Nasturtiums: The Secret Super Plant Every South African Garden Needs
How to grow Nasturtiums from seed in South Africa
Applies to: Alaska Mix, Baby Red, Climbing Single Mix, Globe of Fire, Golden Globe and Jewel Choice Mix.
Nasturtiums are quick, cool-to-mild-season annuals with edible leaves and flowers when grown without unsuitable pesticides. They flower best in full sun and modest soil. Overfeeding—especially with nitrogen—creates abundant leaves and few flowers.
Quick sowing guide
| Field |
Recommendation |
| Seed depth |
10–20 mm; about 15 mm is a dependable target |
| Germination |
Usually 7–14 days at 16–18 °C |
| Light after emergence |
Full sun; light afternoon shade in very hot districts |
| Compact/trailing spacing |
25–30 cm |
| Climbing Single Mix spacing |
30–45 cm, beside a trellis or fence |
| Sowing method |
Direct sow preferred; deep cells are suitable for transplants |
Choose the correct growth type
Compact or trailing Nasturtiums
Alaska Mix, Baby Red, Globe of Fire, Golden Globe and Jewel Choice Mix. Alaska and Jewel Choice spread attractively over bed edges and containers; Baby Red and the Globe types are more compact.
Climbing Nasturtiums
Climbing Single Mix can reach about 2 m. Provide netting, wire or twiggy support at sowing time and guide young stems onto it.
Sowing and planting
- Sow into moist, free-draining soil at the final spacing. Place one or two seeds per station, 10–20 mm deep.
- Keep evenly moist until emergence, then thin to the strongest plant without pulling against neighbouring roots.
- If using trays, choose deep cells and transplant young, before roots circle. Harden seedlings first.
- Do not soak treated seed. For untreated seed, soaking is optional rather than necessary; consistently moist soil is safer than prolonged soaking.
Ongoing care
- Water deeply, then allow the upper soil to begin drying. Containers need more frequent checks.
- In ordinary garden soil, little feeding is required. Avoid lawn fertiliser or manure-heavy beds.
- Deadhead to extend flowering, or allow a few flowers to set seed at the end of the display.
- Check leaf undersides for aphids and cabbage-butterfly eggs or caterpillars. Nasturtiums may attract pests, but they are not a guaranteed “trap crop”: inspect and manage them so they do not become a pest reservoir.
- Powdery mildew is more likely on drought-stressed or crowded plants. Improve airflow and water the root zone.
When to sow in your region
Winter-rainfall Western Cape: Sow in autumn for winter and spring colour in well-drained positions, or again in late winter to spring. Raised beds and pots help in prolonged rain; protect seedlings from snails and slugs. Summer crops need regular water and may pause in extreme heat.
Frost-prone interior: Sow in spring after hard-frost danger. Autumn sowing is suitable only in protected, mild sites because hard frost kills the plants. In very hot areas, aim for flowers before midsummer or sow again as late-summer heat eases.
Humid coast and KZN Midlands: Use the cooler autumn-to-winter window on the coast and prioritise airflow. In the Midlands, sow in early autumn only where winter frost is light, or wait until late winter/spring after hard frost. Avoid wet leaves overnight.
Hot-dry or subtropical interior: Sow in autumn and through the coolest frost-free months, or in late winter before severe heat. Mulch lightly, water deeply and use afternoon shade only during intense heat.
Flower and harvest outcome
Pick flowers when newly open and leaves while young and clean. Harvest only from plants that have not received a pesticide unsuitable for edible crops, wash before use and try a small amount first. The flavour is peppery. Regular picking and deadheading encourage more flowers.
