Forcing Rhubarb For an Earlier, Tastier Harvest

, written by Benedict Vanheems gb flag

Rhubarb 'Stockbridge Arrow'

It was a trip to my local food store a few years ago that got me onto growing my own rhubarb. I needed a few of the teasingly tart stalks to cook one of my childhood favourites – rhubarb crumble. The mean portion of bagged up stems on offer was, in my opinion, ambitiously priced, so I settled for apple crumble instead. It's not that I'm mean with my money, I just resent paying over the odds for something I know is a doddle to grow! With my twin rhubarb crowns now firmly established I haven't looked back.

There's immense please to be had from snapping free a stalk or two for an impromptu desert. For those who haven't yet had the pleasure, home-grown rhubarb is quite delicious and it's those stems grown in darkness that are the most desirable of all. Growing plants in the dark, often with the addition of a little warmth, is known as 'forcing'. It's a simple way of tricking nature into early growth. And the results are sublime.

Forcing Rhubarb into Early Growth

Rhubarb will naturally break its fat, overwintering buds in early spring, as soon as temperatures are consistently mild. The stems (also known as rhubarb 'sticks') that result can be harvest as soon as they are big enough, from mid spring right up to the middle of summer, when the plants should be left to recharge for the remainder of the growing season. Forced stems, however, can be enjoyed a whole month sooner and even earlier if you lift sections of your rhubarb crown (roots) and bring them under the cover of a greenhouse or other warmer place.

Rhubarb and forcing pot

Forcing rhubarb creates stems that etiolate – botanical speak for growing pale. Plants need light to photosynthesise and produce chlorophyll, which in turn makes foliage green. Exclude every last shard of light and plants cannot photosynthesise. It sounds almost cruel, but your light-excluded plant will then desperately reach out in search of light, producing smooth, pale stems in the process.

For the gardener these stretched stems have far less of the bitterness associated with traditional, non-forced rhubarb. The pale stems need less sugar to balance their tartness, while the taste is all together more delicate. Combined with their tender texture, it makes forced rhubarb a king among early crops.

How to Force Rhubarb

The easiest way to force rhubarb is to do it in situ, without disturbing the crown, while the plants are still dormant in late winter. The object is to cover promising buds so that light is completely obstructed and, ideally, warmth is introduced. I use a large upturned pot for this. The drainage holes of the pot are covered with thick black gaffer tape to prevent the slightest chink of light from reaching the buds. I then bank straw up against the pot to create a snug microclimate within. You can pack the straw directly around the buds inside the pot but I've always shied away from this for fear that the slugs might find the warm, dank atmosphere that results irresistible.

Terracotta rhubarb forcer

You can buy purpose-made terracotta forcing pots. These handsome bell-shaped beasts cost a fair few pennies. You might get lucky scouring salvage yards and antiques centres. If you can find an original Victorian forcer, snap it up – this is the horticultural equivalent of the family silver! Rhubarb forcers come complete with a lid so that you can take a sticky beak every now to check how your stems are coming along.

If you have a greenhouse or relatively warm outbuilding or garage you can dig up a portion of your rhubarb to enjoy an even earlier crop. Pot up pieces of crown, complete with healthy buds, into large pots of compost. Exclude light as above. Keep the roots slightly moist (but never wet!) so that they don't dry out and stop growing. The warmer it is the quicker the stems will reach upwards, with a temperature of around 18-20°C (64-68°F) producing the speediest crop. Your forced rhubarb is ready to pick as soon as the stems touch the top of their pot or forcer.

Maintaining Stock

Forcing rhubarb isn't a natural process. It's a bit like running a marathon: you get to the end faster but it doesn't half take it out of you! Crowns that have been forced should be left to recover the following year or else you risk weakening the plant and making it susceptible to disease. For this reason it's best to have two or more plants on the go so that one can be forced while the other is having a rest.

Don't be in a hurry to bring in rhubarb for forcing. The crowns need a period of chilling to get them in shape before they are ready to break their dormancy. This conditioning ensures plants have had a proper rest period and will result in stronger growth and thicker stems. It's the same reason why apples and other temperate fruits need a certain amount of cold weather to guarantee full fruiting potential.

