Unwins Seeds

How to Grow Sweet Peas from Seed

Sweet peas are a must for any garden. They’re elegant, fragrant, great in borders climbing up trellises or wig-wam frames, disguising an unsightly wall or even scrambling over shrubs in a less-formal display. You can even snip the flowering stems to create a vase of cut-flowers, bringing the outdoors in. They come in a range of colours, to suit all tastes and situations, from dazzling bright reds and whites, to moody pastels.

How to sow Sweet Peas

Sow seeds in a cold frame in early spring or directly in the ground in mid-spring. If growing directly in the ground space at 20cm (8 in) apart.
When sowing, some gardeners soak the seeds overnight to soften the hard coat and trigger the germination process. Some also chip the hard coat slightly which also triggers the germination process.
You can sow two seeds per station and remove the weaker seedling once they germinate.
Label with name of variety and date, once you’ve sown seeds.


Water sweet peas twice a day in the morning and the evening once seedlings have their second pair of leaves. They will be growing fast once the spring months get warmer and will appreciate the twice-daily watering. 

See below, James our horticultural expert showing you our Sweet Pea Growers Kit.

Do not overwater young plug plants

If young seedlings or young plants have rotted, more or often than not it’s down to over-watering.
Prevent this from happening;

• When young, water from above when soil feels dry until roots are emerging from the bottom of the pot.
• Never stand pots in water for a length of time. Roots need to breathe and get sufficient oxygen; if you keep them standing in water they drown.

A good tip for established plants is to stand them in a tray of water overnight, if the soil is dry. In the morning tip out the excess water from the tray. Only ‘flood’ the tray again when soil surface feels dry to the finger tip. Again, make sure you re-visit after a few hours or overnight to tip out excess water.


Sweet Peas are hungry so provide a liquid feed that is high in potassium – this encourages lots of flowering throughout the summer. Just follow the instructions on the pack and give your Sweet peas a boost.


These plants are definitely happiest in a sunny part of the garden. Any south-facing position is ideal, or a sun-soaked wall or back of the border. They’ll be most happy in a well-drained soil that is nutrient-rich. Additional feeding with provide them with the nutrients they need to produce an abundance of flowers.

Other after-care

As your sweet –peas are happily flowering in summer, be sure to remove flowers of those that have been pollinated and have now withered. Remove these flowers means the plant will put its energy into producing more flowers for you to enjoy throughout the summer season.

How to prune

Sweet peas are half-hardy annuals so they put out their abundance of flowers in one season. They may flower, albeit more slowly and sporadically in autumn, until the first frosts of winter, when it will be time to remove them and prepare the soil for next year’s plants.

Flowering period - May- September

Best Varieties
Romeo and Juliet
Percy Thrower

Pests and Diseases - Slugs and snails, Aphids, Fusarium wilt, Mildew



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