Dealing with a Glut of Rhubarb

An established rhubarb crownThe base of a perennial plant where roots and shoots meet, often sold and planted as a ready-made dormant plant rather than grown from seed. Full definition → can outproduce any household, and the answer is to pull no more than a third of the stalks at a time, spread the cropping with one forcedCovering plants to exclude light and speed early, tender growth in the dark, most associated with rhubarb and sea kale in late winter. Full definition → crown and an early variety, and freeze or preserve what is left. Stalks are usually picked in spring and early summer, so the glut has a clear start and finish.

For planting and care see the rhubarb growing guide. For forcing in detail see forcing rhubarb in Scotland.

How much you can take

Pull stalks rather than cutting them: pull and twist them off the plant, which stimulates fresh growth. Stalks are ready from spring once they reach 30 to 60cm, depending on the variety. Leave plenty of stems growing. Once the plant is in its third year, take up to a third of the stalks at any one time. Garden Organic is more cautious and leaves at least half the stems growing, so the lower figure is the safer one if you are unsure. Whatever you cannot use, give to neighbours, an allotment society or a plant swap rather than pulling extra.

Stop harvesting in late June or early July, or at most take a few stalks from established clumps after then (RHS), so the crown can rebuild for next year. Make that stop firm: a cool, damp Scottish summer is unlikely to slow the crown for you. If stalks come up thin and weak, the crown is tiring, so stop picking it for the season, mulchA layer of material spread over the soil around plants to suppress weeds, retain moisture, and improve soil structure as it breaks down. Full definition → it, and divide it if it stays weak.

Keeping the crown productive

Mulch each year with well-rotted manure or garden compost, keeping it off the crown itself so the top buds do not rot. Remove flower stems as they appear, which directs energy back into the stalks. Rhubarb dislikes waterlogged soil: on heavy clay or poorly drained ground, grow it in a raised bed or large container. Crown rot is the most common disease and has no remedy, so dig up affected plants and start again on a new site. Divide an overcrowded clump about every five years, in late autumn or winter, to keep it cropping well.

Spreading the harvest: varieties and forcing

More crowns of the same variety on the same soil crop at the same time, so they multiply the glut instead of spreading it. Two things stagger it. First, choose varieties that crop at different times: Timperley Early is one of the earliest and is ideal for forcing, and later-cropping varieties extend the season. Victoria is an old, reliable variety with high yields that can be harvested as baby stems, forced or left to mature. See the best rhubarb varieties for Scotland.

Second, force one strong, established crown. Cover it in mid-winter with a forcing jar, tall bucket or dustbin so the stems grow in the dark. Stalks are ready four to eight weeks after covering, at about 30cm, and they are shorter and sweeter than outdoor stalks. Take them all, remove the cover, and take no more from that plant until the following year (RHS). Forced crowns will not usually produce much of a crop later on, though they can be dividedPropagating a clump-forming perennial by digging it up and splitting it into several smaller pieces, each with roots and shoots attached. Full definition → and replanted in summer, so do not force the same crown two years running. Late frosts can damage young stalks, forced ones especially, so cover new growth with straw or biodegradable fleeceA lightweight, breathable fabric laid or draped over plants to trap a little warmth and keep off frost, wind and some flying pests. Full definition → if a frost is forecast; check the Scottish frost dates for your area. Slugs and snails may damage young shoots, especially under a forcing cover, so lift the cover now and then to look.

Using up the surplus

Rhubarb is best used fresh, but pulled stalks keep in the fridge for a couple of weeks (RHS). Pull only what you will use in the next few days, and freeze the rest.

Rhubarb is usually stewed, baked in pies and crumbles, or used in chutneys and savoury sauces, and it makes cordials and other drinks. Two recipes on this site use up a lot at once: rhubarb and ginger jam and rhubarb chutney.

To freeze it, wash, trim and cut the stalks into lengths to fit the container. Heating the pieces in boiling water for one minute, then cooling them promptly in cold water, helps retain colour and flavour. Pack the pieces tightly, either raw or blanchedExcluding light from part of a growing plant, usually by earthing up, wrapping or covering, so it grows pale, tender and less bitter. Full definition →, into containers without sugar (a dry pack) or covered in cold 40 per cent syrup, leave headspace, seal and freeze. Choose firm, tender, well-coloured stalks with few fibres for freezing.

Leaves and oxalic acid

Eat only the stalks: the leaves are extremely poisonous. They are safe to compost, because the oxalic acid in them breaks down during decomposition. The oxalic acid that builds up in the plant as the season goes on is mostly in the leaves, and the amount in the stems is too little to have a toxic effect.

Common questions

Sources