James Whitaker
Sweet peas are the most generous cut flower a British garden can grow. Sow a few seeds in late winter and, with a bit of pinching and tying in, you will be cutting fragrant bunches from early summer right through to the first frosts. They cost very little, they smell like the whole of summer condensed into a jar, and children adore sowing the fat, wrinkled seeds in cardboard tubes on the kitchen windowsill. Here is how to grow them properly.
Sowing Under Cover
Sweet peas need a long season, so start them early. In most of the UK, sow from late January to mid-March under cover — an unheated greenhouse, a cold frame, or a bright windowsill. If you have a sheltered spot and a cold frame, an autumn sowing in late September or October gives bigger, earlier plants, though mice are more likely to find them over winter.
Use deep containers rather than shallow seed trays, as sweet peas resent root disturbance. Cardboard loo rolls stood upright in a tray, deep root trainers or individual 9cm pots all work well. Fill with a peat-free multipurpose compost, firm it gently and water before sowing.
Sweet pea seed coats are hard. Nicking each one with a nail clipper or the tip of a sharp knife helps water in, and soaking overnight in a saucer of water speeds germination — but sow pre-soaked seeds straight away and do not leave them sitting in water. Push each seed about 2cm deep, one per container.
- Keep at around 15–18°C; too warm and seedlings become pale and leggy.
- Germination takes roughly 7–21 days, depending on variety and temperature.
- Cover trays with a lid or a sheet of glass, and keep them off the floor if mice are about — they will dig out every seed.
Pinching Out the Tips
This is the single step that turns a spindly plant into a cut-flower machine. Once a seedling has two or three pairs of true leaves, pinch out the growing tip just above a leaf pair, using your thumbnails or a clean pair of snips. It feels brutal, but the plant responds by throwing out side shoots from the leaf joints, and every shoot will eventually carry flowers.
After pinching, grow the plants on cool and bright — around 10–12°C is ideal. Good light now prevents the weak, drawn stems that snap in the wind later. Water sparingly and feed only if the leaves begin to look pale.
Planting Out and Supports
Harden plants off over ten days to a fortnight, then plant out from late April in mild areas, or once the risk of hard frost has passed in colder spots. Space them 20–30cm apart. Sweet peas like a deep, fertile, well-drained soil, so dig in plenty of garden compost or well-rotted manure the previous autumn if you can, and add a handful of general-purpose fertiliser at planting time.
They need something to climb. A wigwam of canes, an obelisk, a length of pea netting against a fence or a row of canes with string between them all work. For the longest, straightest stems, try the cordon method:
- Tie the strongest shoot to its support and remove all other side shoots.
- Rub out tendrils and any shoots emerging from the leaf joints.
- Tie in with soft string every 15–20cm as the stem climbs, keeping it vertical.
- If you would rather have a bushy, informal display, simply let the plants scramble and tie in the whole plant loosely.
Watering, Feeding and Cutting
Sweet peas are thirsty. Water thoroughly in dry spells and mulch around the roots with garden compost or bark to hold moisture in. Once the first buds appear, feed every ten to fourteen days with a high-potash tomato feed. Avoid nitrogen-rich feeds, which give you leaves instead of flowers.
Cutting is what keeps them coming. Pick stems every two or three days, ideally in the cool of the morning, taking as long a stem as you can. Cut just above a leaf joint, leaving the plant something to grow on. Most importantly, never let a seed pod develop — the moment a plant sets seed it decides its work is done. Vase life is four to seven days; change the water every couple of days and trim the stem ends.
Pests, Problems and a Few Good Varieties
Slugs and snails will graze young plants, so set traps or barriers at planting time. Aphids gather on soft tips in early summer — a strong jet of water usually deals with them. Powdery mildew appears in dry spells, particularly on stressed plants at the base, so keep watering and remove affected leaves. Pollen beetles in the flowers are harmless and shake out easily.
For scent above all, look for the old-fashioned varieties with the strongest perfume rather than the frilly modern types. 'Matucana' is a deep maroon and purple heirloom with an extraordinary fragrance, 'Mollie Rilstone' is a soft cream with a pink edge, and 'Windsor' and 'April in Paris' are both excellent for cutting. Sow a mix of colours and you will have something for the kitchen table all summer, plus plenty of posies to hand over the garden gate.
