How to grow sweet peas and best varieties

The frilly, perfumed blooms of sweet peas, held on long, straight stems, make perfect cut flowers. Plus, the more you pick them, the more buds form to make fresh flowers. They’re easy to grow as well. Most are climbers, which can be trained up teepees of canes, but you can also buy dwarf varieties for pots and baskets.

Which? Gardening magazine grew a range of popular varieties to see which would give us the best display.

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Key facts

Plant type Hardy annual climber 

Position In a sunny border climbing up a fence or obelisk 

Soil Any

How to grow sweet peas: month by month

Best sweet pea varieties

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Full testing results for sweet peas

Sweet peas for scent

Grandiflora sweet peas

Sweet peas for pots

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Types of sweet peas

They’re divided into two groups: grandiflora and Spencer types. For an expert, the distinction is in the ‘keel’ petals (the lowest two petals) – grandiflora types have a ‘clamped’ keel, while Spencer types don’t. For the rest of us the difference is that Spencer types have big, frilly blooms and, despite their name, grandifloras have smaller flowers and stronger scents. 

Modern breeding has blurred these divisions. Nowadays, grandifloras are claimed to have both the big flowers and long stems we look for in cut flowers, as well as the profuse flowering and strong scent we love in the garden.

Sowing

Sow seeds during October or February/March in rootrainers or deep pots using a Best Buy compost for sowing seeds. There's no need to pre-treat seeds. Keep them at 16-18°C and they should germinate in 7-14 days.

Identify your plants with Best Buy plastic-free labels

Mice eat sweet-pea seeds, so cover the seed trays or pots with a propagator lid until they’ve germinated.

Caring for your plants

Overwintering

Once germinated, move them to a cool, sheltered position such as a coldframe. Young sweet peas like growing in cool conditions, but don’t tolerate being frosted. If it’s too warm they can become weak. Cover with fleece during very cold weather.

Try our Best Buy frost-protective covers

Planting

Plant them in March or early April against a support they can wrap their tendrils around, such as a teepee made of bamboo canes, then tie them in initially as they grow.

Help your plants with a recommended soil improver

Picking the flowers

Pick sweet peas regularly to encourage them to keep blooming. At the end of the season, leave some flowers to set seed so you can collect it for sowing in autumn.

Common growing problems

Flower buds falling off

Wet soils, warm days and cold nights can make plants drop their buds. It’s nothing to worry about and they’ll soon recover as the nights warm up.

Virus

Sweet pea plants with virus have several symptoms: leaves become mottled; growth becomes stunted; and flowers are speckled with another colour.

The virus is spread by infected sap. This is usually spread by aphids feeding plant to plant, although it can also be spread on cutting tools so clean them between plants.

Unfortunately once a plant has virus it cannot be cured. The best advice is to remove it before the infected sap can be spread to surrounding plants. Controlling aphids will help to avoid virus problems in the future.

Powdery mildew

In dry summers, powdery mildew can become a problem. Keep plants well watered but don’t wet the leaves. Spraying with a suitable fungicide can slow its spread.

Read more about powdery mildew 

How we test sweet peas

Which? Gardening magazine trialled a number of the different sweet pea varieties at our trial ground in North London. We sowed them in October and grew them in our coldframes through the winter until April, when we planted them outdoors. The varieties for pots were planted in pots and hanging baskets. The ordinary varieties were tied in and deadheaded weekly, and sprayed with insecticide to control aphids and prevent viruses spreading. Throughout summer we noted how strong the scent was, how much flower coverage the plants had and if any were affected by pests or diseases. We also assessed them for the length and thickness of their stems to see if any would be good for cut flowers.