When to plant Basil in Temperate Australia

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

Basil is sown direct from September to December in temperate Australia, with seed barely covered at 3 mm deep. It is thoroughly frost tender, so there is nothing to gain from rushing — soil that has genuinely warmed in mid-spring produces germination in 7–14 days and seedlings that grow away without sulking. Plants reach picking size 60–90 days from sowing, though you can start pinching leaves well before that. Space plants 25–40 cm apart in a sunny bed, sow a fresh patch every month or so, and you will have soft, fragrant leaves from early summer until the autumn cold shuts things down.

Sowing calendar — temperate zone

Green months are your sowing window: September to December.

Growing notes

As a frost-tender annual, basil lives entirely between the frosts in a temperate climate — sow after the last one in mid-October has safely passed (or slightly earlier in a protected spot), and expect plants to blacken and collapse at the first cold nights of autumn. September sowings only succeed in warm microclimates; for most temperate gardens, October and November sowings are stronger, and a December sowing keeps fresh leaf coming into autumn.

Sow 3 mm deep into fine, moist soil in full sun, and keep the surface damp until germination at 7–14 days. Basil likes richer soil and more water than its Mediterranean reputation suggests — regular moisture keeps leaves soft and sweet, while drought-stressed plants turn tough and bitter. Thin to 25–40 cm each way and start pinching out growing tips once plants have several sets of leaves; every pinch forces the plant to branch and doubles your harvest.

Two failure modes account for most disappointments. The first is sowing into cold, wet spring soil, where seed rots or seedlings damp off. The second is letting plants run to flower in midsummer — once basil bolts, leaf production and flavour fall away fast, so pinch flower spikes the moment they appear.

Basil at a glance

Companion planting

Grows well with

Tomatoes: Repels aphids and tomato hornworm; may improve flavour

Tomatoes: Repels aphids, thrips; may improve tomato yield

Marigold: Together a potent natural pest repellant

Common questions

When can I plant basil outside in temperate Australia?

Sow direct from September to December. Because basil is frost tender, wait until after the last frost in mid-October for open ground — October and November sowings are the most reliable.

How long does basil take to grow from seed?

Seed germinates in 7–14 days in warm soil, and plants reach full harvest size in 60–90 days. You can begin picking individual leaves much earlier once plants are established.

Why is my basil flowering, and should I stop it?

Basil bolts to flower in summer heat, and once it does, leaf flavour and production decline. Pinch off flower spikes as soon as you see them to keep plants producing leaves.

Can basil survive winter in Australia?

Not outdoors in temperate zones — the first frosts around May kill it. Treat it as an annual, or keep a pot on a warm windowsill over winter.

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