When to plant Sunflower in Subtropical Australia
Subtropical zone — applies to Brisbane, Gold Coast, Sunshine Coast, Coffs Harbour, Lismore and similar areas. Growing elsewhere? Temperate · Cool · Tropical · Arid.
Sunflowers are easy and sun-hungry, and in the subtropics you can sow the seed direct across a long warm-season window — January to April and August through December. They revel in the heat that troubles fussier plants, so Sunshine Coast and Brisbane gardeners get months of planting opportunity. Push seed 8 to 12mm into warm soil where it will grow, as sunflowers dislike being transplanted, and expect germination in 6 to 21 days. From there it is a fast run of 80 to 100 days to full bloom. Spacing is flexible: pack them at 20cm for smaller cutting stems or give large-headed types up to 60cm.
Sowing calendar — subtropical zone
Green months are your sowing window: August to April.
Growing notes
Sunflowers handle the subtropical summer with ease, but the wet season brings its own hazards. Full sun is non-negotiable, and the plants want deep, free-draining soil — waterlogged ground during a December storm run rots the roots and topples plants. Sow direct at intervals through the warm months for a succession of blooms rather than one glut, spacing at 20 to 60cm depending on the variety and 60 to 90cm between rows.
The tall varieties are the classic casualty of summer storms; a laden head on a two-metre stem is easily snapped by a Gold Coast southerly, so stake early or plant a lower, branching type in exposed positions. Humidity encourages rust and powdery mildew on the leaves, appearing as orange pustules or grey film — space plants generously for airflow and water the roots, not the foliage, to keep it in check.
Birds and rats will strip ripening seed heads, so if you are growing for seed rather than cut flowers, bag the heads with mesh or a paper sleeve as the petals fade. Young seedlings are also a favourite of snails and slugs after rain, which can clear a fresh sowing overnight, so protect them in the first fortnight. Harvest cutting stems as the first ray petals lift, before the pollen sheds.
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
- When should I sow sunflowers in the subtropics?
- Sow direct through the warm season, from August to April, avoiding only the coldest weeks. Successive sowings a few weeks apart give continuous blooms.
- How long do sunflowers take to flower?
- Around 80 to 100 days from sowing to full bloom. Seed germinates in 6 to 21 days in warm soil.
- How do I stop my sunflowers snapping in storms?
- Tall varieties are vulnerable to summer storm winds, so stake them early or grow shorter branching types in exposed spots. Deep, free-draining soil also helps anchor the roots.
- Why are the leaves developing orange or grey patches?
- That is rust or powdery mildew, both driven by humidity. Space plants for good airflow and water at the base rather than over the leaves.
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