Hibiscus clayi

Common Names

Clay's Hibiscus, Red Kauai Rosemallow, Koki’o ʻula, Newhouse Hibiscus

Summary

Clay's hibiscus is a Kauaʻi endemism in the Malvaceae family, a perennial shrub or small tree 4–8 m tall with sparse hairs at branch tips. Leaves are oval to obovate, 3–7 cm long, with upper surface hairless and lower surface slightly hairy, margins entire or serrate toward the apex. Flowers occur singly near branch ends, with dark red petals 4.5–6 cm long; the pale green calyx is 1.5–2.2 cm and pale brown capsules 1.2–1.4 cm long containing about 10 seeds that are brownish black and 4–4.5 mm long.

In cultivation, it prefers full sun with well-drained soils and regular watering, though overwatering can cause yellowing leaves and drought tolerance improves once established. It is grown ornamentally as an accent or hedge and blooms year-round in warm conditions; reproduction occurs by seeds and cuttings, with many cultivated plants remaining as clones via cuttings and cross-pollination with other hibiscus potentially producing hybrids or infertile offspring. Federally endangered and native to Kauaʻi, conservation actions include ex situ stocks and outplantings, and flowers have historic ornamental use and are still used in leis.

Lifecycle

Perennial

Height

13-26 feet

Spread

4-6 ft

Hardiness Zones

Zones 10a-11b

Sunlight Requirements

Ideally full sun; tolerates partial shade.

Soil Type

Well-draining, organic-matter-rich soil with a pH of 6.0–7.0.

Soil Drainage

Well-drained soil

Soil pH

6.0-7.0, slightly acidic to neutral

Bloom Color

Red

Bloom Time

All year round

Foliage Color

Green

Fall Foliage Color

Yellow

Leaf Lifecycle

Evergreen broadleaf

Growth Rate

About 2 ft/year (≈61 cm/year), vigorous growth, doubles in size

Seasons of Interest

Spring, Summer, Fall, Winter

Propagation Methods

Seeds and Cuttings

Attracts Wildlife

Attracts bees, butterflies, other pollinators, and birds (including hummingbirds)