RhubarbRheum rhabarbarum

Rhubarb will stay fifteen to twenty years in the same place: choose it with care, outside the vegetable garden rotation, in a corner it can occupy with its leaves a metre across. It likes gentle sun or partial shade, deep soil that stays moist in summer, and hates waterlogged soil in winter, which rots the crown. The foot of a hedge on the east side, the edge of an orchard, the north corner of the vegetable garden or the neighbourhood of the composter suit it. Allow a square metre per plant; two plants are enough for a family fond of tarts.

A month before planting, dig a hole 50 cm each way and set the soil aside. Mix it with an equal volume of well-rotted manure or mature compost, a good barrowload per plant, rhubarb being one of the hungriest plants in the garden. On heavy clay, add a bucket of gravel or coarse sand at the bottom and raise the planting level into a 15 cm mound. On acid soil, a handful of lime or two of wood ash bring the pH closer to the neutrality it prefers. Let the pit settle under the rain before planting.

The simplest and quickest is a piece of crown, taken in March or October from a plant over five years old at a neighbour's, with one or two fat red buds and a fist-sized portion of fleshy root. Garden centres offer potted plants in every season, often the variety Victoria, robust and green-red; for red, sweet stems, look for Frambozen Rood or Holsteiner Blut, and Timperley Early for an early harvest. Sowing, in April-May, gives variable plants to be harvested only in the third year: leave it to the curious.

Plant in March-April, or preferably in October-November, when the soil is still warm and rain is assured. Set the piece in the centre of the pit, buds upwards, so that they sit 2 or 3 cm below the surface, never deeper, otherwise the crown rots. Return the enriched soil, firm by hand, water ten litres, then mulch with 5 cm of compost around the plant without covering the buds. A potted plant goes in at the same depth it had, after teasing out the roots circling at the bottom.

Rhubarb lives reasonably well in a container of at least 60 litres, 50 cm deep and wide, placed in partial shade, in a mix of half potting compost and half garden compost, with careful drainage. It then produces thinner but numerous stems, and makes a fine ornamental plant on a terrace. Watering becomes decisive: every two days in summer, and a dressing of compost or organic fertiliser every spring. Repot or divide every four years in March. In winter, the container stays outside, as rhubarb needs the cold to start well again.

The first mistake is harvesting in the first year, which exhausts a crown that has not yet built its reserves: be patient, and take only two or three stems in the second year. The second is planting too deep or in soil that stays drowned in winter. The third is cutting the stems with a knife, leaving a stump that rots, instead of pulling them with a twist. Finally, putting rhubarb in a vegetable bed, where it gets in the way of crops and is disturbed at every digging, is a classic regret. Set it apart, and feed it without stinting.

In the first year, water copiously in dry weather, ten litres per plant every week from May to September, so that the roots go down deep. After that, an established crown makes do with our rain, except during the increasingly frequent dry spells in July-August: the large leaves wilting in the morning is the signal to give twenty litres at the base. Always water the soil, without wetting the heart. A thirsty rhubarb makes short, fibrous, acid stems and starts to flower; a rhubarb drowned in winter rots beyond remedy.

Rhubarb is fed every autumn: in November, once the foliage has died down, spread a 5 to 10 cm layer of well-rotted manure or compost all around the crown, leaving the heart uncovered. In spring, add a mulch of dried grass clippings or dead leaves that keeps the soil cool and smothers weeds. Nettle liquid diluted to 10 % in April and June supports the growth of the stems. The harvested leaves, toxic to eat but harmless on the ground, go back to the base as a nourishing mulch.

As soon as a flower stem appears, a thick hollow stalk carrying a cluster of buds, cut it at the base with a clean knife: it would draw all the sap at the expense of the stems. A crown that flowers a lot is often old, cramped or underfed. Every eight to ten years, in March or October, dig up the crown with a garden fork and cut it with a spade into pieces each carrying one or two buds and a good portion of root. Replant the outer pieces, the most vigorous, in fresh enriched soil, and compost the woody centre.

Rhubarb has almost no enemies. Crown rot, the only serious disease, comes from drowned soil or compost laid on the heart; plant on a mound in heavy soil and keep the buds clear. Slugs nibble the young shoots in March: evening collection, coarse mulch, and inspection of the forcing bucket. Brown spots on the leaves in a wet summer are harmless, simply remove the affected leaves. Yellowing foliage and a soft crown sometimes signal crown rot; pull up the plant, do not replant in the same spot and start again from a healthy piece elsewhere.

Late January, forcing under a large bucket or an upturned dustbin, surrounded by warm manure, for pink, tender stems from March. March, removal of the bucket after the first forced picking, tidying, nettle liquid. April to Midsummer, harvest, removal of flower stems, watering in drought. July-September, the crown rests, copious watering in a heatwave. October-November, division if needed, thick autumn manuring. December-January, the plant disappears completely below ground; mark its place with a stake so as not to injure it when digging. Never force the same plant two years running.

From mid-April to the end of June, grasp stems over 30 cm long at the base, pull with a twisting movement, and never take more than half the stems at once so the crown can breathe. Stop at Midsummer, 24 June, so the plant can rebuild its reserves. A vigorous crown tolerates a few extra stems in August, but they are more acid and richer in oxalic acid. To bring the season forward, place an opaque bucket in February over a plant more than three years old: in the dark and warmth, the pale, sweet stems can be picked from mid-March.