Culture
Winter hardy to USDA zones 10-12 where it grows best in rich, fertile, moist but well-drained soils in full sun. Established plants tolerate drought. Avoid wet soils. Plants are intolerant of frost. Prune as needed to prevent plant from sprawling and to maintain shrub appearance.
Noteworthy Characteristics
Cotton is a staple fiber that develops in a globular pod (boll) around the seeds of cotton plants (genus Gossypium). When ripe, the boll splits open to release the seeds which are embedded in flossy white cotton fibers. The fibers are picked by hand or by machine (harvesters). Cotton seed oil is obtained from crushed seed. Most of the cotton (about 98%) that is commercially cultivated as field crops in the world today comes from two New World species: Gossypium hirsutum, commonly known as upland cotton (90%) and Gossypium barbadense, commonly known as American Pima cotton (8%). Gossypium tomentosum, commonly called Hawaiian cotton or Ma'o, is endemic to Hawaii (only place in the world where it currently grows), but is never commercially grown for harvest of its fibers because those fibers are very short, brown and of no commercial value. On the other hand, Hawaiian cotton plants have good resistance to many of the common insect pests of commercially grown cotton, and, as a result, this species has been successfully crossed with commercial strains of cotton via selective breeding programs for purposes of developing varieties with better pest resistance. Hawaiian cotton is a perennial shrub of the mallow family that typically grows in the wild to 3-6' tall spreading to as much as 7-10' wide. It is most frequently found growing in shrubby, hot, dry coastal areas on all of the main islands in Hawaii except for Kauai and the Big Island. It is threatened in the wild today due in large part to human encroachment and habitat destruction. Plants feature 3- to 5-lobed, maple-like, silver green to gray-green leaves (to 5" diameter) with palmate venation. Bright yellow hibiscus-like flowers (to 2-3" wide) bloom singly or in clusters of 2 or 3 from the leaf axis. In Hawaii, flowers bloom from summer through winter. Flowers are followed by ovoid pods (bolls) which split open when ripe to release the seeds which are embedded in brown fibers.
Genus name comes from the Greek name for cotton.
Specific epithet from the Latin word tomentosus meaning covered with hairs in reference to the cotton fibers.
Problems
In Hawaii, this plant is generally susceptible to chewing and sucking insects. Scale, mealybugs and nematodes may appear. Watch for spider mites. Rots, leaf spot and wilts are potential disease problems.
Uses
In Hawaii, this shrub is sometimes ornamentally planted as an accent or hedge. Trim plants low (e.g., to 2") for use as a ground cover. Xeriscape plant.