Sweet peas - Growing Guide

Sweet peas – Grow Guide

Discover everything you need to know about sowing and growing sweet peas, in this practical guide.

A table displaying which months are best to sow, plant and harvest.
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Sow
Sow

Do not Sow in January

Do not Sow in February

Do Sow in March

Do Sow in April

Do Sow in May

Do not Sow in June

Do not Sow in July

Do not Sow in August

Do not Sow in September

Do Sow in October

Do Sow in November

Do not Sow in December

Plant
Plant

Do not Plant in January

Do not Plant in February

Do not Plant in March

Do Plant in April

Do Plant in May

Do Plant in June

Do not Plant in July

Do not Plant in August

Do not Plant in September

Do not Plant in October

Do not Plant in November

Do not Plant in December

Flowers
Flowers

Plant does not flower in January

Plant does not flower in February

Plant does not flower in March

Plant does not flower in April

Plant does not flower in May

Plant does flower in June

Plant does flower in July

Plant does flower in August

Plant does flower in September

Plant does flower in October

Plant does not flower in November

Plant does not flower in December

Cut back
Cut back

Do not Cut back in January

Do not Cut back in February

Do not Cut back in March

Do not Cut back in April

Do not Cut back in May

Do not Cut back in June

Do not Cut back in July

Do not Cut back in August

Do not Cut back in September

Do Cut back in October

Do Cut back in November

Do not Cut back in December

We all associate sweet peas with bunches of sweetly scented blooms that offer flower after flower in summer. However, the genus offers perennial types as well as the familiar annuals (Lathyrus odoratus) that are grown for picking.

Advertisement

Browse our plant database for over 45 annual sweet pea varieties to grow.

Perennial varieties may be unscented but they are hardy and reliable garden plants.

Picking continuously will encourage more flowers and prevent plants from setting seed.
lathyrus-odoratus-starlight-2

Planting position

Annual sweet peas should be planted in an open, sunny position in a well-drained but moisture-retentive soil.

Perennial types, such as the non-climbing hardy perennial Lathyrus vernus, prefer a position of dappled shade.

Perennial climbers, such as the everlasting sweet pea (Lathyrus latifolius, Lathyrus rotundifolius and L. grandiflorus), require a support to scramble up and a position of sun or light shade. They’re ideal for growing up an old tree stump and they will tolerate very alkaline soils.

The perennial types prefer to be grown in the garden, whereas annuals can be grown in pots if planted in a good compost with a slow-release fertiliser mixed in.

lathyrus-odoratus-lady-turrell-2

Planting technique

Annual sweet peas can be grown from seed or bought as plug plants in spring. Avoid planting them in the garden until the danger of frost has passed. Plant them under a support, such as a wigwam made of bamboo canes. Annual types will grow to about 2m in height. Water in well until they’ve put on good growth. Space them about 20cm apart.

As with the annual types, perennial sweet peas should be planted in a humus-rich soil. Water in well until established.

sowing-sweet-pea-seeds-4

Propagation

Annual sweet peas are easy to grow from seed in either November or spring. A propagator will encourage even germination. If sowing in November ensure you have the room to grow them on in a frost-free place until spring.

To help activate germination nick the seed coat with a knife, avoiding the ‘eye’ area. Either sow seed in 9cm pots (3 to a pot), in root trainers or trays. Sow the seed in a good quality seed compost. Rub out the lumps from the compost. Seeds need to be covered with 0.5cm of compost and watered so it’s damp and not wet. Then place the seed tray or pots in the propagator and keep at about 15°C. If growing without a propagator cover the pots or trays with a sheet of glass until you see signs of germination.

If seeds have been sown in pots or root trainers then they won’t need pricking out. Plants shouldn’t be planted out in the garden until all danger of frost has passed. Before planting harden them off by putting them out in the day and returning them to a frost-free place at night. Seeds can be sown directly into the garden in late April as an alternative. However you grow your sweet peas pinch out the top of seedlings when they reach about 10cm to encourage bushy growth.

Troubleshooting

Young seedlings are prone to slug and snail damage when first planted into the garden. Try beer traps, copper bands, or the biological control, Nemaslug. Find out more about keeping slugs and snails away.

lathyrus-odorata-america-2

Care

Perennial sweet peas require very little care and are simply cut right back in autumn. Annual sweet peas require training up a suitable support and can be grown as cordons – find out more about tying in sweet peas. Picking continuously will encourage more flowers and prevent plants from setting seed. Water annual in very dry weather.

Advertisement

Saving sweet pea seeds

Seed can be collected in early September. Leave the seed pods on the plants until they have turned a paper bag colour. Collect them on a dry day, remove them from their pods and store in paper bags in a dry place until you a ready to sow them. 

lathyrus-odoratus-lipstick-2

Sweet pea varieties to try

  • Lathyrus vernus ‘Alboroseus’ – a hardy perennial bush-forming sweet pea that has tiny pink and white flowers in April. Reaches 35cm in height and spread
  • Lathyrus latifolius ‘White Pearl’ – perennial climber with pure-white flowers from June to late August. Reaches a height of 2m
  • Lathyrus odoratus ‘Matucana’ – hardy annual that is hugely popular and fondly known as the old-fashioned sweet pea. It has scented two-tone purple flowers in summer and is ideal for picking
  • Lathyrys odoratus ‘Lipstick’ (pictured) – a wavy-edged, Spencer type with good scent
  • Lathyrus odoratus ‘Lord Nelson’ – hardy annual grown for picking. Blue flowers with a highly rated scent in summer. Plants reach 2m
  • Lathyrus odoratus ‘Painted Lady’ – hardy annual grown for picking. Bi-coloured blooms of pale and dark pink. Highly scented old-fashioned type. Great for early flowers