The tropical climate of Hawaii supports a diverse range of native plants. The marine influence brings frequent rain but the towering mountains of the larger islands create small dry areas with unique climates. Half of the area in the Hawaiian islands is above 2,000 feet in elevation, which alters the tropical temperature patterns as well. This has led to many different types of tropical plants growing in a variety of weather patterns within a relatively small area.
Hawaiian Tree Fern
The Hawaiian tree fern (Cibotium glaucum) is known in the Hawaiian language as hapu'u pulu. It is the most widely spread of the tree fern species endemic to the tropical Hawaiian islands. It grows on every island, but is most numerous on the Big Island, where it grows in moist rain forests up to an elevation of 5,000 feet. It can grow up to 25 feet tall but usually stays around 10 feet. The fronds can reach lengths of up to 20 feet. They are light green colored on top and blue-white underneath where the spores are produced. The fronds are covered with gold hairs.
The Hawaiian tree fern can tolerate full sun, but it performs better with partial to full shade. It naturally grows as an understory canopy in dense forests and needs to remain moist to wet at all times. They are commonly planted in yards and in public areas all over the Hawaiian islands and adapt well to container culture.
Hawaiian cotton (Gossypium tomentosum) is known in the Hawaiian language as ma'o. It is endemic to all the larger islands in the archipelago except Hawaii. It grows on coastal plains and in dry forests on the leeward side of the islands where rainfall is limited compared to the windward side. Hawaiian cotton is not grown commercially, but the cross breeding with commercial cotton plants (G. hirsutum) has produced pest-resistant hybrids used in production.
Hawaiian cotton grows as a small shrub up to 6 feet tall land about twice as wide. It has three or five lobed leaves about 1 to 4 inches wide and slightly shorter in length that are silver-green. It produces bright yellow flowers that are followed by seed capsules containing fibers we know as cotton. It prefers full sun and needs well-drained soil that does not stay wet. Too much moisture will cause rot to set in. It is not used very often in landscaping but would make a good yard shrub in drier tropical areas if kept well trimmed.
Catchbirdtree (Pisonia umbellifera) is called papala kepau in the Hawaiian language. The sticky sap secreted from the seeds was used like glue by native Hawaiians to trap birds. They would then pluck the bird for the feathers and release them to catch again later. In some cases, they would eat the bird.
Catchbirdtree grows as a large shrub or medium-sized tree up to 50 feet tall. It is found naturally in lowland areas of Kauai and all the larger islands to the east except for Kahoolawe. The leaves are glossy green, oval and 3 to 10 inches long. The flowers are small clusters colored pink-green. The sap-dripping seed pods can be a problem in some landscapes, adhering to clothing insects and birds, often trapping them. It prefers full sun but survives in light shade. It needs a well-draining soil that is allowed to dry out.