Forcing is a horticultural technique for tricking plants, which have gone dormant in winter, into thinking it is spring, thus stimulating them to grow out of season, and artificially extending the ‘season’.
There is a supporting video associated with this article. Click here to watch it (opens in a new window) or click the viewer at the end.
Rhubarb has been traditionally forced in Britain for a long time, both at home and on an industrial scale, mainly in West Yorkshire where rhubarb is known as ‘tusky’, a dialect word. I use the word ‘industrial’, rather than agricultural because commercially produced forced rhubarb relied on coal, and on other products of the industrial revolution.
Forcing is a great technique to know as there are very few vegetable growers who don’t have a rhubarb growing somewhere on their plot, and if you ever take over an abandoned allotment or vegetable garden then rhubarb will be one of the survivors, an instant first crop.
There are three ways to force rhubarb:
1 – The traditional garden, or allotment way
2 – Using purpose built, heated, forcing sheds
3 – In a barrel inside an unheated greenhouse or poly tunnel
1 – The traditional garden, or allotment way
The traditional way is to cover a rhubarb crown with a large plant pot, a bucket, a small barrel or, in years gone by, a dolly/peggy tub. This is done early in the year and makes the rhubarb grow a little bit earlier, and provides soft, straight stems. However the rhubarb is still growing in a cold atmosphere, and cold soil, and frosty weather will check its growth. You can lift the covering container later, and allow the rhubarb to continue providing in the usual way.
In the example below a large plastic plant pot (with weight on top) and large plastic bowl are being used.
Traditionally old inverted peggy/dolly tubs were used. These were heavy galvanised tin barrels specifically designed for washing clothes in, (prior to the invention of the washing machine). They were tall, heavy, and light proof, and so perfect for forcing.
A ‘peggy’ or ‘dolly’ tub
Purpose made ceramic forcing pots were once common and can still be obtained now.
In the examples below the first picture was taken in Yorkshire, at a garden centre, and the second in Cornwall, at a pottery.
2 – Forced in purpose built, heated, forcing sheds.
Another way is to dig up the root in winter and take it into a warm dark place. This method was traditionally practiced in huge quantities in forcing sheds, mainly in Yorkshire, where many forcing sheds still remain, most of them derelict sadly. The forcing sheds were used in winter, heated with cheap local coal, to trick the rhubarb into growing, so that people could eat it nearly all year round, such was its popularity.
200 tons of rhubarb used to go to London, by train, from Yorkshire, every week, but the rhubarb industry is much reduced now as rhubarb’s popularity declined during the war years due to sugar rationing. It’s making a slow comeback due to its health properties, and because it’s so easy to grow at home, and also because everyone still likes rhubarb crumble. Below are a couple of pictures of forcing sheds, now abandoned..
The reasons for growing rhubarb commercially in that part of Yorkshire were due to several factors. Firstly it was in the heart of a major coal mining area, the fuel required to heat the forcing sheds. Secondly the many local mills could supply soot, one of the fertilisers. Thirdly many of those mills were woollen mills from which came the other fertiliser ‘shoddy’. Shoddy is a slow release fertiliser, taking three years to fully break down, the lifespan of the growing rhubarb which is earmarked for the forcing sheds. Although modern forcing sheds are now heated by gas the rhubarb fields are still spread with shoddy, a waste product of the woollen industry.
The rhubarb plants are grown in fields for three or four years, long enough for the thick roots to enlarge and store up energy. They are then lifted and stored in the characteristic low roofed, heated, forcing sheds. The warmth triggers growth and the darkness encourages soft straight stems.
My uncle worked in the tusky fields when he was young, doing four hours a night, after school, lifting rhubarb roots and carrying them to the forcing sheds. No need for gyms or pedometers in those days eh?
There are a few people still forcing rhubarb in this way, in the so called ‘Rhubarb Triangle’. Here are a few pictures taken inside a modern commercial forcing shed..
They are amazing places, like walking amongst alien eggs, and newly hatched aliens, or is that just my passion for sci-fi coming through.
The rhubarb grows so fast in these sheds that they make strange sounds, and my dad, when he was a kid, disliked walking past these sheds at night because they made scary noises, so he ran. Imagine that, running away from a vegetable?
3 – Forcing in a barrel, in an unheated greenhouse or poly tunnel
The third method is the one I use every year, in a barrel in the greenhouse. Not artificially heated like the forcing sheds but still much warmer than outside.
If you have a root which needs getting rid of, or big roots which need splitting, then this is a good option for you. Rhubarb usually needs splitting every three or four years. If you have three or four roots you will always have something to split as rhubarb crowns can be divided every three or four years because they get too big. Split one every year, by chopping a large section off an established root, to use it for forcing in your barrel, leaving a good chunk of root in the ground to grow again.
Digging up rhubarb is easier than digging up a tree or shrub because the roots aren’t fibrous, but are brittle and snap easily, making a dull popping sound as you pull on your spade to lever the root up. To see a video on how to dig up a rhubarb root click here, or the link at the end of this article.
When you split an old rhubarb it’s always a problem getting rid of the root because nobody likes to compost a healthy plant. Giving it to a friend or a beginner is the favourite solution, but forcing is another. After all you’ve looked after it for three years, so why not get some benefit from all that energy it has stored. It also makes use of an underused greenhouse or poly tunnel, early in the season.
By forcing rhubarb in the winter you extend the rhubarb season by months giving you fresh, home grown rhubarb for 6 months of the year, or longer.
How to force rhubarb in a barrel
I dig up rhubarb in early winter, put it in a small plastic barrel, and cover it with a piece of cloth. A barrel is good because it is tall and will accommodate the ‘leggy’ stems as they emerge, but you can use any container. If you don’t have a barrel you could put the rhubarb root in a bin liner and put the lot in a cardboard box for darkness, or in a dark cupboard if you haven’t got a greenhouse.
A frosty allotment and greenhouse in the middle of winter
The temperature within the dark barrel is higher than the greenhouse. The cloth keeps in the warmth and humidity whilst allowing excess moisture to dissipate. The cloth also creates the darkness which encourages the stems to grow vertically upwards.
I sprinkle a little water on the roots when they begin to look dry.
Inside the cold greenhouse the rhubarb keeps growing
The barrel goes into an unheated greenhouse and the warmer conditions in there are enough to trigger growth, even in winter. It gives you something to look at, and to get excited about during the slowest months on the allotment. It also gives you a fresh crop to regularly harvest when nothing else is growing. My early varieties of outdoor rhubarb start to show before the indoor root is finished, giving me continuous cropping.
Once the sprouts come you can continually harvest until the root becomes exhausted. You won’t get tons of rhubarb and I get, on average, a small harvest per week using this method. It’s slow at first then runs away as the weather warms up. The amount you get is also dependant on the variety as some rhubarbs force more readily then others.
A small harvest in the middle of winter
Just as important as the harvest is the satisfaction you get from regularly collecting a crop in winter, with very little effort, and with no weeding, and no fuel costs. Once the root is in the barrel then it’s virtually maintenance free.
Rhubarb in a barrel, give it a try next winter!
Videos made in support of this article:
By the way, I force rhubarb in winter mainly so that I can make ‘Tusky Porridge’ whenever I fancy it. The recipe is available on this web site.
Click here to jump to the ‘How To MakeTusky (rhubarb) Porridge’ recipe on this web site