When to plant Sunflower in Tropical Australia
Tropical zone — applies to Darwin, Cairns, Townsville, Broome, Mackay and similar areas. Growing elsewhere? Temperate · Cool · Subtropical · Arid.
Sunflowers are the rare crop with no off-season in tropical Australia — sow direct in any month of the year, 8–12 mm deep. Germination takes 6–21 days and blooms follow in 80–100 days, so staggered sowings give flowers year-round in Darwin or Cairns. Spacing sets the outcome: 20 cm apart produces slender stems for cut flowers, while 60 cm apart in rows 60–90 cm apart grows the big single heads with fat seed. The only real timing decision is the wet season — growth is fastest then, but storm winds flatten tall varieties, so stake early or choose dwarf types from November to April.
Sowing calendar — tropical zone
Green months are your sowing window: January to December.
Growing notes
The wet and dry seasons offer two different sunflower crops. Wet-season plants rocket up on free water and heat but face two hazards: monsoon storms that snap or flatten tall stems, and waterlogged beds that rot seed before it sprouts. Sow into mounded soil, favour dwarf or mid-height varieties, and drive stakes in at sowing time — not after the first storm has bent everything over. Dry-season sowings from May to October are slower off the mark and need a deep watering twice a week, but they repay you with sturdier plants and cleaner, longer-lasting blooms.
The most common failure is losing seed in the first week. Birds and rodents dig up freshly sown seed, and in the wet, damping-off can take a whole row of seedlings overnight — net the bed until plants reach 15 cm and always sow a few spares. Full sun is non-negotiable; even light shade produces leaning, small-headed plants.
For seed heads rather than cut flowers, use the wide spacing, feed once when plants are knee-high, then leave them alone — late feeding gives floppy stems. Heads are ready when the backs turn yellow-brown. Cut and hang them somewhere airy, which in Cairns humidity means under a fan or a breezy verandah, or the seed moulds before it dries.
Sunflower at a glance
| Sowing depth | 8-12 mm |
|---|---|
| Plant spacing | 20-60 cm |
| Row spacing | 60-90 cm |
| Germination | 6-21 days |
| Days to maturity | 80-100 days |
| Frost tolerance | Hardy |
| Method | Raise Seedlings,Sow Direct |
Common questions
- Can I plant sunflowers year-round in the tropics?
- Yes — every month of the year is a valid sowing time in the tropical zone. Blooms arrive 80–100 days after sowing, so stagger plantings for continuous flowers.
- Why do my sunflowers fall over in the wet season?
- Monsoon storm winds flatten tall, fast-grown stems. Stake at sowing time, grow dwarf or mid-height varieties from November to April, and avoid heavy late feeding, which makes stems soft.
- How long do sunflowers take to flower?
- About 80–100 days from sowing, after a germination period of 6–21 days. Warm wet-season conditions tend toward the faster end.
- How do I dry sunflower seeds in a humid climate like Cairns?
- Cut heads once their backs turn yellow-brown and hang them in a genuinely airy spot — under a fan or on a breezy verandah. In still, humid air the seed moulds before it dries.
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