When to plant Four-o'clocks in Arid Australia

Arid zone — applies to Alice Springs, Mildura, Broken Hill, Kalgoorlie, Port Augusta and similar areas. Growing elsewhere? Temperate · Cool · Subtropical · Tropical.

Sow four-o'clocks direct from August to November, once all frost has cleared and the soil has warmed, as this plant is frost tender. The dry inland heat actually suits them, and their fleshy tuberous roots make them notably drought-tough once away. Sow the large seed 10–15 mm deep, where it germinates in 14–28 days, and space plants generously at 50–70 cm apart in rows 30–60 cm wide. Fragrant trumpet flowers, which open in the late afternoon, appear in 60–90 days. Around Alice Springs and Kalgoorlie they thrive in full sun and reward evening gardeners with scent as the desert cools.

Sowing calendar — arid zone

Green months are your sowing window: August to November.

Growing notes

Four-o'clocks are one of the best-adapted flowers for arid gardens, so the failures here are mostly about timing and cold rather than heat. Because they are frost tender, sowing too early into a Broken Hill spring can see young seedlings cut down by a late cold snap. Wait until nights have reliably warmed before sowing direct, or start them slightly later in the August–November window if frost has been lingering.

Germination can be slow and uneven at 14–28 days. Soaking the hard seed overnight before sowing 10–15 mm deep speeds and evens the strike considerably.

Once up, they are tough. The plants form fleshy tuberous roots that store water, so established clumps handle heat and dry spells that flatten other flowers. Do not overwater: soggy soil can rot the tubers, which is the main way gardeners lose them. Give free-draining soil, a deep weekly soak in peak summer, and full sun. In the coldest arid pockets the tubers can be lifted and stored over winter like dahlias, or left in the ground under thick mulch where frosts are light. Be aware the seed is toxic if eaten, so site plants away from where children graze.

Four-o'clocks at a glance

Common questions

When can I plant four-o'clocks in Alice Springs?

Sow direct from August to November once frost has passed and the soil is warm, since the plants are frost tender. If cold snaps are lingering, wait for the later end of that window.

Are four-o'clocks drought tolerant?

Very much so once established, thanks to fleshy tuberous roots that store water. New seedlings need regular watering, but mature clumps handle desert heat and dry spells with only a deep weekly soak.

How do I get four-o'clock seeds to germinate faster?

Soak the hard seed overnight before sowing 10–15 mm deep. This speeds and evens what is otherwise a slow, patchy 14–28 day germination.

Do four-o'clocks survive winter in the desert?

In light-frost areas the tubers survive in the ground under thick mulch. Where frosts are hard, lift and store the tubers over winter like dahlias and replant in spring.

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