Sweet Potato

Overview

Sweet potato is one of the most useful plants on Kauaʻi. Its vines race across bare soil, shading out weeds and shielding the ground from heavy rain, while giving you edible leaves within weeks and tubers within months. It tolerates drought once established and grows from sea level into the uplands.

History

Sweet potato was domesticated in Central and South America and is now one of the world’s most important food crops. The tubers are a staple food in many countries, the young leaves are cooked as greens, and the vines make good animal feed.

Growing on Kauaʻi

• Grows in all three rainfall zones; on the wet side, plant in raised rows or mounds so tubers don’t rot.
• Prefers loose, well-drained soil. Sheet-mulched beds work well.
• Too much nitrogen gives lots of leaves and few tubers, which is fine if you mainly want ground cover and greens.

Planting and propagation

• Cut 8–12 inch pieces from vigorous vine tips.
• Push them into moist soil or mulch with several leaf nodes buried, leaving the tip exposed.
• Space about 12–18 inches apart for a quick, full cover.
• Water until new growth appears, usually within a week or two.

Care and maintenance

• Pull vines back if they climb young trees or smother small plants.
• Rotate where you dig tubers and replant fresh tip cuttings to keep the patch vigorous.
• Trim overgrown vines and drop them as mulch.

Role in the guild

Sweet potato fills every open space in the starter guild, from the edges of the breadfruit ring to the gaps between shrubs. It acts as living mulch, keeping soil cool and moist while slower plants grow. Pair it with sissoo spinach along the edges.

Harvest

Pick young leaves and shoot tips any time; they are cooked like spinach. Tubers are usually ready about 3–5 months after planting, depending on the variety. Feel around the base and take a few at a time, or dig a whole plant and replant its tips. Cure harvested tubers in a warm, dry, shady spot for about a week to sweeten them and help them store.

Uses

• Food: tubers steamed, baked, or roasted; leaves and tips cooked as greens.
• Soil: living ground cover and chop-and-drop mulch.
• Animal feed: vines are good fodder for rabbits, goats, and pigs.

Problems to watch

• Sweet potato weevil is the most serious pest in Hawaiʻi. Larvae tunnel into tubers and make them bitter. Use clean cuttings from healthy plants, harvest promptly, rotate planting spots, and remove leftover tubers and vines.
• Other pests include leaf miners, hornworms, vine borers, and nematodes.
• Wear gloves when handling slug-damaged plants and wash all produce well; slugs and snails in Hawaiʻi can carry rat lungworm.

General guidance for Kauaʻi; conditions vary by site. Check any new plant at plantpono.org before planting.