Despite recent rainy spells, it is well-known that our islands are getting dryer every year. This means that periods of drought are getting longer and more frequent. With this in mind, we might want to consider adding some attractive water-wise plants as a way to save water while making our gardens more beautiful. Ma‘o is a lovely native shrub that needs little water.
The silvery-green leaves and bright yellow flowers of the ma‘o, known botanically as Gossypium tomentosum, make it an good looking native Hawaiian member of the hibiscus or Malvaceae family. This family contains over one hundred genera and nearly 2,000 species. Most of them are characterized by a columnar stamen in the center of the flower. Many are native to tropical locations with a few native to Hawaii. The genus Gossypium has a single native Hawaiian species, ma‘o.
The genus name is derived from the Latin word gossypion, which was once the name used for cotton. The cottony seed hairs of ma‘o certainly inspired her genus name, Gossypium. These seed hairs were also the impetus for referring to her as the Hawaiian cotton plant. Though the light brown seed hairs are cottony in texture, they have never been used in textile manufacture.
The relation between this native Hawaiian plant and the commercial cotton plant (Gossypium hirsutum) is close enough, however, that it has offered help to the U.S. cotton crop. Cotton growers used ma’o plants to cross with their plants to improve disease resistance in the cotton industry.
Ma‘o is an endemic native plant meaning that it is native to Hawaii but not native elsewhere. It was originally found growing below 400 feet in elevation on the dry, rocky coastal plains of most of our islands, except the Big Island of Hawaii. Today it is grown as a landscape plant in many tropical locations.
Two forms of ma’o grow well here. The low dwarf is an excellent spreading ground cover that determines at about eighteen inches tall. This form can nicely cover a rocky outcropping or a sunny slope. The shrub form can grow up to six feet tall and can spread to three feet in each direction. It can be used singly as a specimen plant or with others as an unpruned natural hedge.
Each form has leaves that are covered with very short soft white hairs which give them the silvery appearance characteristic of many drought-tolerant plants. The attractive leaves are palm shaped, usually about four inches wide with three to five lobes.
The large bright yellow flowers appear singly and are up to three inches across. Ma‘o plants bloom nearly year-round. Planted in dark soil or black cinder they can be a striking addition to your drought tolerant, native collection.
Traditionally, ma‘o flowers were used to produce a green dye for kapa cloth. Today, the flowers, leaves and seed capsules continue to be used in lei making.
Perhaps, the name ma‘o was assigned to this plant because the word ma’o means green in Hawaiian. If you want to make the dye, you can collect and refrigerate flower petals. When you have enough to proceed, boil them in water to leach out the color. Once you strain the flowers from the mixture, soak cloth in the liquid for several hours until you achieve the color density you want.
The seed capsules that follow flowering produce three to four seeds surrounded by fuzzy beige cotton-like hairs. As they mature the capsules open fully and dry to brown. At this point the seeds are viable and can be planted to produce new plants.
If kept dry, the seeds will remain viable for a long time. Just before planting, however, you need to soak them in warm water for 24 to 48 hours. Though the “cotton” will cause them to float initially, they should sink and absorb some moisture before planting.
Place them about an inch below the surface of a planting mix that is about three quarters perlite to promote good drainage. Place the seeding tray in a shady spot and keep the medium barely moist. Only water when dry, not more than twice a week. Germination can take as long as two months.
Once you have a new plant with four to six leaves, you can pot the seedlings into a larger pot with soil that drains well and a bit of fertilizer. You can up pot again when the seedlings grow tall in about six months. To prepare them for outplanting, gradually expose them to more sun until they are able to thrive in a full sun location.
Ma‘o can also be propagated by cuttings. Use semi-hardwood stems and dip them in rooting hormone before placing in a mix of three parts perlite to one part vermiculite. The cuttings should be adequately rooted and have put out new leaves in two or three months. Treat them the same as seedlings going forward.
Whether you have the low ground cover or the taller shrub ma‘o, you only need to prune to maintain the height and spread you prefer. Fertilizing twice a year is probably adequate for the plant to stay healthy.
Keeping your ma‘o healthy will help it resist pest problems. You can use soap and oil mixes on any sucking insects that might arrive and organic fungicides can treat any fungus that appears. Avoid overwatering the leaves or the soil to prevent rot or other diseases. Ma‘o prefers a dry environment.
Check with Amy Greenwell Garden in Captain Cook to see if they have ma‘o in stock. Other nurseries around the island may also have ma‘o to sell. Call around to find who has them or find one growing and take a few cuttings, with permission of course.
Planning ahead for dry times is wise gardening. Add a ma‘o or two to your garden to prepare for droughts and to add a native Hawaiian beauty.
Gardening events
Ongoing
“Pre-order Leaf Resistant Coffee Trees” from UH CTAHR office in Kainaliu. Catimor hybrid seedlings and grafted trees are available. Conventionally grown, not organic. Trees grafted on liberica rootstock (coffee root-knot nematode-tolerant) are $15/ ungrafted seedlings $10. Available first come, first serve basis. Email andreak@hawaii.edu to express interest. A waiver and release form must be signed prior to purchase.
Tuesday, June 10: “2025 Mango Grower’s Summit” online event from 7:30 to 10 a.m. in Hawaii. Part of Florida State Horticultural Society Annual Meeting.
Register for this free session here: https://tinyurl.com/ykh7y6vh.
Save the dates
Through June 30: “CBB-CLR Pesticide Subsidy Program for 2024- 2025” now accepting applications. Contact hdoa.hawaii.gov/pi/main/cbbsubsidy/ for more information.
July 17-19: “Hawaii Coffee Association Annual Conference” More info at www.hawaiicoffeeassoc.org
Farmer
direct markets
Wednesday: “Ho’oulu Farmers Market” 9 a.m. to 2 p.m. at Sheraton Kona Resort at Keauhou Bay
Saturday: “Keauhou Farmers Market” 8 a.m. to noon at Keauhou Shopping Center
“Kamuela Farmer’s Market” 7:30 a.m. to noon at Pukalani Stables
“Waimea Town Market” 7:30 a.m. to noon at the Parker School in central Waimea
“Waimea Homestead Farmers Market” from 7:30 a.m. to noon at the Waimea middle and elementary school playground
Sunday: “Pure Kona Green Market” 9 a.m. to 2 p.m. at Amy Greenwell Garden in Captain Cook
“Hamakua Harvest” 9 a.m. to 2 p.m. at Hwy 19 and Mamane Street in Honokaa
Plant advice lines
Anytime: konamg@hawaii.edu Tuesdays and Thursdays: 9 a.m. to noon at UH-CES in Kainaliu – 322-4893 or walk in Mon., Tues. and Fri: 9 a.m. to noon at UH CES at Konohana in Hilo 981-5199.
Diana Duff is a plant adviser, educator and consultant living on Oahu and working part time in Kona.