Rhubarb

Light and exposure

Rhubarb thrives from full sun to partial shade. In the Herve area, a spot sunny in the morning with a little shade in the afternoon suits it very well and stops the soil from drying too fast in June. It is a large plant, an adult clump easily takes up a square metre, so plan for space.

Avoid only the dark corners and tree roots that would compete with it for water and nutrients. An open spot, at the back of the vegetable garden or along an edge, where you leave it in peace for years, is ideal. Once planted, you do not move it lightly.

Watering

Rhubarb likes the soil to stay cool. It has large leaves that transpire heavily, and a soil that dries out slows stem production. In normal times the Belgian rain is enough, but during the dry spells from May to July, water generously once or twice a week rather than in small dabs.

A good mulch at the base, straw, dried clippings or dead leaves, keeps in the moisture and limits the watering. It is the most useful gesture of the season: it keeps the soil cool while feeding the earth as it breaks down. Take care only not to bury the heart of the plant under the mulch.

Soil and repotting

Rhubarb is very hungry and wants a deep, rich, cool soil. It sends thick roots down deep, so loosen the ground well at planting and bury a good dose of ripe compost or decomposed manure. A poor soil gives thin stems, a rich soil gives thick, generous stalks.

Plant preferably in autumn or at the end of winter, burying the root division so that the bud is left just at the surface, not too deep. Space the plants a good metre apart. Each autumn, bring a good spadeful of compost or manure to the base to sustain this hunger, that is what keeps a plant going ten years and more.

Temperature and humidity

This is a cold-climate plant, perfectly at ease here. Rhubarb is very hardy and stands the winters of the Herve area without flinching, frosts included. The foliage disappears completely in winter, the rootstock stays alive underground and starts again in spring.

Better still, the cold does it good. It needs a period of winter rest in the cold, a vernalisation, to restart with vigour the following spring. Our damp, cool winters are therefore not an obstacle but an asset: it is exactly the climate it needs. There is no point protecting it, it manages on its own.

Pruning and upkeep

Ordinary care comes down to two gestures. First, remove the flower stalks as soon as they rise in spring. Rhubarb tries to flower, a large hollow stem topped with a white plume then points up in the centre: cut it at the base without waiting, because flowering exhausts the plant and drops stem production.

Then, at the end of the season, let the foliage yellow and fade in place in autumn, it returns its reserves to the rootstock. Cut or remove only the completely dead leaves. A good clean-up going into winter, a feed of compost, and the job is done.

Pests and diseases

Good news, rhubarb is one of the healthiest plants in the vegetable garden. It has almost no diseases and no serious pests, which partly explains its reputation as an easy plant. Its robustness means you almost forget it.

The only real risk under our damp climate is crown rot, encouraged by waterlogged soil and a heart buried too deep or drowned under a wet mulch. Plant the bud at the surface and ensure a soil that does not stay wet. Slugs may nibble the very young leaves in spring but rarely attack an established plant. Nothing to worry about in practice.

Propagation

Rhubarb is multiplied by dividing the rootstock, and it is the best way to regenerate it at the same time. Every five to six years, in autumn or at the end of winter when the plant is at rest, dig up the rootstock and slice it into pieces with the spade. Each piece must carry at least one good visible bud and a length of fleshy root. Replant at once, bud at the surface, in well-enriched soil.

This division rejuvenates an old plant that was starting to make thinner stems and gives you new plants for free to set out or give away. Sowing exists but gives irregular, slow plants, best left to the curious: for a vegetable garden, division is faster and more reliable.

Toxicity

Careful, rhubarb is only eaten in part. You consume only the stalks, the fleshy red or green stems. The leaves are toxic: they are rich in oxalic acid and other compounds that cause nausea, vomiting, stomach pain and, in high doses, more serious trouble. This toxicity applies to humans as to animals, dogs, cats and poultry included. Never eat the leaves and do not put them without precaution into compost meant for the vegetable garden, throw them into the general compost.

Month-by-month care calendar

Green Hub tips

• Do not harvest the first year. Let the plant settle in, a little the second year, fully after that: that is what guarantees ten years of production.
• Never eat the leaves, only the stalks. The leaves are toxic, for you as for your animals.
• Harvest by pulling and twisting the stalk at the base rather than by cutting, and always leave at least a third of the stems on the plant.
• Cut the flower stalks as soon as they rise: flowering exhausts the plant and drops the stem harvest.
• Divide the rootstock every five to six years in autumn: it regenerates an old plant and gives you free plants.