You might want to consider planting a Hawaiian heritage plant that can add an attractive ground cover that is good for your garden while providing an edible staple that is good for you. Known in Hawaii as ‘uala, Hawaiian sweet potatoes were such an important part of a healthy diet that early Polynesians brought them with them when they first settled here in the 6th century.
Sweet potato farming soon became quite extensive and ‘uala served as an important part of the Hawaiian diet. It is a truly functional food, rich in vitamins and minerals. The tubers are loaded with dietary fiber and the leaves can be eaten both raw and steamed.
Known botanically as Ipomoea batatas, Hawaiian sweet potatoes are in the Convolvulaceae or Morning-glory family which obviously includes the morning glory vine as well as the well-known ornamental blue daze.
The ‘uala flower is similar to the tubular morning glory flower and ranges from white to light lavender in color usually with a darker throat. They can be up to 2.5 inches across when fully open. Most of the flowers open in the early morning and usually close by early afternoon.
Several different sweet potato cultivars exist which explains the color range of the flower as well as the variety of leaf colors and shapes. Leaves range in color from light to dark green and purple tinged to almost black. They may be heart shaped, lobed or deeply lobed, nearly palmate in shape.
The root may also vary in color depending on the cultivar. ‘Uala tubers are long and tapered with light brown skin and purple flesh that deepens in color when cooked. Though the Hawaiian sweet potato is usually purple inside others exist with orange or white flesh. All are sweetly delicious and are excellent ingredients for a variety of dishes.
Recipes abound for using the tubers steamed, boiled, mashed or in soups, stews and curries. They are also excellent in salads and are delicious in desserts including cakes and pies. Look for ways to prepare this wonderful root crop on the web or in local cookbooks.
At the Hawaii Ulu Cooperative in Captain Cook, you can get information about preparing the Hawaiian sweet potato and buy recipe ready ‘uala. Give them a call to check on availability at 808-322-3064.
Of the several varieties of sweet potato grown in Hawaii the purple, known as the Okinawan sweet potato, is a good choice to plant. The leaves will add interest to your garden and the tubers will make a colorful addition to many recipes. You can also eat the tender young leaves either raw or steamed.
According to a UH CTAHR publication ‘Rapoza’ is the variety with whitish skin and purple flesh that grows well in Kona and other drier locales.
Ipomoea batatas are best propagated from cuttings. Start with a piece of stem about 12 inches long with at least 3 to 4 nodes and bury it in moist soil. Plan for hilling and circling the stems when determining planting distances. It is important to keep the soil moist early in the life of the plant. Supply the young plants with regular watering intervals (perhaps twice a week).
Though the tubers can be used as ‘seed’, many that are in the stores are irradiated and will not sprout. Best to get tubers from a farmer and suspend them in a glass of water with only half of the tuber under water. It should begin sprouting in a few weeks. When reliable tubers are not available, vegetative cuttings are the best means of propagation.
The best place to get vegetative starts is from a farmer or friend who has healthy plants. You may occasionally find them in local nurseries or at Amy Greenwell Ethnobotanical Garden. Call first to check on availability.
When successfully rooted, sweet potatoes are relatively drought tolerant though the leaves may wilt slightly in hot dry weather. Once the plant begins to grow it’s important to keep it off the ground so that it doesn’t root at every node, which will produce more potatoes but of a smaller size. Keeping new stems off the ground by circling them will prevent random rooting, will save space and help larger tubers to form.
The plants will thrive in full sun in a deep, friable, well drained, slightly acidic soil. The ideal growing medium is a soil with a pH between 5.5 and 6.5. Water several times a week when the plants are growing but stop watering about a month before harvest.
Tubers can be harvested once the plant has flowered, usually about 4 to 6 months after planting. They will get large and woody and perhaps infested with weevils if left in the field too long.
Once harvested, tubers benefit from curing. Curing is best done in a dry, well-ventilated area for about a week with temperatures in the mid 80’s. Storage after curing should be in a well-ventilated area with temperatures near 60 degrees. Cured potatoes can be stored up to 7 months.
Fertilize your sweet potatoes with a product containing nitrogen, phosphorus, and adequate potassium for optimum root growth. High nitrogen levels can cause excessive vine growth at the expense of root yields and may result in root cracking. Potassium is the most important nutrient for proper tuber production.
Though several pests regard sweet potatoes as host, the life of healthy plants is seldom threatened by insect or disease attacks. The best prevention of disease is to change the location of your sweet potato plants each time you plant.
The most serious insect pests are weevils and beetle grubs that will bore into the tubers. These can be avoided by practicing crop rotation. Beetles, caterpillars and stem borers may cause some damage to the plants but do try to positively identify any pests before proceeding to find the least toxic means of control.
Growing attractive edibles like sweet potatoes can enhance your garden’s appearance as well as its benefits. Consider growing plants like sweet potatoes that serve double duty in your landscape.
Gardening events
Now: 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 on a first come, first served basis. Email andreak@hawaii.edu to express interest. A waiver and release form must be signed prior to purchase.
Wednesday, Dec. 11: “Branding and Messaging for Your Small Business” Webinar from 10 to 11:30 a.m. Also Check out Hawaii Small Business Development Center’s other Live Webinars go to clients.hisbdc.org for more information or to register for these:
Dec. 18: Tax Planning for Your Small Business
Dec. 18: Starting a Business in Hawai‘i
Thursday, Dec. 12: Grow Aloha: Nurturing Biocultural Connections One Plant at a Time. Arrive at 5:30 p.m. talk begins at 6 p.m. David Bryant, director of communications at the National Botanical Garden, will speak at Hale Pulelehua at Amy Greenwell Ethnobotanical Garden, 82-6160 Mamalahoa Hwy (please park at the Garden Visitor Center and walk in). Ethnobotanical Pupu Potluck follows the talk. RSVP to info@amygreenwell.garden by Wednesday, Dec. 11.
Save the date
Tuesday, Feb. 25: Coffee Symposium and Trade Show at the Outrigger Kona’s Kaleiopapa Conference Center with the Trade Show immediately adjacent. Sponsorships and registration available at the Kona Coffee Farmers’ Association website.
Farmer direct markets
(Check websites for the latest hours and online markets)
Wednesday and Friday: 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. – 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 or himga@hawaii.edu
Diana Duff is a plant adviser, educator and consultant living part time in Kailua-Kona.