Rhubarb 'Red Champagne'

Rhubarb Varieties to Grow

Any rhubarb can be forced, but some varieties have been bred especially with forcing in mind. 'Victoria' is one variety that's widely available and a good all-rounder. Deep-red 'Stockbridge Arrow' is very vigorous and has been bred in Yorkshire's 'rhubarb triangle' – rhubarb from this area of England enjoys Protected Designation of Origin status (the same status that means Champagne can only come from the Champagne region of France). Other varieties to seek out are those with 'Early' in the name, such as 'Timperley Early' – a less-than-subtle hint as to its willingness to make an early start to the season!

By Benedict Vanheems.

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Comments

 
"When I set out to establish a vegetable garden at our new property, the lovely rhubarb roots were the first to be set into the freshly turned earth...asparagus was second! I love growing, cooking and eating rhubarb and prepare it in many ways. One to consider: Rhubarb sauce to be served along with a succulent roast of pork or a rich breast of duck. People who "think" they hate rhubarb are quickly converted to singing its praises. Gardenmuse...here in Virginia, USA"
Gardenmuse on Saturday 9 February 2013
"Great article and superbly written, thank you. The rhubarb I grow is a descendant of my Grandfathers which over the last 30 years, since his death, has religiously followed our family from house to house. To think that divisions of the same plant will be eaten through the generations to come is quite mind blowing! A neighbour of mine once put a bottomless black, plastic bin over her rhubarb (without a lid) to protect it from the rabbits and forgot to take it off. The result was the longest stems I have ever seen pushing their huge leaves out through the top. Is this still forcing or can the bin be used every year? When the forced rhubarb is having it's year of rest, can you still pick from it?"
Helen on Sunday 10 February 2013
"Hi Helen. This would be a sort of halfway forcing! The stems would have been much paler if all the light was excluded. I would go for a completely light-proof bin/forcing jar personally, to get those especially tender stems. In rest years I would pick just a few stems per plant to let it properly recover. Pick at the start of the season then stop to allow plants to properly recover - they need to build their rootstock up again."
Benedict Vanheems on Sunday 10 February 2013
"old council wheelie bins upended over your rhubarb make brilliant forcing jars. We are reaping the fruits of its labour now!"
salome2001 on Sunday 2 June 2013
"I am using a chimney flume ( it was free and clean ) 24 inches high and 16 inches square - I made a lid for it and covered over a crown - the rhubarb has grown very pale pink and some white - leaves are very yellowy - the pulp of the rhubarb is very watery - about 18 inches or longer - stalk is very fragile - Can I still eat it ? "
Uncle Raymond on Friday 23 May 2014
"Hi Raymond. It sounds like you have done the right thing. The rhubarb should be pale pink with yellowed leaves, as you describe. The stalks are certainly edible, so eat away, but avoid eating the leaves, which should be added to the compost heap."
Benedict Vanheems on Wednesday 28 May 2014
"Thank You Benedict I have fully removed the lids as last week I saw some browning ( possible burning ) of the leaves - might be like a sauna - it got up to 28 ' C here in Hamilton ( Canada ) but what I did pick and also gaved to some people from our Church it was deemed very tasty - pity I did not reside further north - Thank You again "
Uncle Raymond on Thursday 29 May 2014
"Glad you've had some good pickings Raymond - good stuff!"
Benedict Vanheems on Friday 30 May 2014
"What a great article. I'm going to try this in the spring. Part of my rhubarb patch is a heritage one. It came from my husband's (hubby is 67) great grandfather's farm and we treasure it. It is more on the green side, but tastier than the red. I am really looking forward to forcing one crown to see how it works."
Rita Wing on Monday 15 September 2014
"Dear Rita. I'm delighted to have inspired you! Good luck with your forcing. Let us know how you get on with it."
Benedict Vanheems on Monday 15 September 2014
"I am in Canada and haven't had a garden for 36 years since I left England. I Am now retired and this year I will have one. I always had one in England and grew up learning from old timers and force growing rhubarb was a norm. I was talking to my new neighbor today and he had never heard of this. It is mid April now and I am ready to pick some of mine and his is still dormant. "
Paul on Saturday 18 April 2015
"I also pickled rhubarb too - Not however the forced crown - the forced rhbarb was really sweet - I enjoyed it but was afraid I shocked my plant - so I will wait till next year before I try another crown perhaps I will plant some seeds from another plant that I did let it grow some - I love experimenting with plants and recipes - thanks again "
