When to plant Aster in Tropical Australia
Tropical zone — applies to Darwin, Cairns, Townsville, Broome, Mackay and similar areas. Growing elsewhere? Temperate · Cool · Subtropical · Arid.
Raise asters from seedlings, sowing into trays in January and again across the dry-season window from July to December. Cover the seed lightly at 5 mm and expect germination in 14-28 days before transplanting out at 20-30 cm spacing in rows the same width apart. Asters need 100-110 days to flower, so a July sowing brings colour through the cooler, drier months that suit them best around Cairns and Townsville. In the tropics these are a dry-season flower, enjoyed for their daisy blooms while the humidity is low, rather than a plant that will hold up through the wet.
Sowing calendar — tropical zone
Green months are your sowing window: July to January.
Growing notes
Asters are half-hardy and prefer cooler, drier air than the tropics usually offer, so the sowing pattern here steers most crops into the dry season. Sow in trays, transplant at 20-30 cm, and you can carry good colour from the July flush through the low-humidity months around Townsville and Mackay.
The classic failure mode is powdery mildew. Asters are notorious for it, and tropical humidity accelerates the problem, coating leaves in white bloom and stunting the plants before they flower well.
- Space at the full 20-30 cm so air circulates freely between plants.
- Water at the base in the morning and keep foliage dry.
- Choose the sunniest, most open bed rather than a sheltered, still corner.
The wet season is the other limit. Warm, saturated soil rots aster crowns, so a January sowing needs very sharp drainage and is best treated as a gamble rather than a reliable crop. For dependable blooms, lean on the July-to-December sowings that flower into the dry. Deadhead spent flowers to prolong the display, feed lightly at budding, and pull plants once they tire rather than nursing mildewed, straggly growth through the returning humidity.
Aster at a glance
| Sowing depth | 5 mm |
|---|---|
| Plant spacing | 20-30 cm |
| Row spacing | 20-30 cm |
| Germination | 14-28 days |
| Days to maturity | 100-110 days |
| Frost tolerance | Half Hardy |
| Method | Plant Seedlings |
Common questions
- Can you grow asters in the tropics?
- Yes, but as a dry-season flower rather than a year-round one. Sow from July to December so plants flower through the cooler, drier months, and expect the wet season and its humidity to end the display.
- Why do my asters get white powdery leaves in Cairns?
- That is powdery mildew, which tropical humidity encourages. Space plants at the full 20-30 cm, water only at the base in the morning, and grow them in an open, sunny position to keep foliage dry.
- When is the best time to plant asters in North Queensland?
- Aim for the dry-season sowings from July onward so the 100-110 day crop flowers while humidity is low. A January sowing is possible but risks crown rot as the wet season peaks.
- How long do asters take to flower from seed?
- About 100-110 days once transplanted. Seed germinates in 14-28 days, so a July sowing gives blooms through the middle of the tropical dry season.
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