I recently caught sight of the blooms of a candlestick plant (Senna alata) in my neighborhood and was reminded that this plant in the Fabaceae (bean) family has an equally attractive relative that is a native Hawaiian plant. ‘Ohai is not invasive and thrives here. For those of you with a dry coastal site, the endemic ‘ohai (Sesbania tomentosa) might be a great addition to your garden.
‘Ohai grows on all of the Hawaiian Islands from the coastal shoreline up to 2,000 feet. Though the low growing tomentosa does well near the coast, many different forms are available. Some will mound to 5 feet tall and spread to 10 feet wide. More upright and shrubby varieties are also available but they tend to be spindly. None of these Sesbania varieties like much rainfall or the heavy soils in areas like mauka Kona.
The recumbent variety can cover the ground up to ten feet from the main stem and rise to eighteen inches or less. The sprawling appearance can attractively fill an open space in your garden and even cover rocky outcroppings. The upright plant can grow to be a shrub or even tree-like in habit.
Both species have small oval leaflets that branch off a central rib giving the leaves a feathery appearance. The leaflets are covered with tiny hairs that gives them a silvery appearance. This protects them from the sun’s harsh rays allowing them to thrive in full-sun hot spots.
Once plentiful in dry locations on all of the islands, habitat destruction has severely diminished ‘ohai’s natural occurrence and it is now considered an endangered plant. Though historically known as a lei plant, it is rarely found in the wild or in lei, today. ‘Ohai now relies heavily on cultivated specimens for its continued existence.
‘Ohai’s flowers are reminiscent of other bean family blossoms. The pea-shaped flowers hang in clusters below the foliage with two to five per cluster. Though often a bright red-orange, some specimens flower in lighter colors like salmon or yellow. The leaf and flower colors of the ‘ohai varieties make this plant an attractive addition to a hot, dry space.
Once pollinated, the flowers develop tan fruit pods that contain as many as twenty olive-brown seeds. ‘Oha’s seeds can be easily collected from the dry pods and used for propagation. They can be kept dry and refrigerated for several years but germination rate may fall over time. For best results, it is recommended to use the seeds soon after harvest.
Propagating ‘ohai from seed is fairly simple. Carefully scarify the small seeds with a nail-clipper or sandpaper immediately before sowing or soak them overnight. Sow in a media mix that holds some moisture but drains well. Potting soil mixed with perlite in seeding trays works well. The first seeds should sprout in about two weeks and continue for another month.
Once they begin to put out new leaves, you can transfer them to a larger pot placed in a sunny spot. The seedlings will grow at a moderate rate and be between 6 and 12 inches tall within six months. At this point, you can transfer them to your garden or into a more permanent container.
You can also propagate ‘ohai from semi-hardwood cuttings. Choose a strong, non-flowering stem and cut a piece about six inches long. Remove the lower leaves and dip the cut end into a rooting hormone. Place the cutting in a pot containing a potting mix that drains well and keep the soil moist. A mix of 50% perlite and 50% vermiculite works well. When the cutting puts our new leaves and feels solidly rooted, you can follow the same procedure at that used for seedlings.
Be sure to place ‘ohai plants in an area that gets full sun most of the day. Avoid planting them in dense clay soil that may hold too much water in the root zone. These plants can grow in poor soil or sand, as long as it drains well.
Because ‘ohai are nitrogen-fixing plants, they will provide a natural source of nitrogen for themselves and will enrich the soil with nitrogen for other plants growing around them. They require very little fertilizer and water and only need pruning to control size and shape.
Gardeners challenged with hot dry locations at the coast will be especially happy to learn of ‘ohai’s tolerance of wind, salt, heat and drought. For those challenged with hot, dry coastal locations, this plant is an excellent choice.
In addition to its gardener-friendly tolerances, ʻohai also offers several attractive features. The leaves can add an interesting leaf texture to the landscape while the flowers add color. Some even give off a nice citrusy scent from their leaves on hot, sunny afternoons. The prostrate forms can be used to fill in areas where other plants may not grow. The shrub forms can be used as accents or hedges, and the tree forms can serve as a tall hedge or as screen plants.
All do well in pots with good drainage and in full sun. Just be sure tall varieties are secured against toppling in strong winds. To prevent root rot, avoid over watering by allowing the soil to dry between waterings.