Raymond on Saturday 18 April 2015
"Hi Paul. How exciting to be creating a new garden - very good luck with it! Enjoy your just-picked rhubarb."
Ben Vanheems on Sunday 19 April 2015
"When should you stop forcing? "
Mike on Monday 20 April 2015
"Hi Mike. You should stop forcing by mid spring certainly - or even late early spring (around end of March in the UK), so as to give the crown enough time to recover."
Ben Vanheems on Sunday 26 April 2015
"The last two springs I have covered my garden w a black plastic ground cloth to start warming the ground. The rhubarb garden is on the south side of my garage. Gets morning sun and by noon is in the shade of a 150 foot oak tree. The Victoria rhubarb plants (taken from my great grandfathers ~1900 garden) never get really big like I have seen in other places but can be picked through July. I suppose the black plastic warming the soil is a form of forcing??"
Len Sackett on Thursday 7 May 2015
"Hi Len. Yes, the black plastic would warm the ground sooner than it otherwise would, so anything growing in it would be encouraged - or forced - into early growth. Very impressed you have rhubarb plants of such pedigree - a living piece of history!"
Ben Vanheems on Tuesday 12 May 2015
"I live in South Florida and I have no problem with sun or warmth....My question is when should I freeze/refrigerate my crowns so I can force/grow my rhubarb outside during my winter months (dec to feb). I am growing them in the A/C under a L.E.D grow lights inside my house.( I know this is crazy) "
Darrin on Thursday 28 May 2015
"My rhubarb, which was originally taken from my grandfathers garden 35 years ago, hasn't been divided in about 15 years. This year it's come through thin and weakly and I want to move it to a new and improved site. Can I do this now or have I got to wait until autumn? I live in South East England. "
Helen on Thursday 28 May 2015
"Hi Darrin. If you're forcing in the winter months then a chilling period in the fall will help - I would say from about October to November inclusive in your case. This will help the plant to accept that one season has finished and a new one is about to start - just like apples or pears would need a period of chilling to signal to the plant that they will need to flower in the spring."
Ben Vanheems on Monday 1 June 2015
"Hi Helen. I would probably wait until autumn now, when the leaves have died back but before the soil is too cold. That said, if you have a really big clump, you could try transplanting some of the pieces to the edge of the clump now, saving some back should this fail. Keep the transplanted sections well watered."
Ben Vanheems on Monday 1 June 2015
"Can you help advise me please? I've tried planting rhubarb twice now. The first crown tottered through the growing season and eventually died in the winter and the second one has faired no better. It has lived a couple of years now and although it tries to grow it is so venomously attacked by slugs that no stem ever gets big enough to eat. I thought I might get over the slug problem by forcing it, but I've tried twice now and both times after a few weeks the stems that have grown have just fallen over and rotted away. What am I doing wrong?"
Chris on Sunday 28 June 2015
"Hi Chris. The first thing to check is that the crowns are planted at the right depth - not too high that they dry out, and not too deep that they struggle and rot. The slug problem is a tricky one - try setting organic slug traps (see this GrowBlog article: http://www.growveg.com/growblogpost.aspx?id=28). You also need to leave enough time for the plant to properly establish before taking any stems. Is the plant receiving enough light? I wouldn't force any plants until they are well established and thriving."
Ben Vanheems on Monday 29 June 2015
"Thanks Ben. You may have a point re the light thing as I've planted it in what I'd describe as a dappled sunlit area. In truth it doesn't get a huge amount of full sunlight, perhaps an hour or so a day. The crown is now in its second year. I can't really recall what depth I planted it at, but I'd imagine the top of the pot it came in from the garden centre was sat about flush with the surrounding soil. I have been trying beer traps these past couple of weeks. I don't want to use pellets as my tiny terraced town garden is predominantly aimed at wildlife. Most of what I grow is planted in pots and tubs. Would that be an option with rhubarb? I'll perhaps give up with this one, as it looks pretty much finished, and try planting another crown next spring. Many thanks for the prompt reply and the advice. It's much appreciated."
Chris on Monday 29 June 2015
"sometimes simple remedies work and are worth trying , do you drink percolated coffee? it is reported that slugs will not travel over coffee grounds so maybe give it a try. in Alberta I do not have a problem with slugs."
Paul on Tuesday 30 June 2015
"Hi Chris. You can grow rhubarb in pots, but to be honest, given its size, you're best growing it in the ground. Good luck with next year - don't give up!"
