How to grow Kang Kong in New Zealand
Kang kong, also called water spinach or ong choy, is a fast, heat-loving leafy green with hollow stems and long, bamboo-shaped leaves, much used in Southeast Asian stir-fries and soups. It grows in very moist soil or even shallow water and crops cut-and-come-again for weeks. In New Zealand it is a summer crop for warm northern gardens, tunnel houses and pots on sunny decks.
📖 Our full guide: How to Grow Kang Kong in New Zealand
At a glance
When to sow by region
| Region | When to sow | Regional note |
|---|---|---|
| Northland | September to December | |
| Auckland | September to December | |
| Waikato & Bay of Plenty | October to December | Needs warmth and very moist soil. Sow Oct to Dec once the frosts are over. |
| Central North Island | December | Needs warmth. Grow it in a tunnel house or a pot on a sunny deck. |
| Wellington & Lower North Island | November and December | Needs warmth. Sow Nov to Dec in a warm spot out of the wind, or grow it in a tunnel house. |
| Nelson & Marlborough | November and December | Needs warmth. Sow Nov to Dec in a warm sheltered spot, or grow it in a tunnel house. |
| Canterbury | December | Needs warmth. Grow it in a tunnel house or a pot on a sunny deck. |
| Otago & Southland | December | Needs warmth. Grow it in a tunnel house or a pot on a sunny deck. |
| Central Otago | December | Needs warmth. Grow it in a tunnel house or a pot on a sunny deck. |
Where to plant
Kang kong needs heat, full sun and constant moisture. Grow it in rich, moist soil that never dries out, in a bed that stays damp, or in a pot or tub sitting in a tray of water. It germinates best in soil of 25 to 30°C and sulks in cool weather.
It fills the summer gap when spinach and lettuce bolt, and is at its best in the hottest months.
- Northland and Auckland: sow from September to December once nights are warm.
- Waikato and Bay of Plenty: sow from October to December once the frosts are over.
- Wellington and Nelson and Marlborough: sow in November and December in a warm spot out of the wind, or grow it in a tunnel house.
- Central North Island, Canterbury, Otago and Southland, and Central Otago: grow it in a tunnel house or a pot on a sunny deck, sown in December.
How to plant
- Wait until the weather is consistently warm. Soaking seed overnight can help speed germination.
- Sow seed direct about 6 to 15 mm deep into moist, rich soil, about 15 to 20 cm apart in rows 30 cm apart. Seed germinates in 7 to 14 days in warm soil.
- Alternatively, sow in pots in a warm spot and plant out once nights are warm.
- Keep the soil wet at all times. In a pot, stand it in a saucer or tray of water.
Watering and feeding
Consistent moisture is essential. Water often enough that the soil never dries, or keep the base of the pot in water. Dry plants turn coarse and stringy.
Feed every week or two with a liquid fertiliser high in nitrogen for fast, tender leafy growth.
Harvesting
Start cutting about six to ten weeks after sowing, when shoots are about 25 to 30 cm long. Snip the tips just above a leaf joint; the plant branches and regrows, so you can cut again every couple of weeks through summer.
Use both the hollow stems and leaves. Kang kong wilts quickly once picked, so use it within a day or two, kept in a damp cloth in the fridge.
Growing in pots
Kang kong is ideal for pots. Use a pot at least 25 cm wide with rich potting mix, stand it in a tray of water in full sun, and feed regularly. In cooler districts a pot on a hot deck or in a tunnel house is the most reliable way to grow it.
Varieties
- Land Kangkong (Upland)
Pests and diseases
Kang kong has few problems in New Zealand gardens. Cool weather slows it more than pests do.
Pests to watch for
- Aphids Clusters on the shoot tips and young leaves.
- Leaf miner Pale, winding trails in the leaves.
Diseases to watch for
- White rust White, blister-like pustules on the underside of leaves, with yellow patches above. Remove affected shoots.
Common questions
Is kang kong the same as water spinach?
Yes. Kang kong, water spinach and ong choy are names for Ipomoea aquatica, a relative of sweet potato grown for its leafy shoots.
Does kang kong need to grow in water?
No, but it does need constantly moist soil. It grows well in a wet bed or a pot standing in a tray of water, and in shallow water.
Can I grow kang kong in the South Island?
Yes, in a tunnel house or a pot in a hot, sunny spot. Sow in December, when it is warm enough, and keep it wet.
How do I harvest kang kong?
Cut shoot tips about 25 to 30 cm long, just above a leaf joint. The plant branches and regrows, so keep cutting every couple of weeks through summer.
Why is my kang kong tough?
Shoots turn coarse if the plant dries out or is left too long between cuts. Keep it wet, feed it, and pick regularly while the stems are tender.
Sources we checked: Kings Seeds NZ: Water Spinach Bamboo Leaf; Wikipedia: Ipomoea aquatica.