Sorrel is generous for most of the year, then December arrives and the leaves collapse into something closer to wet paper. That does not mean the plant has given up. Common sorrel and its relatives are perfectly capable of coming through a British winter, and with a little shelter and the right mulch, many will carry on cropping. The trick is knowing what actually damages them. Cold on its own rarely kills a healthy sorrel plant. It is the combination of wet, wind, repeated freezing and thawing, and roots sitting in water that does the harm.

Work Out Which Sorrel You Are Growing

Not all sorrels behave the same way in winter, and the differences matter when you decide how much protection to give.

• Common or garden sorrel (Rumex acetosa) is the toughest of the lot. It usually dies back to a low rosette of small leaves and sits out the worst weather without complaint. In a mild winter it stays semi-evergreen.
• French sorrel (Rumex scutatus), the buckler-leaved kind, is lower growing and more fussy. It copes with cold reasonably well but hates winter wet, and a waterlogged crown can rot before spring.
• Red-veined sorrel (Rumex sanguineus) is hardy enough, but its thinner leaves mark and shred in wind and frost. Expect it to look tired by January and to regrow from the base.
• Sheep's sorrel is small, wiry and thoroughly at home in British conditions. It needs almost nothing from you.

So the priority is drainage and shelter rather than warmth. A plant in free-draining soil against a wall will outlast one in soggy clay in the open, even in the same garden.

Tidy Up Before the Cold Settles In

Late October and November are the months to put the garden to bed, and sorrel rewards a bit of housekeeping. Start by clearing fallen leaves and old plant debris from around the crown. That litter holds moisture against the base of the plant and gives slugs somewhere to spend the winter.

Next, cut away any tatty, mildewed or rust-spotted leaves, taking them right down to the base. Do not cut the whole clump to the ground. Leave the small central rosette intact, because those leaves are still photosynthesising and feeding the roots. If a clump has become dense and congested, early autumn or early spring is the moment to lift it, split it and replant the strongest sections with a decent gap between them.

Mulch Well, but Keep the Crown Clear

A mulch of well-rotted compost or leafmould, spread 3–5cm deep around the plant, insulates the soil and stops the freeze-thaw cycle heaving shallow roots about. Apply it while the ground still holds some warmth rather than after the first hard frost.

The important detail is the crown. Keep mulch a couple of finger-widths away from where the stems emerge. Piling damp material over the growing point is the quickest way to lose a sorrel plant to rot, especially French sorrel. Compost, leafmould and spent mushroom compost all work well. Straw is less useful here; it shelters slugs, and in a wet winter it stays sodden. On heavy clay, fork in some grit or composted bark around the crown first, so water drains away rather than pooling.

Protection for Plants in Open Ground

You do not need a greenhouse. A few inexpensive options will keep leaves coming:

• Cloches — a bell cloche over a single plant, or a tunnel cloche along a row. Ventilate on mild, still days to prevent mould.
• Horticultural fleece — a single layer for light frosts, doubled for a cold snap. Weight the edges down, and lift it during mild spells.
• A cold frame — ideal for two or three plants, and the best choice if you grow French sorrel, because it keeps rain off the crown.
• Shelter — a south-facing wall or a windbreak of netting. Wind does more damage to evergreen leaves than frost does.
• Dry leaves and netting — in exposed, very cold gardens, a loose heap of dry leaves over the crown, held in place with netting, works well. Clear it in early March.

Whatever you use, check it after storms. A cover that has blown loose is worse than none at all.

Looking After Sorrel in Pots

Roots in containers freeze far harder than roots in the ground, so pots need extra thought. Stand them on feet, bricks or pot risers so the drainage holes are not sitting in a puddle. Move them against a house wall or into a sheltered corner where they catch whatever winter sun there is. Wrapping the pot in bubble wrap, hessian or an old blanket insulates the rootball nicely; you can also sink the pot into a spare patch of soil or a heap of compost for the winter.

Water sparingly and only when the compost is drying out. Winter watering is best done in the morning on a mild day, never in the evening with a frost forecast. Terracotta is prone to cracking in hard frost, so a plastic or glazed pot is safer in the coldest spot. Top-dress with fresh compost in late February and repot into a slightly larger container in early spring.

Harvesting Through Winter

Sorrel grown under cover will often crop right through, and even unprotected plants will give you a few leaves in a mild spell. Pick the outer leaves and leave the centre of the rosette to keep growing. Take two or three leaves from each plant rather than stripping one bare.

Expect winter leaves to be smaller, sharper and more acidic than summer ones. They are still excellent shredded into soup, stirred through a sauce for fish, or folded into an omelette at the last moment. Frost-damaged leaves turn grey and mushy; pull those off and bin them rather than leaving them to rot against the crown.

Forcing an early crop

In late January, cover one healthy plant with an upturned bucket or a cloche. In two or three weeks you should have pale, tender leaves at exactly the point when the kitchen has nothing else green. Do not force the same plant two years running — give it a season to recover.

Problems to Watch For

Slugs and snails stay active in all but the hardest weather, so lift pots and check under mulch every week or so. Crown rot is the real killer, and it shows as brown, soft tissue at the base of the plant; improve drainage and pull the mulch back if you see it. Orange-brown pustules on the undersides of leaves are sorrel rust — remove affected leaves and put them in the bin, not the compost heap. Under cover, aphids can appear in late winter; a firm squirt of water usually deals with them.

A Simple Winter Routine

Late October to November: clear debris, cut out tired leaves, mulch around the crown, set cloches or fleece in place. December to February: check plants weekly, ventilate covers on mild days, water pots sparingly, harvest lightly. January to February: force one plant for early leaves. Early March: clear the mulch back, remove covers gradually, fork the surface lightly and water with a balanced feed as new growth appears.

Then stand back. Sorrel is quick to respond once the days lengthen, and a plant brought through winter in good condition will be throwing out leaves for cutting within a few weeks of the first warm spell.

Photo: Karolina / Pexels