When to plant Sweetpea in Subtropical Australia
Subtropical zone — applies to Brisbane, Gold Coast, Sunshine Coast, Coffs Harbour, Lismore and similar areas. Growing elsewhere? Temperate · Cool · Tropical · Arid.
Sow sweetpeas direct from March to May, planting seed straight where the vines are to climb. Germination takes 7–21 days, and plants flower in around 100 days, so an autumn start brings scented blooms through the mild subtropical winter and into spring. Sow deep at 10–20 mm, spacing seed 5–10 cm apart in rows 30–45 cm apart against a tall support. In Brisbane and Coffs Harbour gardens the trick is getting seed in during autumn, giving the vines the cool, drier run they need before spring humidity arrives.
Sowing calendar — subtropical zone
Green months are your sowing window: March to May.
Growing notes
Sweetpeas are a cool-season climber, and in the subtropics the autumn sowing window is short and important. Sowing March to May lets vines build through winter and flower before the warm, wet spring shuts them down early. Miss the window and you get leaf but few flowers.
The classic problem here is poor germination, usually from sowing into wet soil or old seed. Sow into a free-draining bed, and if seed is hard-coated, a soak overnight before sowing lifts strike rates. Do not overwater once sown, as sweetpea seed rots readily in soggy ground.
Powdery mildew is the second challenge, arriving as the season warms. Grow vines on a tall, open trellis with plenty of airflow, water at the base, and give full sun. Pick flowers often, since regular cutting keeps the vine producing rather than setting seed and stopping. Sweetpeas like a sweeter soil, so a dusting of lime before sowing suits the acidic soils around the Sunshine Coast and Gold Coast. Feed lightly with a low-nitrogen fertiliser as buds form to keep flowers coming without excessive foliage.
Sweetpea at a glance
| Sowing depth | 10-20 mm |
|---|---|
| Plant spacing | 5-10 cm |
| Row spacing | 30-45 cm |
| Germination | 7-21 days |
| Days to maturity | 100 days |
| Frost tolerance | Hardy |
| Method | Sow Direct |
Common questions
- When do I plant sweetpeas in Brisbane?
- Sow from March to May so vines establish over autumn and flower through the cooler winter and early spring. This beats the spring humidity that brings mildew and cuts the season short. Autumn is the only reliable window in the subtropics.
- Why won't my sweetpea seed germinate?
- Wet soil and old or hard-coated seed are the usual reasons. Sow into free-draining ground, avoid overwatering, and soak hard seed overnight before sowing. Fresh seed sown in autumn gives the best strike.
- How deep should sweetpea seed be sown?
- Sow seed 10–20 mm deep, spacing it 5–10 cm apart. Deeper sowing suits these larger seeds and helps anchor the climbing vines. Give them a tall support to scramble up from the start.
- How do I get more flowers from my sweetpeas?
- Pick blooms regularly, which stops the vine setting seed and keeps it flowering. Feed lightly with a low-nitrogen fertiliser as buds form, and grow the vines in full sun on an open trellis. Consistent cutting is the single biggest factor.
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