How to grow Sweet Pea in Australia
Sweet peas (Lathyrus odoratus) are climbing annuals grown for their ruffled, intensely fragrant flowers in pink, purple, red, white and blue. Sown in autumn in most of Australia, they climb a trellis through winter and flower from late winter into spring, and the more you pick them, the more they flower. They are flowers only: the seeds and pods are poisonous.
📖 Our full guide: How to Grow Sweet Pea in Australia
At a glance
When to sow by region
| Region | When to sow | Regional note |
|---|---|---|
| South East Queensland | March to June | |
| Northern Rivers NSW | March to June | |
| Sydney & Coastal NSW | March to June | |
| Melbourne & Victoria | March to June | |
| Adelaide & SA | March to June | |
| Perth & WA | March to June | |
| Tasmania | March and April, September and October | Sow Sep to Oct, or Mar to Apr in mild coastal gardens for earlier flowers. Cool springs grow superb sweet peas. |
| Canberra & ACT | March and April, September and October | Sow Mar to Apr so seedlings are sturdy before the hard frosts and flower in spring, or Sep to Oct for early summer flowers. |
| North Queensland | April and May | Marginal. Sow Apr to May in the dry for a winter flush. Needs the coolest months NQ can offer. |
| Darwin & Top End | May and June | Marginal. Dry season May to Jun only with the coolest nights. SEQ Mar to Apr sowing lands in the wet. |
Not to be confused with: Peas grown for food. Sweet peas look similar but every part, especially the seeds and pods, is poisonous and must not be eaten.
Where to plant
Sweet peas need at least six hours of sun and deep, fertile, well-drained soil. Dig in compost before sowing, and add a dusting of lime to acid soils, as they like a neutral to slightly alkaline soil. Tall types need a trellis, netting or a teepee about 2 m tall; dwarf types need little or no support.
They thrive in cool weather and are frost hardy, but hard frost can damage the flowers, and heat ends their season. Give them good air flow to reduce mildew.
- South East Queensland, the Northern Rivers, Sydney, Melbourne, Adelaide and Perth: sow from March to June. The traditional St Patrick's Day (17 March) sowing works in cooler areas; in warm areas, April and May sowings are less likely to suffer from heat.
- Hobart and Canberra: sow in March and April so seedlings are sturdy before the hard frosts and flower in spring, or in September and October for early summer flowers.
- North Queensland: marginal. Sow in April and May for a winter flush. Darwin: sow in May and June only, in the coolest part of the dry season.
Choosing a variety
- Old-fashioned or heirloom types have smaller flowers on shorter stems but the strongest fragrance.
- Spencer and other long-stemmed types have large, ruffled flowers on long stems for cutting.
- Dwarf and semi-dwarf types, such as Bijou, need little or no support and suit pots and hanging baskets.
How to plant
- Put up the support before sowing.
- Water the soil the day before sowing so it is damp.
- Sow seed about 1 to 2.5 cm deep and about 15 cm apart along the base of the support, or in small single pots to plant out without disturbing the roots.
- Do not water again for a few days unless the soil dries out. Like food peas, the seed rots in cold, wet soil. Seedlings appear in about 10 to 14 days.
- Give young seedlings a twig or skewer to cling to until they reach the trellis.
Watering and feeding
Once the seedlings are up, water deeply at the base and keep the roots cool with mulch. Avoid wetting the leaves, which encourages mildew.
Start feeding about four weeks after sowing, with a liquid flower fertiliser every one to two weeks. Go easy on nitrogen, which gives leafy growth and fewer flowers.
Pruning and care through the year
- Pinch out the tips of young plants when they have three or four pairs of leaves. This makes them branch and flower more.
- Tie in or weave stems through the support as they climb, especially in windy spots.
- Pick flowers often, every day or two at peak. Remove any spent flowers and pods before they form seed, or the plant stops flowering.
Picking flowers
Cut stems in the cool of the morning, when the top flower bud is just opening and the lower flowers are fully open. Put them straight into water. Sweet peas last about five to seven days in a vase, and the more you pick, the more flowers form.
Growing in pots
Dwarf and semi-dwarf sweet peas grow well in pots and hanging baskets. Use a pot at least 40 to 50 cm wide and 20 cm deep, with a quality potting mix, a small support for semi-dwarf types, and regular watering.
Saving seed
At the end of the season, leave a few pods on your favourite plants until they turn brown and papery. Collect and dry the seeds, label them, and store them in a cool, dry place out of reach of children and pets, as the seeds are poisonous.
Companion planting
Sweet peas bring bees into the vegie patch, but keep them clearly separate from food peas and beans so no one confuses the pods.
Good companions
Pests and diseases
Powdery mildew is the most common problem, especially late in the season. Snails and slugs target young seedlings.
Pests to watch for
- Snails Seedlings chewed off just after they come up.
- Slugs Holes in young leaves and slime trails after rain.
- Aphids Clusters on shoot tips and flower buds.
- Thrips Streaked, distorted flowers and silvery marks on petals in warm weather.
Diseases to watch for
- Powdery mildew White powder on the leaves, worst in spring as the weather warms. Space plants for air flow.
- Downy mildew Distorted seedlings and pale leaves with grey growth underneath in cool, damp weather.
- Root rot Seedlings wilt, yellow and collapse in cold, waterlogged soil.
Common questions
When do you plant sweet peas in Australia?
In autumn in most regions, from March to June. St Patrick's Day, 17 March, is the traditional date in cooler areas; in warmer areas April or May is better. In Hobart and Canberra sow in March and April or in spring. Pick your region at the top of the page for the months.
Are sweet peas edible?
No. Sweet peas are poisonous, especially the seeds and pods. Grow them for their flowers only, keep them separate from food peas and beans, and store saved seed out of reach of children and pets.
Why did my sweet pea seeds not come up?
The most common cause is rot in cold, wet soil. Sow into damp soil and do not water again for a few days. Snails and slugs also eat seedlings as they emerge.
How do I get more flowers on sweet peas?
Pinch out the tips of young plants to make them branch, feed with a flower fertiliser every week or two, and pick the flowers often. Remove pods before they ripen, or the plant stops flowering.
Why are my sweet pea leaves white?
That is powdery mildew, which is common as the weather warms in spring. Space plants well, water at the base, and remove badly affected leaves.
Do sweet peas need a trellis?
Tall types do, about 2 m tall. Dwarf and semi-dwarf types need little or no support and suit pots and baskets.
Sources we checked: Yates: How to grow sweet peas; Gardening Australia: Sweet peas.