How to grow Sweet Pea in New Zealand

Sweet peas are a cottage-garden favourite with ruffled, richly scented flowers in almost every colour, and one of the best cut flowers you can grow. Sow them in autumn or late winter, give them a trellis and lime-sweetened soil, and keep picking to keep them flowering. New Zealand breeder Dr Keith Hammett has bred many varieties for scent and colour. The flowers and seeds are not edible.

📖 Our full guide: How to Grow Sweet Pea in New Zealand

At a glance

Sow

Autumn to late winter in most areas; spring in Central Otago: see the calendar above

Flowers

Spring into early summer

Sun

Full sun, sheltered from strong wind

Soil

Free draining, rich in compost, with lime added

Support

A trellis or teepee up to 2 m for climbing types

Pot

Large pots; dwarf types in baskets

Safety

Not edible; the seeds are toxic

When to sow by region

Region	When to sow	Regional note
Northland	March to June, August and September
Auckland	March to June, August and September
Waikato & Bay of Plenty	March to June, August and September
Central North Island	March to June, August and September
Wellington & Lower North Island	March to June, August and September
Nelson & Marlborough	March to June, August and September
Canterbury	March and April, August and September	Sow Mar to Apr to overwinter as small plants, or Aug to Sep.
Otago & Southland	March and April, September and October	Sow Mar to Apr to overwinter as small plants, or Sep to Oct.
Central Otago	September and October	Sow in spring. Autumn sown seedlings rarely survive the winter here.

Where to plant

Sweet peas need full sun and shelter from strong wind, in free-draining soil rich in organic matter, with lime added to sweeten acid soil. Put up the support before sowing; netting, mesh or a bamboo teepee all work.

Northland to Wellington and Nelson: sow in autumn (March to June) for spring flowers, or in late winter to early spring.
Canterbury: sow in March or April to overwinter as small plants, or in August and September.
Otago and Southland: sow in March or April to overwinter, or in September and October.
Central Otago: sow in spring; autumn-sown seedlings rarely survive the winter.

Choosing a variety

Tall climbing types reach about 2 m and give the longest stems for picking.
Old-fashioned or heirloom types such as Old Spice have smaller flowers but the strongest scent.
Spencer and Mammoth types have large, ruffled flowers on long stems.
Dwarf types need little support and suit pots and hanging baskets.

How to plant

Soak seed overnight in water before sowing to speed germination.
Sow into damp soil about 2 cm deep and 10 to 15 cm apart at the base of the support, and cover lightly.
Do not water for a couple of days after sowing; then water gently only if the soil dries.
Pinch out the growing tip when seedlings have three or four pairs of leaves to encourage bushy plants.
Guide young shoots onto the support.

Watering and feeding

Keep the soil evenly moist once the plants are growing, especially as they start to flower; dry soil shortens the flowering season. Feed every couple of weeks with a liquid fertiliser high in potassium once buds appear.

Pruning and care through the year

Pick flowers often, at least every few days. Plants that are allowed to set seed stop flowering.
Remove any spent flowers and seed pods.
Tie in shoots as they climb.
Protect seedlings from slugs, snails and birds.

Harvesting

Cut stems in the morning when the lowest flowers on the stem are fully open and the top buds are just colouring. Put them straight into water. The more you pick, the more they flower.

Growing in pots

Dwarf sweet peas grow well in pots and hanging baskets; climbing types need a large pot and a frame. Use container mix and keep it evenly moist.

Companion planting

Sweet peas bring bees into the garden in spring.

Good companions

Beans Climbing beans can follow on the same frame once the sweet peas finish.
Lettuce Grows in the light shade at the base of the trellis.

Pests and diseases

Aphids, slugs and powdery mildew are the main problems.

Pests to watch for

Aphids Clusters of insects on shoot tips and flower buds.
Slugs Seedlings eaten off overnight.
Snails Leaves and buds chewed in damp weather.

Diseases to watch for

Powdery mildew White powdery coating on the leaves in late spring, worse in dry soil.
Root rot Plants yellow and collapse in cold, wet soil.

All pests and diseases

Common questions

When should I sow sweet peas in New Zealand?

In autumn or late winter in most areas, for flowers in spring. In Canterbury, Otago and Southland, sow in March or April to overwinter, or in spring. In Central Otago, sow in spring.

Should I soak sweet pea seeds?

Yes. Soaking overnight softens the hard seed coat and speeds germination.

Why have my sweet peas stopped flowering?

They have been allowed to set seed, or the soil is too dry or the weather too hot. Pick the flowers every few days, remove any pods and keep the soil moist.

Are sweet peas edible?

No. Unlike garden peas, sweet pea flowers and seeds are not edible, and the seeds are toxic. Keep them away from children and pets.

Why are my sweet pea leaves white?

That is powdery mildew, common in late spring, especially when plants are dry at the roots. Keep the soil moist, give plants space, and remove the worst leaves.

Sources we checked: Yates NZ: How to grow sweet pea; Kings Plant Barn: Sweet peas grow well guide; Kings Seeds: Sweet pea range.