Ma‘o (Gossypium tomentosum) – Don’t believe everything you hear – or read. 

    By far, the most difficult part of these webpages for me to write is the ... in Hawaiian Culture section. For the other sections, I am simply detailing my observations and experiences or retelling those of other horticulturists and botanists. Not so with the culture section. 
    Pre-contact Hawaiian culture was largely perpetuated by oral traditions. After Captain Cook’s arrival in Hawai‘i and subsequent visits by other foreigners, large numbers of Hawaiians died from introduced diseases. With their deaths, an unquantifiable amount of Hawaiian culture also died. To make matters worse, for many years, Christian missionaries often persuaded or forced Hawaiians to abandon their old ways.
    People often share with me their understanding of Hawaiian plants. And, frequently, their accounts are both interesting and insightful. Still, I can’t help wondering if what they tell me is ancient Hawaiian knowledge that has survived the last 237 years, or something created much more recently and possibly corrupted by asian or western folklore. Therefore, for the most part, when writing the Hawaiian culture section, I rely on written accounts by well recognized authorities. However, even these have proven to be confusing (see Lonomea) or faulty. For example, Abbott (1992) and Krauss (1993), both legendary Hawaiian ethnobotanists, state that Hawaiians produced a yellow dye for kapa from ma‘o flowers. Superficially, this seems logical; ma‘o flowers are yellow, so, you would expect a yellow dye. There’s only one problem: no one (I know) has been able to verify their claim. Dalani Tanahy is a friend and former coworker. She is also an exceptional kapa-maker (check out her website at: Several years ago, Dalani told me she too had read the accounts of Hawaiians producing a yellow dye from ma‘o flowers and decided to check it out. Her investigation yielded a surprising contradiction: ma‘o flowers yield a bright green – not yellow – kapa dye. This green dye is photosensitive and fades over time which may explain why there are no ancient examples. The moral of this story: Don’t believe everything you hear – or read – about native Hawaiian plants. 

(Top to Bottom) Leaves, flowers, and ripe fruit with seeds. Scarified seed. Wild seedlings near restoration plantings. 
Habitat & Appearance:
Ma‘o is endemic to all the main Hawaiian Islands except Hawai‘i. It was reported extinct in the wild on Kaua‘i in 1992 (National Tropical Botanical Garden) but, with subsequent restoration efforts, it’s unlikely this is still true. It’s naturally found in dry coastal areas or sometimes slightly inland in dry lowlands growing in sand, rocks (calcareous or basalt) or clay. Brushfires and development have eliminated ma‘o from much of its former habitat. Predominately a shrub 2 to 6 feet high, ma‘o is often wider than it is tall. However, there was(is) a treelike variety on Ni‘ihau that grew to ten feet (David Orr, personal communication). Ma‘o leaves are lobed (3 or 5) similar to kukui and maple. Densely covered with soft white hairs, they appear grayish-green. The flowers are light to bright yellow and about 2 inches across. Capsules ripen from green to tan, splitting open to reveal several seeds (¼ inch) densely covered in short reddish brown to tan hairs.  
Ma‘o in Hawaiian Culture: Hawaiians use ma‘o flowers for a bright green kapa dye (see Introduction above). The flowers were also mixed with other native plant parts to make a liquid used for nahu‘aki o ka opu mai na makua mai (gripping stomach ache) (Chun 1994). The fuzzy seeds were likely used in ancient times as medical swaps or coverings. Ma‘o means green as does the word ōma‘o which is also the name of our endemic Hawaiian thrush; this bird has green feathers. An alternative name, huluhulu, is a reference to its hairy leaves. In historic times, ma‘o has been repeatedly hybridized with commercial cotton because it is more disease-resistant and less attractive to insect pests.
Collecting Seeds: Cultivated and most wild ma‘o flower and fruit repeatedly over the year. These cycles are initiated by heavy rains in natural locations. Collect the mature fuzzy tan to reddish-brown seeds directly from dry open fruits. Often good seeds can also be collected from the ground under and surrounding the parent plant. Both viable and inviable ma‘o seeds will float in water because of the air-trapping hairs. Therefore, to separate good from bad seeds allow the seeds to soak in water for several hours and then squeeze each between your fingers. Viable seeds will remain hard while bad seeds will crack and collapse under the pressure. Wash and dry the seeds before storing; in the refrigerator they will remain viable for five or more years. 
