Available in a wide range of striking colours, from soft pinks and lilacs to vibrant purples and reds, sweet pea flowers are a must for any garden and will flower from May to late September. These elegant annual climbing plants can be full of fragrance and a great in borders, trellises, wigwam frames, wall displays and scrambling over shrubs.
Sweet peas are also a lovely cut flower for vases and displays.
Sweet pea flowers can be grown from seeds or young plants. Annual varieties need replacing each year, but perennial species reappear each season.
When to sow sweet pea seeds
Sow sweet pea seeds in a small pot in October to November, or at the end of January through to April.
How to prepare sweet pea seeds
Sweet pea seeds usually need softening before sowing, because they have a hard coat that disrupts their germination.
Place seeds on a piece of moist kitchen towel or a moist spread of vermiculite (a mineral that helps growth) inside a container in a room that’s warm.
Sow once the seeds have swollen or sprouted.
Some stubborn seeds may not swell. For these, carefully use a sharp knife to take away a tiny chip of the coat, at the end away from the rounded scar ‘eye’, to allow moisture to enter.
How to sow sweet pea seeds
Sowing seeds in a greenhouse, heated poly tunnel or conservatory lets plants start off early in the growing season, before being transplanted outside into your vegetable patch when the soil’s warmer.
- If growing seeds in pots of seed compost first before planting in beds, grow in a cold frame or cold greenhouse first.
- Keep the cold frame lid ajar, unless a heavy frost is coming.
- You can grow two seeds in each small pot and remove the weaker seedling once they germinate.
- Four to five seeds can be grown together in a pot that’s about 5inches (13cm) wide, keeping the seeds 1inch (2.5cm) apart.
- Water the seeds but take care not to overwater.
- With pots that have several seedlings growing, carefully transplant each to a 3inch (8cm) pot when they reach about 2inches (5cm) tall.
- When plants get to 4inches (10cm), pinch (remove) the shoot’s top with your thumb and a finger. Do this just above a healthy-looking leaf and it’ll help side shoots grow.
How to prepare the soil for sweet peas
Young sweet pea plants can go in the ground around April. You can also sow seeds direct into the soil at this time, as the soil has usually warmed up.
Choose a sunny, well-drained soil location with room for the sweet pea to climb or, depending on the variety, develop a bushy growth.
A soil spot that has some wind shelter is a good idea.
About a month before planting, dig good quality compost or manure into the ground and add a fish-based general-purpose fertiliser. Remove any weeds.
How to harden off sweet pea plants
Water plants again immediately before planting out.
- There’s no need to separate young plants that have been sent to you in multi-sown modules. These can be trained separately on the support canes.
- Securely place canes or wigwams in the soil.
- Plant plants about 3inches (7.5cm) away from any cane or support, with 10inches (25cm) between plants.
- Fill in the soil around the plants and water.
- Keep well-watered in hot weather.
How to feed sweet pea plants
Sweet peas are a hungry variety, so give the plants a liquid feed of fertiliser, such as tomato feed, that’s high in potassium to boost flower growth.
How to support sweet pea plants
Use garden twine to gently tie plants around the canes. A couple of plants can be secured to each support.A simple sweet pea ring will keep canes together and form a pretty wigwam of flowers.
How to dead-head sweet peas
Dead-heading means removing any faded, wilted or dead flowers.
Do this regularly through spring and summer with sweet peas, because it allows the stronger flowers to flourish and will improve the overall appearance and health of the plant.