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 enjoyment 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 harvested 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.
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.
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.
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 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.