Forcing rhubarb

Published on December 2nd 2018
If you're a fan of rhubarb, waiting for those first juicy stems during these cold, grey days, makes spring feel even further away.
But it's possible to cheat the season and trick the rhubarb into growing early, producing stems from January through until the uncovered plants are ready.
At one point I had 5 rhubarb plant's on my allotment, I quickly realised the error of my ways as I'm the only member of my immediate family who actually likes this vegetable (that's treated as a fruit!).
Crowns were dug and gifted away via the villages recycling page, and I'm now down to 2 plants. These, I take yearly turns to force, and now the leaves have died back, and the winter freeze hasn't yet fully kicked in, it is the perfect time to start.

Outdoor Rhubarb Forcing

Once you've cleared away the old foliage, mulch around the plants with a thick layer of homemade compost or well-rotted manure but not too close to the crown - you don't want it to rot, then cover with a suitable container.
There are many lovely terracotta pots, purposely made and available from garden centres, but if you're on a budget, an upside-down plastic kitchen bin works just as well. If you are looking for tall containers which entirely exclude the light, I use an old leaky water butt and turn it upside-down over the crown, held down against the wind with a sizable stone.
Why exclude light?
Having been fooled into thinking spring is on its way with the slightly warmer conditions inside the upturned pot, the plant will use the energy stored in its roots to grow, looking for the light. As the plant is not using as much energy to produce leaves and photosynthesise, the resulting stems will be soft and tender and brilliant red in colour.
Tip: If you're in a colder part of the country than Wiltshire, you might want to provide additional frost protection to the outside of the pot.
Straw or bubble wrap (re-use last years whenever possible) make great insulating material.
These stems are generally ready to be harvested 8 weeks after you started to force them. Often the first sign that they are ready is either you spot the lid being pushed up or the container lifting slightly. Reach down to the base of the stems and snap off, re-cover and wait for the next ones to grow.
Stop harvesting when unforced rhubarb plants nearby are producing. Remove the container/pot and allow the plant the rest of the year to recover as forcing does weaken the plant.

Forcing Rhubarb Indoors

The Yorkshire Rhubarb Triangle is well known as the home of early rhubarb. There are masses of forcing sheds throughout this 23km² (9 square miles) area between Rothwell, Wakefield and Morley but if you fancy growing some without a purpose-built hothouse, then it's more then possible to do so at home.
  • Pick an established crown over 3 years old. Rhubarb benefits from being split every 3 years to keep it from getting too congested and rather than waste the divisions, this is a perfect way to get an extra crop from the plant. Try to lift it with as much soil attached to the roots as possible.
  • If you don't have a plant ready for division, get to know your local allotment society and keep an eye on recycling pages - there may be surplus plants looking for new homes!
  • Pot it up in garden soil or shop bought compost into a suitable container. This can be anything from large pots to half barrel containers.
  • Leave the pots outside to expose them to a few hard frosts. This tells the plant "yep, winters here" but cover them with a layer of straw or an old plastic compost bag to prevent too much moisture from getting into the pot.
  • Once they've been below 0°C bring them inside to a cellar, garage or potting shed where the temperature can be kept around 10°C.
  • Keep the light excluded with a heavy fabric or a piece of old carpet but check to make sure the plant doesn't dry out.
  • Stems should be ready to pick after 4 to 6 weeks when they reach 30 to 45cm.
Like outdoor forced rhubarb the plant will need to recover after harvesting has stopped. Plant it outside, incorporating plenty of organic matter then leave it for 2 years before taking another harvest. Or if you've enough plants already, add it to the compost heap to help feed those you are keeping.
I'm counting down the weeks to next years rhubarb season already! We made Rhubarb gin for the first time last year, and very yummy it was too!

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