Monday | October 24, 2016
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Cotton grown in Hawaii?

Dear Nick, Thanks for your informative column. I live at sea level, not far from the ocean. As an experiment I planted some cotton seeds from a local plant. One plant in particular grew to about 6 feet tall without flowering. Others vary from about 1-foot tall to 4-5 feet, and I see that full sun seems best. I added some fertilizer to the largest plants, and before long I had flowers, yellow ones with red tinges as they matured. Now I have seed pods developing.

On the mainland, I believe that cotton is an annual, and would be plowed under after harvesting the cotton. My plants however have developed 1-inch diameter woody stems and are almost tree like. I have new flowers developing alongside the cotton bolls, so the plant is in different stages at one time.

What should I do after harvesting the cotton? Is it pau once the developing bolls are done? Is there a method of pruning that will keep the plant producing? How often or when should I fertilize? — Thanks, Wendy

The plants are not pau (finished), so the best approach: 1. prune it back but not severely, 2. apply a balanced fertilizer about every six months, and 3. add mulch.

I generally recommend a soil analysis that will reveal if there are deficiencies in the soil.

Cotton is actually a perennial shrub, but growers often cultivate the plants as annuals. In Hawaii, the cotton plant, Gossypium tomentosum or Ma‘o in Hawaiian, is a perennial shrub lasting about three to five years, depending on growing conditions.

Maʻo can be found growing in coastal plains and dry forests primarily on the leeward sides of the main Hawaiian Islands. Ma‘o naturally grows in hot, dry, windy coastal areas tolerating the salty spray. Conversely, it does not do well in locations with continuous high rainfall and in waterlogged soil.

Periodic pruning is necessary to control the height, to keep the shrub full and to prevent low lying branches from spreading.

Back in 1838, a commercial cotton industry was actually started in Kailua on the Big Island. Although it lasted for about a century, cotton never became an important trade item. Even though the fibers were used by early Hawaiians for stuffing pillows, the cotton was not used as a fabric. For more information on Ma‘o, see the website for native plants in Hawaii at

There is also a CTAHR publication titled, “Ma‘o (Hawaiian Cotton).

I use lemongrass in my cooking all the time. The other day I noticed some spots on the leaves and some of the leaves are dying. I’m worried. Are the plants going to die? I need my lemongrass. — Frustrated cook

Lemongrass is a nice complement to the cook’s garden. Unfortunately, this plant is susceptible to a fungal infection known as rust disease. The environmental conditions that favor this disease are high rainfall, high humidity and warm temperatures.

The disease initially begins as tiny yellow spots on the leaves. They merge together developing streaked patterns of brownish, purple lesions running up and down the leaf. Both upper and lower surfaces of the leaf are infected. Wind and rain spread the spores.

The good news is that, normally, the disease is not fatal, but defoliation, poor yields and reduction in oil can occur. In addition, diseased plants are safe to use in cooking recipes.

Here’s what to do:

— Keep plants growing vigorously with adequate fertilizer.

— Avoid planting large numbers of plants together.

— Try growing plants under cover to protect their leaves from rainfall.

— Thin out diseased leaves and destroy the material.

Although the University of Hawaii has not evaluated this fungicide, Trilogy (neem oil) is the only registered material in Hawaii for use against this disease on lemongrass.

Lemongrass is commonly grown by backyard gardeners as an ornamental plant.

It is popular in Thai cooking and other Asian dishes. Leaves can also be dried and use for tea. The lemon-scented oil is used as a fragrance.

Hilo resident Nick Sakovich is a professor emeritus of the University of California. He has worked in the field of agriculture for 30 years. Email your questions to Sakovich at


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