When to plant Four-o'clocks in Temperate Australia

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

Sow four-o'clocks direct from September to December once all frost has passed, as these are frost-tender plants that will not survive a cold snap. Push the large seed in deep at 10 to 15 mm; it germinates in 14 to 28 days and plants flower within 60 to 90 days, opening their fragrant trumpets in the late afternoon. Give each plant plenty of room, spacing them 50 to 70 cm apart with rows 30 to 60 cm wide, as they grow into substantial bushy clumps. They thrive in the warm summers of Sydney, Perth and Adelaide and reward evening gardeners with scent and colour.

Sowing calendar — temperate zone

Green months are your sowing window: September to December.

Growing notes

Four-o'clocks (Mirabilis jalapa) are grown as a warm-season annual in temperate gardens, though they form fleshy tubers that can be lifted and stored, or left in the ground in milder Sydney and Perth positions to reshoot each spring. They want full sun, free-draining soil and consistent summer watering to keep flowering.

The key failure mode is frost. Because they are frost-tender, sowing before the mid-October frost date exposes seedlings to damage or death, so do not be tempted by an early warm spell. Wait until the soil is reliably warm; the seed sits and rots in cold, wet ground rather than germinating. If your area gets late frosts, start with the tail of the window in November or December.

The second thing to watch is self-seeding and spread. Established plants drop hard, viable seed generously and the tubers persist, so in a warm Adelaide garden they can become a semi-permanent presence. Deadhead if you want to limit this. They are also poisonous if eaten, so site them away from where small children graze. Give them space — crowded plants compete and flower less — and enjoy the late-day scent that gives them their name.

Four-o'clocks at a glance

Common questions

when should I plant four-o'clocks in a temperate garden

Sow direct from September to December, but only after all frost has passed, as they are frost-tender. In cooler pockets wait until November or December when the soil is reliably warm.

why haven't my four-o'clock seeds come up

They can take 14 to 28 days to germinate and need warm soil. Sown too early into cold, wet ground the seed simply rots. They are also large seeds needing 10 to 15 mm depth, so make sure they were sown deep enough.

do four-o'clocks come back every year

In milder temperate positions like coastal Sydney or Perth the tubers often survive winter in the ground and reshoot in spring. Elsewhere lift and store the tubers, or rely on their prolific self-seeding to return them.

are four-o'clock plants poisonous

Yes, the seeds and roots are toxic if eaten. Plant them away from areas where young children play or graze, and take care when handling the tubers.

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