When to plant Four-o'clocks in Cool Australia

Cool zone — applies to Hobart, Canberra, Ballarat, Orange, Armidale and similar areas. Growing elsewhere? Temperate · Subtropical · Tropical · Arid.

Sow four-o'clocks direct from September to November, once frost has finished, because this is a frost-tender flower that cold will cut straight down. In cool gardens around Canberra, Orange and Ballarat, wait until the soil has genuinely warmed before sowing the large seed 10–15 mm deep. Germination takes 14–28 days in warm ground, so patience helps. Space plants a generous 50–70 cm apart with rows 30–60 cm apart, as they grow into rounded, shrubby bushes. Flowers, which open in the late afternoon and scent the evening, appear in 60–90 days, giving a solid summer show before the first autumn frost returns.

Sowing calendar — cool zone

Green months are your sowing window: September to November.

Growing notes

The single most important point in a cool zone is frost. Four-o'clocks are frost tender at both ends of the season: a late spring frost kills seedlings, and the first autumn frost blackens the plant. Sow only from September to November once frosts have passed, and site plants in the warmest, most sheltered, sunniest bed you have. In colder pockets around Armidale, starting seed in pots under cover and transplanting after frost buys valuable time.

Give them full sun and free-draining soil; they are drought-hardy once established and flower less in shade. The common failure here is a short, cold season simply not giving the plants long enough to bloom before autumn frost, so anything that speeds them up, warm sowing soil, a sunny wall, cloches early on, is worth doing.

A bonus for cool gardeners: four-o'clocks form a fleshy tuber. Where winters are hard, lift the tuber after the first frost, store it dry and frost-free like a dahlia, and replant in spring for a head start and earlier flowers. Otherwise treat the plant as an annual and resow each spring.

Four-o'clocks at a glance

Common questions

When can I plant four-o'clocks in Canberra?

Sow direct from September to November, only after the last frost has passed, because Canberra frosts kill both seedlings and mature plants. A warm, sheltered spot gives the best results.

Are four-o'clocks frost hardy?

No, they are frost tender at both ends of the season. Late spring frost kills seedlings and the first autumn frost blackens the plant.

Can four-o'clocks survive a cold winter?

The plant itself dies with frost, but it forms a fleshy tuber you can lift and store dry and frost-free like a dahlia. Replant it in spring for earlier flowers.

Why won't my four-o'clocks flower before winter?

The cool-zone season may be too short for the 60–90 day bloom time. Sow into warm soil, use a sunny sheltered wall, and start seed under cover to gain time.

Keep exploring