When to plant Nasturtiums in Temperate Australia

Temperate zone — applies to Sydney, Melbourne, Adelaide, Perth, Newcastle and similar areas. Growing elsewhere? Cool · Subtropical · Tropical · Arid.

Sow nasturtiums direct from August to December, and again in January and February for a second flush, dropping seed 10–15 mm deep straight where they are to grow. The large seed germinates in 14–21 days once the soil warms, and plants reach flowering maturity in about 70–80 days. Space them 20–40 cm apart, allowing 30 cm between rows, and choose a lean, free-draining spot in full sun. In temperate gardens around Melbourne and Adelaide they thrive on neglect, so keep the soil poor rather than rich for the best flower-to-leaf ratio.

Sowing calendar — temperate zone

Green months are your sowing window: August to February.

Growing notes

Nasturtiums are one of the easiest flowers to raise in temperate zones, and their scrambling habit suits garden edges, spare beds and pots along a Sydney courtyard wall. Sow after the mid-October frost has cleared for the earliest reliable stand, or take advantage of the mild autumn window in February to establish plants that flower into the cooler months. They ask for very little: full sun, occasional water, and no feeding.

The most common failure here is a lush wall of leaves and almost no flowers. This is nearly always over-rich soil or too much nitrogen. The fix is simple: stop feeding, cut back on water, and let the plant feel slightly stressed, which pushes it into bloom.

Nasturtiums also earn their place as a trap crop. Aphids and cabbage white butterfly will congregate on them in preference to your brassicas and tomatoes, so plant a border near broccoli, kale or cauliflower and let the nasturtiums take the hit. Squash heavy aphid colonies with a hose or your fingers rather than spraying, since the flowers, leaves and green seed pods are all edible and you will want them clean for the kitchen.

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 to plant nasturtiums in Melbourne

Sow direct from August through to December once frost risk has eased, and again in January and February for autumn flowers. In Melbourne the spring sowing gives the longest display. Seed goes in 10–15 mm deep straight into the ground.

why are my nasturtiums all leaves and no flowers

This is almost always soil that is too rich or too much watering. Nasturtiums flower best when slightly stressed, so stop feeding, ease off the water, and give them full sun. Blooms usually follow within a few weeks.

do nasturtiums keep aphids off other plants

Yes, they work as a trap crop. Aphids and cabbage white butterfly prefer nasturtiums to nearby brassicas and tomatoes, so a border planting draws pests away. Remove heavily infested leaves to keep numbers down.

can you eat nasturtium flowers and leaves

All parts are edible, including the peppery flowers, leaves and green seed pods. Pick them young and unsprayed for salads. The pods can be pickled as a caper substitute.

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