Hawaiian cotton, or mao, grows well near the shore

Every day, people around the world wear clothes that carry the plant genes of mao (Gossypium tomentosum), our endemic Hawaiian cotton, also called huluhulu.

It’s not the cotton fibers of mao that are woven into these garments — it’s mao’s DNA that is crossed through cotton-breeding research to generate flowers without nectaries (glands that secrete nectar) to minimize insect damage on commercial cotton crops. Studies are further being conducted on crossing mao for hybrid enhancements on fiber quality and yield, disease resistance, and tolerance to drought and heat.

Mao is a coastal shrub that thrives from sea level to about 390 feet in elevation, usually in residual fragments on the leeward side of our Hawaiian islands. Tragically, mao is now considered extinct in the wild on Kauai.

Enduring salt spray, drought, wind, full sun and sweltering temperatures, mao will grow in sand, seasoned clay and rock substrates. Mao abhors excessively wet environments.

It’s a low, sprawling shrub that can evolve into variable, widespread clumps. The three- to five-lobed maplelike leaves are rounded or pointed at the tips. Branched hairs on the leaf surface evoke a silvery gray-green image. Year round, profuse blossoms are luminous lemon-yellow, emerging either solitarily or in clusters of up to three flowers.

The fruit is a woody three-part capsule. Six to 12 seeds, coated with reddish-brown lint (cotton fiber), are on the boll.

Hawaiians extracted a yellow dye for kapa cloth from the flower petals and a greenish dye from the leaves. Lei of lustrous mao flowers mimic ilima on yellow steroids.

Early Hawaiians never used mao as a fabric, but did use the cotton as pillow stuffing. Also, the fibers provided a medium — like modern-day cotton balls and swabs — for medicinal application. For "nahuaki o ka opu mai na makua mai" (gripping stomachache, as in childbirth), mao blossoms and the bark of its tap roots were crushed, infused with other botanicals, heated and then swallowed as a liquid.

Mao’s textural, ornamental leaves and alluring, ravishing flowers offer superb landscaping options in xeriscape gardens and the difficult coastal growing zone. Design mao as an integral component in shrub composition, broad ground cover, or shallow hedge planting. Pruning establishes proper volume and texture.

The Center for Plant Conservation reports on its website: "The Ma‘o, or Hawaiian cotton … has been so reduced by seaside development and habitat destruction that it is now vulnerable to extinction."

Mao became homeless in the wild on Kauai. Let’s resolve to never repeat this botanical catastrophe in our beloved Hawaii.

Duane Choy is a native Hawaiian plant specialist. Reach him at HanaHou@ecologyfund.net.