhere with protection.
We have hundreds of ferns native and introduced to Hawaii, but this is just a fraction of the more than 9,000 species found throughout the world. Members of the fern family vary from moss like mini ferns to gigantic palm like tree ferns over 40 feet in height. There are many ferns that live attached to trunks and branches of trees like the native Bird Nest Fern, Asplenium nidus, and the Austral Asian staghorn ferns, platycerium species. Most ferns prefer those shady, moist locations but some species will take full sun, so there is a spot in your garden for at least one or two types.
A side benefit of ferns is that some are edible. Some examples are the swamp Fern and “warabi.” The swamp fern, Ceratopreris thalictroides, found growing wild in moist areas may be eaten either raw or cooked as greens. Our native treefern or hapu’u, has an acrid substance so strong that the new leaf “fiddle” must be boiled outside for 30 to 45 minutes since they contain irritating fumes. After boiling, the outer skin is peeled off and the interior portions are soaked in fresh water. The water is discarded and replaced with fresh water each day. This procedure takes three to four days. Then they may be stored in the water and refrigerated for several months. Fern shoots add an exotic touch to vegetable and pork dishes along with bamboo shoots. Many edible ferns like the Arythrium esculentum of Southeast Asia are also high in Vitamin A.
In the landscape, ferns give a lush rainforest effect. They give that ultra tropical look that really makes a garden special. The most striking effect, by far, is created by the treefern types. We take our native hapu’u for granted, but in other parts of the world, different species are in great demand as landscaping plants.
In Hawaii, our native Cibotium are being used in the landscape but are slow growing and are becoming scarce. The hapu’u ii or male fern usually dies after transplanting. The so-called female fern may be transplanted before new leaves emerge in the spring, but often die when planted out of their natural wet habitat. To establish them, plant in a rich organic soil and keep them moist and shaded. Within a couple of weeks, they will begin developing large airy leaves and roots. A shady spot protected from wind is best. They should be watered on the trunk and at the base frequently. Live stumps may sometimes be purchased locally. Do not remove ferns from the forests. It is illegal without permission. They are becoming rare in some areas due to cutting and removing.
Some other species of treeferns are carried in a few local nurseries. These include types from Central America and the Caribbean, Southeast Asia and Australia. Cyathea cooperi is not recommended as it naturalizes readily when conditions are ideal, but there are at least a dozen other species that do not naturalize easily. They are well adapted here and are fairly fast growers. Under good conditions, they will produce fronds higher than your head in a year or so. With room, they will form a trunk to 10 feet or more. These species are more tolerant of sun and dry conditions than our native hapu’u.
In cooler locations, the New Zealand treeferns, Dicksonia antarctica, D. squarrosa and Cyathea medullaris, do very well. Here again, shade and moisture are the keys to success.
There are many other types of treefern types available including the Mexican Blechnum, which is a miniature type to about 3 feet. This is available at garden stores and some nurseries.
Cibotium schiedei, the true “Mexican treefern,” is of very slow growth and rarely seen with a trunk outside its native habitat in the mountains of Chiapas and Vera Cruz. This graceful fern is usually grown in tubs. With its pale green, showy fronds, it has become a favorite of florists, for weddings and other formal occasions. Although popular in Southern California, few are found locally.
When planting ferns, be sure to enrich the planting sight by adding peat moss or rotted compost and some well-rotted manure to the existing soil. A good ratio is about 50% peat, 40% cinder, and 10% well-rotted manure. New plants should be watered daily until they are established.
Ferns are sensitive to chemical fertilizers so use them sparingly. It is better to use organics like sewage sludge or rotted manures. Fertilize about once every two to three months for best growth. Avoid liquid insecticides and fungicides for they too will burn. Diluted wettable powders are safer. Ferns are extremely susceptible to herbicides, so be careful.