Forcing Chicory and Rhubarb for Winter Colour

A Little Darkness, a Lot of Reward

By the middle of January, the kitchen garden can feel like a promise nobody kept. Beds are sodden, the last leeks are standing about looking thin, and the seed packets are still weeks away from meaning anything. This is exactly the moment to remember the old glasshouse trick of forcing: lift a few roots in late autumn, pot them up, put them somewhere completely dark, and let them produce tender, pale shoots while everything outside is doing nothing at all.

The science is simple. Denied light, a plant cannot make chlorophyll, so new growth comes through white, soft and sweet rather than green, tough and bitter. Gardeners call it etiolation; the French call the results barbe de capucin and chicons; and anyone who has paid good money for a bag of forced chicory in February knows it is worth the bother. Two crops do this better than any others: witloof chicory for chicons, and rhubarb for those shocking pink sticks that taste of early summer in the depths of winter.

Lifting the Roots After Frost

Timing matters more than technique. Wait until the tops have been knocked back by a proper frost, usually late November into December across most of the UK and a little earlier in the north. That cold spell is not incidental. It tells the root that winter has arrived and primes it to break dormancy once conditions turn warm and dark.

For chicory, lift witloof roots with a fork, starting at the edge of the row so you do not spear the ones you want. Shake off the worst of the soil but do not wash them. Cut the leaves back to about 2–3cm above the crown and trim the taproot to roughly 20cm. Discard any that are forked, split or nibbled by slugs, because they will only rot in the pot.

Rhubarb needs crowns of at least three years old; a young plant forced too soon will sulk for a season afterwards. Leave two or three crowns in the ground unforced so you still have a normal crop in spring. Fork underneath, lift the whole crown, shake off the soil and pull away the dead leaves. If the weather is dry, leave the crowns on the surface for a day so the skin dries a little. A light frost will not hurt them, but do not let a lifted crown freeze solid.

Potting Up in Damp Compost

The compost wants to be moist but never sodden — think of a wrung-out cloth. A decent mix is two parts garden soil or loam, one part leafmould or well-rotted compost, and a good handful of grit or sharp sand to keep it open. Roots sitting in cold, wet compost will rot before they ever sprout.

Chicory roots go into a bucket, an old deep pot or a wooden crate, four or five to a container, with the crowns sitting level with the surface of the compost. Firm them in gently with your knuckles and water them in.

Rhubarb crowns need more room. A large pot or a sturdy box will do, with the roots spread out and the crown just proud of the surface. Do not bury the growing point; that is where the stalks will come from.

The Discipline of Darkness

This is the part people get wrong. The darkness must be total — not dim, not shaded, but black. An upturned bucket or bin over the pot works well; so does a dustbin with the lid on, an upturned terracotta pot with its drainage hole blocked, or a corner of a genuinely dark shed. If any light reaches the shoots, they turn green and bitter and you have wasted six weeks.

Temperature is the other lever. Chicory is happiest at around 10–15°C, rhubarb a touch warmer at 12–16°C. A garage, a cool shed or a greenhouse covered with black polythene is ideal. An airing cupboard is too warm and too dry, and produces stringy, hollow stalks. Check the pots every week and top up the water so the compost stays damp.

• Chicory chicons: ready in four to six weeks, often sooner in a mild spell.
• Forced rhubarb: four to six weeks, with the first sticks sometimes pulling at three.
• Watch for: mould on the surface, which usually means poor air or compost that is too wet.

Cutting and Cooking the Crop

Cut chicory chicons cleanly with a sharp knife, taking a little of the base with them, and a smaller second chicon will often follow from the same root. Rhubarb should be twisted and pulled rather than cut, exactly as you would in summer, so the stub seals itself.

In the kitchen, forced chicory is a different vegetable from the bitter leaves of autumn. Halve the chicons, braise them slowly in butter with a pinch of sugar and a squeeze of lemon, and serve alongside roast pork or ham. They are excellent wrapped in a slice of ham with a spoonful of cream and baked under a lid, or layered in a gratin with cream and a little Gruyère. Raw, the leaves are a fine match for orange segments and toasted walnuts.

Forced rhubarb is delicate enough that it barely needs sugar. Roast the sticks with the zest of an orange and a spoonful of honey, then fold through whipped cream for a fool. A crumble is never wrong, and any excess makes a beautiful cordial or a jar of rhubarb and ginger compote for porridge.

Afterwards, Rest the Roots

Forced roots are spent. Do not try to force the same crown two winters running, and do not expect it to crop well the following spring. Either replant it in a spare corner, water it through dry spells and leave it alone for a year or two, or add it to the compost heap and raise fresh roots from seed or division. Splitting rhubarb crowns every few years keeps them vigorous, and a steady rotation of two or three crowns means you can force one each winter without ever running short.