Five Salad Leaves You Can Grow Through Winter in a Cold Frame

The cold frame sits at the bottom of the garden like a forgotten promise every October, and every year I walk past it for a fortnight before doing anything useful with it. This, I have come to accept, is simply how things go. But the years I have actually followed through, the years I have got seed into that frame by early September, have rewarded me with something quietly remarkable: fresh salad leaves in December, in January, occasionally even into February, picked while the rest of the garden holds its breath under frost.

The idea that the British kitchen garden goes dormant from October to March is one of its most persistent myths. It does slow, certainly. Bare soil appears where beans once climbed, the last courgettes have long been eaten, and the light drops away faster than feels fair. But slow is not the same as finished. With a cold frame and a little forward planning in late summer, you can keep the salad bowl going through the coldest months. The key is choosing varieties that are genuinely suited to low temperatures and low light, not just varieties that claim to be hardy on the packet and then quietly give up by November.

Here are five that will not let you down.

Mizuna

Mizuna is a Japanese mustard green with finely serrated leaves and a mild, slightly peppery flavour that mellows further in cold weather. It is one of the hardiest salad crops you can grow under glass, tolerating temperatures that would reduce most lettuces to cold wet mush. Sow direct into the cold frame in late August or early September, thinning to around fifteen centimetres apart once seedlings are established. It grows quickly in the last of the autumn warmth, producing generous rosettes that can be cut and will regrow reliably two or three times before the plant finally runs out of energy in the depths of winter.

One thing mizuna does not appreciate is sitting in wet compost. If your cold frame sits on clay soil, it is worth working in some grit or sharp sand to improve drainage before you sow. On warmer days in November or December, crack the lid open for an hour or two; the ventilation helps prevent the soft, damp air that invites grey mould to settle over the leaves. This is particularly important for mizuna, which holds moisture in those feathery leaf divisions.

Winter Gem Lettuce

'Winter Gem' is a butterhead-type lettuce bred specifically for cold conditions, and it does what it says with reassuring reliability. It is tighter and more compact than a summer lettuce, forming small, dense hearts that resist the worst of winter temperatures when grown under a cold frame. Sow in late August for a crop that will be ready to harvest from late October onwards. The heads are smaller than their summer counterparts, and you would not serve them at a July dinner party, but for a midwinter salad eaten by lamplight, they are genuinely pleasing.

Space 'Winter Gem' at around twenty centimetres apart. If you sow in modules first and transplant, you gain a little control over spacing, which matters when the frame is small and you are trying to fit in several different crops. Do not expect the leaves to be crisp in the way of a summer cos; winter lettuces are softer, more buttery in texture, and the flavour has a quiet depth that summer varieties rarely achieve.

Corn Salad (Lamb's Lettuce)

Corn salad, also known as lamb's lettuce or by its French name mâche, is possibly the most forgiving winter salad crop in existence. Small, round, dark green leaves with a mild, slightly nutty flavour, it will sit patiently through temperatures that would alarm virtually every other salad plant you care to name. It grows slowly, which requires a degree of patience that not all of us can fully muster by midwinter, but the reward is a genuinely cold-hardy leaf that needs almost no attention.

Sow in late August or September, directly into the frame, scattering the seed thinly and covering lightly. Germination can be slow, occasionally taking two or more weeks, so do not be alarmed if nothing appears for a while. Once established, the plants form neat little rosettes that can be harvested whole or picked leaf by leaf. They are small, which means you need to sow generously to get a worthwhile harvest, but their footprint is modest and they sit companionably alongside other winter salad crops. Corn salad also benefits from good ventilation on mild days; it is less prone to mould than mizuna, but still appreciates moving air.

Land Cress

Land cress is the cold frame's answer to watercress, sharing a similar peppery bite but requiring none of the running water that watercress demands. It is a British native, which perhaps explains why it finds our winters entirely manageable. The leaves are dark and glossy, with a robust flavour that adds welcome punch to a bowl of milder winter leaves, and it remains productive well into January if protected from the very hardest frosts.

Sow in August, thinning to around fifteen centimetres. Unlike some salad crops, land cress can cope with heavier soil without too much complaint, though it dislikes waterlogging as much as anything else grown in a cold frame. Harvest the outer leaves regularly to encourage fresh growth from the centre. The flavour intensifies slightly in cold weather, which makes it a particularly good companion to corn salad or claytonia, both of which are gentle enough in flavour to let the land cress provide the contrast without overwhelming the bowl.

Claytonia (Winter Purslane)

Claytonia, sometimes sold as winter purslane or miner's lettuce, has leaves that are almost impossibly pretty: small, heart-shaped, a clear bright green that looks entirely out of place in a December garden. It is a succulent-textured leaf, mild and slightly mineral in flavour, and it is extraordinarily cold-tolerant, performing reliably through British winters in a cold frame with very little fuss.

Sow from late August through to October, directly into the frame. Claytonia self-seeds prolifically if you allow a few plants to flower in spring, which means that once you have grown it, you may find it appearing of its own accord in subsequent years. This is either a delight or a mild inconvenience, depending on your temperament. The seedlings are small and undemanding, spacing of around ten centimetres is sufficient, and the plants sit quietly through even sharp frosts without damage. Unlike land cress, claytonia has no heat or bite to it, which is partly the point: in a mixed winter salad, it provides volume and tenderness while the cress and mizuna bring the character.

Getting Ventilation Right

The most common mistake with cold frames in winter is not the sowing or the spacing, but the ventilation. On a bright December or January day, the temperature inside a closed cold frame can climb surprisingly quickly, and soft winter salad leaves in warm, stagnant air are an invitation to botrytis. The rule of thumb is simple: if you would open a window in the house, open the cold frame. Even a few centimetres of lift on the lid makes a difference. On genuinely cold nights, close it back down and, if temperatures are forecast to drop sharply below freezing, an old piece of fleece laid directly over the plants inside the frame adds a useful extra layer of protection.

The cold frame does not need to be a sophisticated structure. Mine is a salvaged timber frame with a polycarbonate lid, and it has served reliably for more years than I can accurately count. What matters far more than the material is the orientation: south-facing, sheltered from the worst of the wind, and in a spot that catches whatever winter light is available.

If you have not yet sown for winter salad, the window for getting seed into a cold frame closes in October. An early September sowing gives the best results, allowing plants to establish while there is still enough warmth and light to support meaningful growth. Once the frame is up and running, the work is genuinely minimal: open on mild days, close at night, harvest regularly to encourage fresh growth, and remind yourself, on a cold January afternoon when the rest of the garden looks as though it has given up entirely, that supper might yet include something you grew yourself.