When to plant Sweetpea in Temperate Australia

Temperate zone — applies to Sydney, Melbourne, Adelaide, Perth, Newcastle and similar areas. Growing elsewhere? Cool · Subtropical · Tropical · Arid.

Sow sweet peas direct from January to May, setting seed 10–20 mm deep where the plants are to climb. They germinate in 7–21 days and take around 100 days to flower, so an autumn sowing brings the classic perfumed blooms through late winter and spring. Space seeds 5–10 cm apart along rows 30–45 cm apart, with a trellis, tepee or fence in place from the start. Sweet peas are hardy and love a cool run, making the mild autumns and winters of temperate gardens in Melbourne, Adelaide and Perth their natural home.

Sowing calendar — temperate zone

Green months are your sowing window: January to May.

Growing notes

Sweet peas reward cool, steady growing conditions, which is why the January to May window works so well in temperate zones; the vines establish over autumn and flower as the days lengthen in late winter and spring. Sowing later, into warm soil, tends to give leggy plants that bolt into bloom briefly and then fade in the heat.

Give them a deep, rich, well-drained bed and something to climb from day one. The vines cling with tendrils, so netting, a tepee of stakes, or wire against a fence all work along the 30–45 cm-spaced rows. Full sun with cool roots is ideal; a mulch keeps the soil temperature even.

The most common failure is poor or patchy germination. Sweet pea seed has a hard coat, and in cold Adelaide or Ballarat-fringe soils it can sit and rot. Nicking the seed coat lightly or soaking overnight before sowing lifts strike rates markedly. Once flowering starts, pick regularly and deadhead; the moment plants are allowed to set seed pods they stop producing new flowers. Watch for powdery mildew late in the season and keep water at the base rather than over the leaves. A weekly potash-rich feed once buds appear improves both flower size and scent.

Sweetpea at a glance

Common questions

When should I sow sweet peas in Adelaide?

Sow direct from January to May. This autumn window lets the vines establish over the cool months and flower through late winter and spring, which suits Adelaide's mild temperate climate and gives the best perfume.

Why won't my sweet pea seeds germinate?

The hard seed coat is usually the problem, especially in cold, wet soil where seed can rot before sprouting. Nick the coat lightly with a knife or soak the seed overnight before sowing to improve and speed up germination.

How do I keep sweet peas flowering longer?

Pick and deadhead constantly. As soon as plants are allowed to set seed pods they stop making new flowers, so cutting blooms for the vase actually keeps them producing. A potash-rich feed when buds appear helps too.

Do sweet peas need support?

Yes. They are climbers that cling with tendrils, so put a trellis, tepee or netting in place at sowing. Growing them along rows 30–45 cm apart with support keeps the vines healthy and easy to pick.

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