Ben Vanheems on Tuesday 30 June 2015
"Thanks again for the advice Ben and Paul."
Chris on Tuesday 30 June 2015
"The rhubarb crown that I had forced last year survived - no worries - however I have noticed that the stalk are thinner - I have picked some but only to put on oatmeal or in the freezer - my wife and I bought a house and in moving I have misplaced my pickled rhubarb recipe "
Raymond on Tuesday 4 August 2015
"I have used an old plastic dustbin to cover one rhubarb crown. Is it possible to put hay round the crown, rather than straw? Molly"
MWhitelawolly on Saturday 13 February 2016
"Hi Molly. Yes, hay should work just as well - just make sure it's nice and dry."
Ben Vanheems on Monday 15 February 2016
"I am just getting ready to harvest my first crop which I planted in the greenhouse at Christmas. Am I right in thinking I should replant the crown in the garden?"
Trevor Overton on Tuesday 29 March 2016
"I only have 1 stalk! But my plants are in complete shade. Would they be better in the sunshine? Molly"
Molly on Tuesday 29 March 2016
"Hi Trevor. Yes, once you have forced the crown, they should be planted back in the garden to recover. Do not force them next year - allow them at least a year to recover."
Ben Vanheems on Wednesday 30 March 2016
"Hi Molly. Rhubarb is a very hungry feeder, so make sure the soil isn't starved of nutrients. A good mulch of well-rotted manure or compost will help it along. The plants prefer an open position in sun, so if you can give them this they should thrive. In complete shade (as opposed to part or dappled shade) they will almost certainly struggle."
Ben Vanheems on Wednesday 30 March 2016
"Tasted some rhubarb gin a couple of weeks ago. Delicious. Anyone have a good recipe?"
Helen on Sunday 10 April 2016
"Thanks! The rhubarb bed is getting some sun now, so maybe the plants will start picking up! I've put compost round both of them, and taken the top off the forced one. Thanks for your help. Molly"
Molly Whitelaw on Sunday 10 April 2016
"Hi Helen. I love rhubarb fool. Cook the rhubarb with a little sugar until it collapses and reduces down into a mush. Check for sweetness and add more sugar if necessary. Allow the rhubarb and its juices to cool. Meanwhile whip up some double cream/thick cream until it makes peaks. Fold in a little Greek-style yoghurt, then add the cooled rhubarb and fold this in. Spoon into glasses and refrigerate to stiffen. When you serve them, you can add a sprig of mint for colour, and perhaps a dusting of icing sugar. Enjoy!"
Ben Vanheems on Monday 11 April 2016
"My fo fed rhubarb has a more earthy flavour than I would like. Is this down to the variety or is there something I can do to improve this next time? Nick"
Nick Addy on Friday 21 April 2017
"Hi Nick. This could be due to either the variety (some are more tender and 'sweeter' than others), or the forcing method used. When forcing rhubarb it's important to avoid as much light as possible, so that the stems are growing in the dark. This gives them a much paler colour, with none of the earthiness or potential bitterness. A good rhubarb forcing pot or similar is ideal. Check that it 'seals' properly into the ground at the bottom, and that the lid is a snug fit next time round."
Ben Vanheems on Monday 24 April 2017
"good morning. I have just looked under my dustbin to find my rhubarb are thin and slimy and they cannot hold themselves up. the rhubarb is slowly getting less and less each year,i have put well rotted manure last year and now thinking do i need a new crown could you please help"
terry on Sunday 7 May 2017
"Hi Terry. Your rhubarb could have been under the dustbin for too long, so that the stems have got too weak and begun to perish. I'm not sure where you are, but forcing like you are doing is normally carried out much earlier in the season - around February to March in most of North America and Europe. By April and certainly May the plants should be left to fully recover by growing free. If you force the same crown of rhubarb year after year, it gets very weak. You have to let it recover - i.e. don't force it at all - for at least a year. So one year forced then the next left to grow naturally and build up the rootstock below. It sounds like your plant could be exhausted. It's worth removing the dustbin and leaving it well alone next year - to see if it recovers. If it's very weak, then you may need to plant a new crown."
Ben Vanheems on Monday 8 May 2017
"Thank you Ben"
terry on Monday 8 May 2017
"Thank you for posting this. I’ve just been watching a lovely documentary called Portrait of Garden. It got me to start digging online to determine the merits of growing rhubarb under a bucket. Your article was very helpful and I look forward to practicing the technique with my plants this spring. "
Amanda Kaplon on Monday 17 September 2018
"Thanks Amanda. I hope your forcing goes well and you enjoy a delicious crop."
Ben Vanheems on Monday 17 September 2018

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