When to plant Nasturtiums in Subtropical Australia

Subtropical zone — applies to Brisbane, Gold Coast, Sunshine Coast, Coffs Harbour, Lismore and similar areas. Growing elsewhere? Temperate · Cool · Tropical · Arid.

Sow nasturtiums direct from February to September, dropping seed 10–15 mm deep straight where they are to grow. In the subtropical belt around Brisbane and the Sunshine Coast the cooler autumn-to-spring stretch suits them best, sidestepping the worst of the summer wet. Seed is large and easy to handle, germinating in 14–21 days once soil has taken up moisture. Thin or space plants 20–40 cm apart, with rows about 30 cm apart, and expect edible leaves and flowers within 70–80 days. They ask for very little: poor soil actually gives you more flowers and fewer leaves.

Sowing calendar — subtropical zone

Green months are your sowing window: February to September.

Growing notes

Nasturtiums are one of the easiest things you can grow around the Gold Coast and Coffs Harbour, but they resent two things: rich soil and standing humidity. Feed them heavily and you get a jungle of leaves with barely a bloom, so skip the fertiliser and let them fend for themselves in ordinary ground.

The real subtropical failure mode is the summer wet. Warm, muggy nights push aphids onto the soft new growth, and the same conditions bring on fungal spotting and collapse. This is why the sowing window here closes off summer: grow them through the drier, milder months instead. If aphids do arrive, hose them off in the morning so foliage dries by evening, or simply leave them — nasturtiums make an excellent trap crop, drawing aphids and cabbage white butterflies away from tomatoes and your brassicas like broccoli, cabbage, cauliflower, kale and Brussels sprouts.

Give them full sun to part shade and let them sprawl, trail over an edge, or scramble up a low support. Deadhead if you want more flowers, and pick leaves and blooms young for peppery salads. They self-seed freely, so one autumn sowing often returns on its own the following year.

Nasturtiums at a glance

Companion planting

Grows well with

Tomatoes: Trap crop for aphids; lures them away from tomatoes

Broccoli: Trap crop for cabbage white butterfly caterpillars

Cabbage: Trap crop lures cabbage white away from brassica

Common questions

When should I plant nasturtiums in Brisbane?

Sow direct any time from February through to September, which covers the milder autumn, winter and early spring. Avoid summer sowings, as the humid wet season invites aphids and fungal rot. Seed goes in 10–15 mm deep and sprouts within 14–21 days.

Why does my nasturtium have lots of leaves but no flowers?

Almost always too much feeding or too-rich soil. Nasturtiums flower best when a little starved, so stop fertilising and let them grow in plain ground. Full sun also lifts flowering compared with a shady spot.

Are nasturtiums good companion plants?

Yes. They work as a trap crop, luring aphids and cabbage white butterflies away from tomatoes and brassicas such as cabbage, broccoli, cauliflower, kale and Brussels sprouts. Plant them near those crops and let the pests gather on the nasturtiums instead.

Can you eat nasturtiums?

Both the leaves and the flowers are edible and have a peppery, watercress-like bite. Pick them young for salads, and use the flowers as a garnish. The green seed pods can also be pickled like capers.

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