Growing from Seed: Ma‘o seeds germinate best when soaked for several hours and then scarified. Do this by firmly grasping the wet seed by its hairs and sanding one area using wet sandpaper. Initially, the sanding will remove the hairs, revealing the dark brown to black outer seedcoat. Sand the seed a bit more in the same spot until the inner dark red seedcoat is visible (see photograph to the right). Do not sand through this inner seedcoat (exposing the cream-colored embryo) because this can damage the embryo, possibly leading to rot. Sow each seed in its own 2 to 4-inch pot filled with any clean, well-drained media, and water daily. The seedlings, with their large speckled cotyledons, will begin emerging from the media in one to two weeks. The first true leaves are triangular, and only later leaves assume the characteristic mature maple-leaf form. Grow the seedlings in full sun or no more than 50% shade to prevent spindly stems and ill-adapted leaves. Dilute liquid or controlled-release fertilizer will hasten seedling growth but don’t overdo it or you’ll attract a host of pests. Ma‘o seedlings are attacked by all the usual sucking insects (e.g., aphids, mealybugs), leaf-boring and leaf-eating insects, as well as, snails and slugs. Refer to Enemies in the Garden for ways to battle these pests. Plants are ready for the garden when they have well-developed bark on their primary stem(s). 
Growing from Cuttings: I have only occasionally grown ma‘o from cuttings because the resulting plants seemed less vigorous than seed-grown ma‘o. Using Method One, rooting takes two or more months. Make very sure there are no pests inside the clear container because they will have a field-day eating your cutting(s). I have never air-layered ma‘o but other horticulturists have reported success.
Growth in the Garden: You should plant your ma‘o in a site with full sun. And, while it’s okay to water the new plant (once a week) for the first couple of months until it establishes a self-sufficient root system, after this, you should stop watering completely or water only during periods of prolonged drought. Generally, fertilizing your ma‘o in the garden will bring more harm than good because it will make it even more attractive to insect pests. Your ma‘o will be 2 to 3 feet in height and breath within a year; twice that in two to three years. Expect flowers and fruits within a year, two at the most. Exercise care in distributing seeds from your ma‘o to friends. As mentioned earlier, ma‘o can hybridize with other non-native cotton plants. If your neighbors are growing these commercial cotton species in their yards as ornamentals or you live near open fields where feral cotton plants may be growing, the seeds you collect from your ma‘o may not be pure. While ma‘o make a poor hedge (in my opinion), they can tolerate moderate pruning. In fact, pruning away stems severely infested with pest insects should be part of its regular care. However, as with any plant, the cuts should be made with a clean sharp blade slightly above a node on the branch. Given the proper environment (i.e., sunny and dry) and protection from pests (see below), ma‘o are moderately long-lived shrubs, lasting ten years or more.    
Diseases & Pests: More insecticide is used on commercial cotton (16 to 25%) than any other single crop (EJF 2007) because it is a magnet to pest insects and diseases. While ma‘o is less attractive, mature plants still get attacked by a host of insects and fungi. Most common are sucking insects like aphids, mealybugs, whiteflies and thrips that tend to aggregate and distort the growing tips. Mites too can be a problem on the leaves. Chewing insects such as grasshoppers sometimes get a taste for ma‘o. Depending on the severity of the infestation, I have ignored the pests and let natural predators control them, pruned off the infested stem-tips, or first pruned and then sprayed the ma‘o with horticultural oil and a systemic insecticide. Often, the sucking insects on your ma‘o are protected and spread by ants. Refer to Enemies in the Garden for ways to deal with ants. Powdery mildew can appear on the leaves of ma‘o during rainy weather, on overwatered plants, or those planted in too much shade. The obvious solutions are to wait until the rains are gone, stop overwatering, and move your ma‘o into the sun, respectively. If the mildew persists, try spraying the plant with a non-systemic fungicide (I prefer the sulfur or copper based ones). A second fungus (Colletotrichum sp.) causes dark leaf spots. Treatment includes removing the infected leaves, stop any irrigation that wets the leaves and can spread the fungus to healthy leaves, and spraying with a broad-spectrum fungicide. Others have reported nematode problems with ma‘o but I have never encountered this, and, therefore, cannot offer any advice.
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