How to grow peas

Our calendar puts peas in about five weeks before your last spring frost, which is the earliest sowing of any crop on the site. That is not a rounding error. Peas germinate in cold soil, young plants shrug off frost, and the whole crop is built around finishing before summer heat arrives — because heat is what ends a pea plant, not cold.

The old rule was to sow as soon as the ground can be worked, and it holds. If the soil crumbles rather than smearing when you squeeze it, peas can go in.

The failure mode is worth stating precisely, because it is counter-intuitive: peas do not freeze, they rot. Seed sitting in ground that is wet and warm-ish, rather than wet and cold, is what fails. That is why a mild damp spell in March costs more sowings than a hard frost does, and why sowing into a raised, free-draining row matters more than waiting for warmth.

Solomon's version for a dry garden is the same crop from the other end: peas are the one thing he says needs no irrigation at all, because they mature before the summer drought sets in. Sowing early is not just about an early harvest — it is what puts the whole crop inside the wet half of the year.

Every pea climbs. Varieties sold as dwarf or self-supporting climb a bit less, and what they mostly do is lean on each other until a rain flattens the row.

Give them something. Twiggy prunings pushed into the row — pea sticks, the traditional answer — work as well as anything and cost nothing. Netting, wire mesh or strings between posts all work. The 1912 manual suggests three-foot poultry netting, and specifically recommends sowing a double row six inches apart with the trellis between them, which is a genuinely efficient use of one support.

Put the support in at sowing or immediately after. Pushing stakes into a row of established peas tears roots, and a pea that has flopped and been propped up never does as well as one that climbed cleanly from the start.

Height matters more than strength. A tall variety on a three-foot support crops well up to three feet and then sprawls; the plants are light, so the support only needs to hold them up, not hold them down.

Peas fix their own nitrogen through bacteria in root nodules, so a nitrogen-rich bed produces a mass of lush vine and very few pods. The 1912 manual is explicit: fertilizers high in nitrogenous matter should not be applied immediately before planting, as they tend to produce too great a growth of vines at the expense of pods. Ground well manured the previous year is ideal.

What they do want is drainage and a soil that is not acid. Phosphorus and potassium are useful; nitrogen is not.

Because of that nitrogen fixing, peas leave the ground better than they found it — cut the plants off at soil level when they finish rather than pulling them, and the nodules stay behind to break down where the next crop can use them. It costs nothing and it is the reason peas sit at the head of so many traditional rotations.

Depth is one place old and new advice diverge usefully. Our figure is an inch; the 1912 table says two to three. Its explanation is the interesting part — sow in the bottom of a six-inch furrow and cover with only two or three inches, then fill the trench in as the plants grow. That buries the stem progressively and gives a sturdier plant, which is a technique rather than a depth.

The three types are picked at completely different stages, and picking at the wrong one is the commonest disappointment.

Snow peas — the flat-podded, eatable-podded sorts Burr calls sugar peas — are picked when the pod is full size but the peas inside are still barely visible bumps. Wait and the pod turns fibrous.

Snap peas are picked when the pod has filled out and gone round but is still glossy and crisp. Dull and matt means starchy.

Shelling peas are picked when the pods are well filled and still bright green. A pod that has gone pale or waxy has peas in it that have started converting sugar to starch, which is precisely the difference between a garden pea and a supermarket one.

Whichever you grow, pick every day or two. A pea plant's purpose is to make seed, and once a few pods mature fully the plant reads its job as done and stops flowering. Constant picking keeps it going for weeks longer.

Powdery mildew is the usual end of a pea crop — a white bloom on leaves and pods in warm dry spells late in the season. It is largely a signal that the crop is finishing rather than a disaster; keep picking, and sow a later succession further apart with better airflow if you want to push the season on.

Pea aphids build up quickly in warm weather and are the classic sight on a stressed crop. Predators usually catch up; a hard spray of water knocks numbers back in the meantime.

Mice and birds take sown seed and emerging shoots, which is a genuinely common cause of a row that never appeared. If germination is patchy, dig one up before blaming the seed. Netting over the row until plants are a few inches high solves it.

Pea moth, whose larvae are the maggots found in pods later in the season, is worst on midsummer crops. Very early and very late sowings largely dodge its flight period, which is another argument for sowing early.