Culture
Winter hardy to USDA Zones 10-12. This is an understory tree fern of shady damp rainforest areas. It prefers moist cool environments in part shade. It tolerates full sun, but may need some shade in the heat of the day, particularly in hot dry conditions. It also tolerates full shade. Best growth typically occurs in tropical to subtropical environments. It is intolerant of frost. It needs protection from strong winds. It can be grown from spores or cuttings.
Noteworthy Characteristics
Cibotium glaucum, commonly known as Hawaiian tree fern or hapu’u pulu, is a slow-growing tree fern that is native to the Hawaiian Islands. It is particularly noticeable on the Island of Hawaii where it is commonly found between 1000’ and 5600’ in moist humid rain forests located on volcanic slopes. This is the most common tree fern in Hawaii. Trunks typically mature to 6-10’ tall, but infrequently to as much as 25’ tall. Mature trunk diameter ranges from 8” to 2’. Fronds mature to 3-9’ long. Arching, 2-3 pinnate compound blades are medium green above and glaucous green below. Yellowish-brown hairs (pulu) cover the petiole bases and bud tips at the trunk ends. Pulu was once harvested and exported to California as a stuffing material for mattresses and pillows, but this practice ended around 1880 when alternate stuffing materials of better quality became available.
Genus name comes from the Greek word kibotion meaning a small box in probable reference to the box-shaped indusia which cover the spores.
Specific epithet from Latin means blue green in reference to the color of the frond undersides.
Problems
No serious insect or disease problems.
Uses
Where winter hardy, this tree fern often grows over time into an imposing and attractive accent or specimen. It should be sited in areas with temperatures which never dip below 40°F, which makes it very difficult to grow outdoors in most parts of the continental U.S. Where not winter hardy, it is best grown in greenhouses.