Sweet Peas, Sown in Autumn

Nothing in a summer garden smells like a jug of sweet peas on a kitchen table, and nothing rewards a little autumn effort so plainly. Plants sown in October come into flower two to three weeks before a spring sowing, on longer stems, and keep going later.

Sowing, in October

Sweet pea seed has a hard coat. Soak it in tepid water overnight — swollen seeds are ready, and any that stay hard and small can be nicked lightly with the point of a knife on the side opposite the eye, then soaked again.

Sow into deep containers: root trainers, or 9cm pots, or a cardboard toilet roll stood in a tray. Sweet peas make long tap roots and hate a shallow pot. One seed per cell, 2cm deep, in peat-free multipurpose compost.

Water once, then keep only just moist. Sitting wet through a cold November rots more seed than frost ever will.

Overwintering

Put the pots in a cold frame, an unheated greenhouse, or against a sheltered north wall. Cold is not the enemy — warmth is. Sweet peas are hardy to about -5°C as young plants, and a cold winter produces tough, stocky growth. A heated conservatory produces pale, drawn plants that never recover.

Protect from mice, which will take the lot in one night. A sheet of chicken wire over the frame is enough.

When each plant has three or four pairs of leaves, pinch out the growing tip above the second pair. The plant sulks for a fortnight and then throws out four strong side shoots. Do not skip this.

Preparing the ground

Sweet peas are hungry and thirsty. In late winter, dig a trench a spade deep where they will grow and fill the bottom with well-rotted manure or garden compost, then backfill. This is the traditional method for a reason: the reservoir of moisture at depth is what keeps stems long in July.

Choose full sun, with shelter from strong wind.

Planting out and support

Plant out in March or early April, after a week of hardening off. Space 20–23cm apart at the foot of the support, and water in well.

Support must be in place first and must be strong — a mature row of sweet peas in wind carries the load of a small sail:

• Hazel or bamboo wigwam: simplest, and beautiful.
• A-frame with netting: best for a cutting row, easiest to pick from.
• Individual canes, cordon-grown: for exhibition stems, one stem per plant, all side shoots and tendrils removed weekly and the stem tied in. Extraordinary flowers, considerable work.

For the first few weeks, tie the plants in loosely; they will find their own way once the tendrils reach the netting.

Feeding, watering, and picking

Water deeply twice a week in dry spells — a good soak at the roots, not a daily sprinkle. Mulch after planting to hold that water in.

Feed fortnightly from the first buds with a high-potash tomato feed. Nitrogen at this stage gives you a wall of leaves and no scent.

Then the important part: pick constantly. A single pod allowed to set seed tells the plant its work is done, and flowering slows within days. Cut every stem when the bottom two or three florets are open, and go over the row twice a week for pods you missed. A well-picked row flowers for ten weeks; a neglected one for three.

Two problems, honestly

• Bud drop — buds yellow and fall before opening. Almost always a sudden cold snap or erratic watering. It passes.
• Powdery mildew in late summer — inevitable in a dry August. Mulch, water at the roots rather than the leaves, and space plants for airflow. When it takes hold, take the crop you have and cut the row down.

Sow again in March as insurance. But it is the October sowing that gives you the vase you remember.