When to plant rhubarb

Rhubarb is a perennial that stays in the same spot for years, so it is planted, not sown. Plant dormant crowns or divided pieces of root in autumn, once the leaves have died down, or in early spring before growth gets going. Bare-root crowns are sold from about November to March. Container-grown plants can go in at almost any time, but spring and autumn are easiest.

Rhubarb needs a cold winter to break into growth in spring, so it is well suited to Central European and UK winters. What it dislikes are late frosts on the young spring shoots, so avoid frost pockets.

Give rhubarb an open, sunny spot; it copes with light shade. It wants deep, fertile soil that holds moisture but never sits wet: the roots reach down about a metre, and the crown rots in waterlogged ground. Rhubarb is a hungry plant (Starkzehrer), so dig in two bucketfuls of well-rotted manure or compost per square metre before planting.

Plant each crown so the buds sit at the surface or just below it, no more than about 0.8 in deep. On heavy or wet soil, keep the crown tip just above the surface. Firm in and water.

Each plant needs about a square metre: 30–39 in in every direction. That means one plant in a 120 × 80 cm raised bed, and only if the bed is deep; rhubarb is happier in open ground.

Buy healthy crowns or take a division from a vigorous, disease-free plant. A good division weighs at least 400 to 500 g and has at least one strong bud.

Each spring, spread a mulch of well-rotted manure or compost about 2.8 in deep around the plant, without covering the crown. On reasonable soil that is all the feeding rhubarb needs. Water in long dry spells, especially in the first year.

Rhubarb sends up tall flower stalks in early summer. Break or cut them off at the base as soon as you see them; flowering takes strength away from the stalks you want to eat.

After about five years, clumps get crowded and the stalks thinner. Lift the plant while it is dormant, split it with a spade into pieces with at least one good bud each, and replant the healthiest pieces in freshly enriched soil.

Patience pays with rhubarb. Don't pick anything in the first year, so the plant can build up its roots. In the second year take only a few stalks; from the third year you can harvest normally.

The season runs from about April or May to late June. Never take more than about a third of the stalks at one time. Hold a stalk near the base and pull it away with a slight twist rather than cutting it: cut stubs can rot.

Stop by the end of June. The traditional end date in German-speaking countries is St John's Day, 24 June. After that the plant needs its leaves to rebuild its reserves for next year, and the stalks get tougher and contain more oxalic acid as the season goes on.

Cut off the leaves straight after picking. They contain a lot of oxalic acid and are poisonous, so never eat them, but they are safe on the compost heap, where the acid breaks down.

For tender, pale pink stalks weeks ahead of the main crop, cover an established plant in mid-winter with a forcing pot, a tall bucket or an upturned bin so the new shoots grow in the dark. They are ready about four to eight weeks later.

Forcing takes a lot out of a plant. Only force strong, established plants, and don't force the same plant two years running. Early varieties such as 'Timperley Early' force best.

Rhubarb is tough, but a few things go wrong. Crown rot is the main one, almost always on wet, badly drained soil; cut out rotten parts promptly, and move the plant if the site stays wet. Slugs and snails eat the young spring shoots, and late frosts can scorch them.

Leaf spot diseases such as Ramularia cause brown spots on the leaves but rarely matter much. Weak, stunted plants with mottled leaves may carry a virus: dig them up and start again with healthy stock.

Rhubarb belongs to the knotweed family with sorrel and buckwheat. It stays put for years, so it doesn't take part in a vegetable rotation. When you divide it, replant into freshly manured ground.