Marrowfat, Not Mangetout: A Winter Pea-Shoot Crop From a £1 Bag

Pea shoots are one of the few salad crops that will grow on a windowsill in the dead of winter, and they are also one of the most overpriced things in the supermarket chiller. A 60g punnet can set you back £2.50 in January. A 500g bag of dried marrowfat peas costs about £1.20. That gap is why the dried-pea gamble is worth taking — but it is a gamble, and November light is the reason.

Why marrowfat peas, and what to check before you buy

Marrowfat peas are mature dried peas, the same ones that go into mushy peas. They are cheap, widely available, and they germinate. You are not looking for garden-seed quality; you are looking for food-grade whole dried peas with a decent germination rate. A bag from the supermarket is fine. A scoop from a wholefood shop is often better because turnover is higher and the peas are fresher.

Two checks before you commit a tray. First, look for the word 'treated' or a garden-seed label. Garden pea seed can be treated with fungicide and is not for eating as shoots. Food-grade marrowfat is what you want. Second, do a ten-pea test: put ten peas on damp kitchen paper in a lidded tub, keep them at room temperature, and see how many sprout in five days. Eight or more is good. Five or six means sow thicker and accept a patchy tray. Fewer than five, and the bag is old — buy another.

The soak, the tray and the first ten days

Soak the peas in cool water for 12 hours, no longer. Overnight is easiest. Longer soaking softens the peas and makes them more likely to rot, especially in a warm kitchen.

Use a shallow tray with drainage holes, about 25cm by 35cm, or a reused mushroom punnet. Fill it with 3–4cm of multipurpose compost, firm it gently, and scatter the drained peas fairly densely — roughly 60–80g dry weight for a tray that size. You want them almost touching but not piled up. Cover with 1–2cm of compost and water gently.

Keep the tray somewhere warm (18–20°C) until the shoots break the surface, usually four to seven days. A windowsill is fine if it is not freezing; a dark cupboard is not, because the shoots will stretch and pale. Once they are up, move them to the brightest spot you have.

Timeline, realistically:

The first cut comes when the shoots are 10–15cm tall and the tendrils are just starting to curl. Cut 2–3cm above the compost, above a pair of leaves. Do not pull.

Light on a November-to-January sill

This is the part that decides whether the gamble pays. Pea shoots will germinate in low light because the pea itself is the battery, but they need light to green up and to grow sturdy stems. On a south-facing windowsill in November you get maybe four to five hours of weak sun on a good day. That is enough for a crop, but it will be slower and leggier than a March sowing.

North-facing is a waste of peas. East and west are workable but expect 25–35 days to first cut rather than 18. Rotate the tray every couple of days so the shoots lean evenly towards the glass.

If you have a cheap LED bar, use it. Twelve to fourteen hours a day, 15–20cm above the tray, is plenty. Without one, choose the sunniest sill and accept a smaller harvest.

Temperature matters too. A cool room (14–18°C) slows growth slightly but keeps mould down. A warm kitchen speeds things up and increases the risk of damping off and fuzzy grey mould. Do not put the tray on a radiator.

Mould: the failure mode nobody warns you about

Mould is the main reason a tray of pea shoots fails indoors. It appears as white fuzz on the compost surface or grey fur on the stems, usually around day five to ten. Prevention is mostly airflow and restraint.

• Do not soak longer than 12 hours.
• Use a tray with drainage and water from the bottom once the shoots are up.
• Take the lid or cover off as soon as the first shoots appear.
• Do not crowd the peas; a dense mat of wet peas is a mould factory.
• Pick out any peas that have not germinated and have gone soft.
• Clean trays with hot soapy water between crops.

If you see a small patch of white fuzz on the compost, remove it with a spoon and increase airflow. If grey mould is on the stems, bin the tray — do not eat around it.

The second cut: what actually happens

Cut-and-come-again is real, but it is not unlimited. After the first cut, the peas have spent most of their stored energy. A second flush comes from sideshoots lower down, and it is usually thinner and slower. In my experience, roughly half of trays give a worthwhile second cut, and it is about a third of the first harvest.

To give it a chance, cut high enough to leave two lower nodes, water lightly, and keep the tray in the best light. Feed with a weak liquid fertiliser once. If nothing shows after ten days, compost it and start again.

The supermarket comparison, done properly

Let us cost a tray honestly. Peas: about £0.20 of a £1.20 bag. Compost: about £0.30. Electricity for a light, if used: maybe £0.40 over three weeks. Total: under £1 for a first cut of 150–200g, plus a possible 50–80g second cut.

A supermarket punnet of pea shoots is typically 50–80g and costs £1.50–£2.50. So the tray wins on price per gram, but not by the margin you might expect once you count your time. The real advantage is freshness, and the fact that you can cut exactly what you need rather than watch a bag turn to slime in the fridge.

The flavour of marrowfat shoots is slightly starchier and less sweet than mangetout shoots, but still unmistakably pea. Use them raw in sandwiches, wilted into an omelette, or scattered over a bowl of soup.

The verdict

The dried-pea gamble is worth it if you have a sunny sill and a bit of patience. It is not worth it if you are relying on a north-facing kitchen window and hoping for a salad by Christmas. Sow a tray in mid-November, expect the first cut around 10 December, and treat any second cut as a bonus rather than a promise. For the price of a bag of peas, that is a reasonable bet.