Mealy bugs, aphids and white fly may attack unhealthy ‘ohai. This can lead to black sooty mold on the trunk, twigs and leaves. A soap and oil mix can control the insects and a soapy wash of the leaves will remove sooty mold. Though soil nematodes can cause root problems, several deterrents are described only to prevent their damage.
On Oahu, the black stink bug (Coptosoma xanthogramma) has been found on ‘ohai. This invasive pest feeds on many legumes but is not yet widespread on the Big Island. invasive pest, feeding on legumes and similar plants. They can be controlled with neem oil and/or Spinosad. Follow the directions on the product or check online.
Including native Hawaiian plants in your garden that are well suited to our climate and growing conditions can avoid problems that might arise from plants not accustomed to life here. It is also a good deed for the preservation of native species. Planting ‘ohai will reward you with a lovely plant that has many tolerances and features.
Check with Margo, formerly of Sunrise Nursery. She’s at (808) 640-9191 and may be able to help you find ‘ohai plants or seeds.
Gardening Events
Saturdays: Work Day at Amy Greenwell Garden from 9 a.m. to 12:30 p.m. Meet at the Garden Visitor Center across from the Manago Hotel in Captain Cook. Come with a mask and be prepared to practice social distancing. Volunteers can help with garden maintenance and are invited to bring a brown bag lunch. Water and snacks provided.
Tuesday, April 8: Easy Way to Business Bookkeeping: Paper &Excel from 10 a.m. to 11:30 a.m. online. Facilitated by Hawai‘i SBDC, West Hawai‘i Center. Fee $15. Go to clients.hisbdc.org to register.
Thursday and Friday, April 10 to 12: Cirque de Chocolate — 12th Annual Big Island Chocolate Festival at the Waikoloa Beach Marriott Resort &Spa. Thursday will feature farm tours including the Original Hawaiian Chocolate Factory. Agricultural seminars will be held on Friday. Some chocolate themed culinary demonstrations will take place on Saturday followed by an evening galla. Tastings at savory and sweet culinary booths will be part of the festivities as well as a chocolate fountain, DJ dancing and a silent auction. Go to https://bigislandchocolatefestival.com for a complete schedule of events and to buy your tickets.
April 1 to April 30: Hawaii Coffee Cupping Competition Registration. Entry fee $100 per sample. Cupping is May 27 – 30 in Texas. Winners announced July 18, at the HCA Annual Conference. Go to cdn.wildapricot.com for entry guidelines and procedures.
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 served basis. Email andreak@hawaii.edu to express interest. A waiver and release form must be signed prior to purchase.
Save the Dates
Saturday, May 3: Mother’s Day Orchid Show from 9 a.m. to 2 p.m. at Makaeo Pavilion at Kona Old Airport State Recreational Area. The 40th anniversary of the Kona Orchid Society annual Plant &Craft Sale. Admission is $2 cash and the first 300 attendees will receive a free orchid plant. Go to konaorchidsociety.squarespace.com for more information.
Saturday, May 10: Hilo Chocolate Festival from 9 a.m to 4p.m. at the Hilo Hawaiian Hotel, Maku‘ola Ballroom, 71 Banyan Drive in Hilo. Farm tours, chocolate vendors with samples, educational demos and displays, silent auction. Free to the public. Go to www.easthawaiicacao.org/festival for more info.
Thursday, May 17: World Bee Day from 10 a.m. to 3 p.m. at the Makupapapa Discovery Center, 76 Kamehameha Avenue, Hilo. Crafts, cooking demos, beekeeper talks. Free. For more information email: worldbeedayhawaii@gmail .com or text 808-936-6019.
July 17-19: Hawaii Coffee Association Annual Conference at the Outrigger Kona Resort. Registration now open. More info at www.hawaiicoffeeassoc.org
Farmer Direct Markets
Wednesdays and Fridays: Ho‘oulu Farmers Market, 9 a.m. to 2 p.m. at Sheraton Kona Resort at Keauhou Bay.
Saturdays: 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.
Sundays: 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 Friday: 9 a.m. to noon at UH-CES at Konohana in Hilo, 981-5199 or himga@hawaii.edu.
This article has been reviewed for accuracy by Peter VanDyke, former director of Amy Greenwell Garden
Diana Duff is a plant adviser, educator and consultant living on Oahu and working part time in Kona.
