How to Force Rhubarb

I grow a variety of rhubarb called Timperley Early on my allotment, I also have a couple of crowns in my garden. As the name suggests, you get an early crop compared to other rhubarb varieties.

Timperley Early can be ready for picking as early as March, which is one of the reasons why I grow it. Forcing this variety will speed up cropping time even more but I’ve only done this a couple of times, it’s truly early with superb flavour as it is. However, forcing mid to late season rhubarb varieties is well worth doing when there’s little else available from the allotment or garden in early spring.

What does forcing rhubarb actually mean?

Forcing rhubarb means covering the crown to exclude light, forcing it to grow faster for an earlier, sweeter-tasting crop. A tall terracotta pot with a lid called a ‘forcing jar’ is placed over the crown creating a dark and warm environment inside the jar, forcing stems into early and quick growth. You will be able to harvest your rhubarb much sooner than you normally would and it will be much sweeter with a less fibrous texture than usual.

When can I force rhubarb?

Ideally you want to start forcing your rhubarb as soon as you see the short fat buds beginning to swell at the base of the crown, this can be from February onwards depending on variety and weather. Super early varieties such as Timperley Early will already be at this stage towards the end of December through to January if established and healthy.

How to force rhubarb:

1. Remove weeds from the base of the crown and mulch with a thick layer of compost or well rotted manure to give your rhubarb a nutrient boost.

2. Cover the rhubarb crown to exclude light using a traditional forcing jar if you’re lucky enough to own one (they’re rather pricey), a large pot (cover drainage holes), dustbin or water-butt will do the job just as well although they’re prone to blowing over in strong winds, placing bricks on top will help to prevent this.

3. The forced stems will grow quickly, reaching for light they will hit the top of the forcing jar lid within 6-8 weeks. Starved of light the stems will be noticeably different – pale pink with much smaller, bright yellow leaves. Gently pull stems from the base of the crown as you normally would and discard the toxic leaves on the compost heap. The baby pink stems are ready for eating. I remove the forcing jar after a few weeks of cropping to allow the rhubarb to recover naturally, the leaves and stems will return to their normal colour once back in the light.

Only force an established rhubarb crown, meaning it has been growing happily for at least 3 years. A young plant will not have the energy to cope with forcing and may not recover or grow well afterwards. Once you force a crown you should allow it to crop naturally the following year, forcing it year after year could seriously weaken it. Harvest lightly and allow the crown to rest from summer onwards. A good tip is to grow 3 crowns if you have the space, allow one to recover from being forced the previous year, force one and let the other crop naturally, when it should.