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The Honolulu Advertiser
Posted on: Friday, October 24, 2008

HAWAI'I'S GARDENS
Native Hawaiian hau kuahiwi can grow nicely in your garden

By Duane Choy

Whenever I discover unblossomed hau kuahiwi (Hibiscadelphus distans) plants, I make it a goal to return for the experience of the bloom. Historically, the elongated flowers evolved as a nectar-feeding source for our precious Hawaiian honeycreepers.

There are seven known species of Hibiscadelphus, a genus endemic to Hawai'i, but five of those species are now extinct in the wild. One of two surviving wild populations of H. distans lives in the Pu'u Ka Pele Forest Reserve on Kaua'i, in Waimea Canyon above Koai'e stream, where multiple perils lurk everywhere.

Hau kuahiwi is jeopardized by competition from nonnative plants, destruction by introduced herbivores (especially goats), insect predation and human disturbance. The small number of individual plants within a wild population make them severely vulnerable to naturally occurring distress, like hurricanes, landslides, flooding and fire. The limited number of potentially reproductive specimens also equates to a loss of genetic diversity because of the persistence of inbreeding depression.

H. distans is a shrub or modest tree that grows up to 16 feet tall. Plants have a grayish-brown trunk, a graceful branching pattern and wide, heart-shaped leaves with irregular serrated margins. The upper leaf surfaces have fine downy hairs, while the undersides are more densely pubescent. The greenish-yellow tubular flowers are solitary and erect, turning maroon with age. Unlike other relatives in the hibiscus family, these flowers are bilaterally symmetrical. The seed pods are woody capsules, with five sections storing seeds that are yellowish-brown and hairy.

The Hawaiian name hau kuahiwi literally translates to mountain hau, in contrast to the common lowland species of hau (Hibiscus tiliaceus). The Latin name hibiscadelphus means "brother of hibiscus" referring to hibiscus as a fellow member of the Malvaceae family.

Anyone fortunate enough to obtain seeds will learn that hau kuahiwi is easily propagated. Soak the fresh seeds in warm or tap water for 24 hours. The seeds float because their hairs trap air bubbles. Sow them into a medium of three parts perlite or black cinder to one part potting mix, then layer an additional half inch of mix over the seeds. Water them in, then every other day, leaning toward the dry side and not soaking wet. Germination follows in two weeks to three months. Transplant into three- or four-inch pots after four to six true leaves form. Put the potted seedlings in a shady area and repot when plants are twice as tall as their pots. Foliar-feed monthly. Outplant when hau kuahiwi has outgrown a one-gallon pot. Never allow potted plants to become rootbound. The planting site should be in partial sun with well-draining soil. Provide support staking if winds are persistent. Pests include Chinese rose beetles, ants and associated aphids, whiteflies and black twig borers. Use systemic pesticides as recommended.

When I gaze at hau kuahiwi, I visualize native Hawaiian birds fluttering about and feeding upon a true native Hawaiian plant. Hau kuahiwi is a living encapsulation of the ecological glory days of our natural Hawaiian heritage.