RHS Horticultural Advisor Deirdre McShane shares the tricks she uses for forcing rhubarb, so her family can enjoy homegrown rhubarb crumble even earlier in the year
Some rhubarb varieties are bred to start growing especially early in spring. These can be encouraged to crop earlier still by forcing, which restricts light to the crowns. Deirdre McShane, Horticultural Advisor at RHS Hyde Hall in Essex, shares the best varieties to force and how to get pinker, sweeter stems.
Forcing rhubarb involves cutting off their light in January to make the stems ‘think’ they’re still below ground. As a result, they grow more quickly, are more tender and don’t have the normal green colouring. It’s the lack of green that makes the stems taste sweeter, as well as looking pretty.
In my rhubarb patch, I grow ‘Timperley Early’, which produces deliciously sweet pink stems when forced. Other early rhubarb varieties that are suitable for forcing include ‘Early Victoria’ and ‘Early Superb’.
Only healthy plants that have been in the ground for three or more years are strong enough to be forced, as growing without access to light for a couple of extra months is an exhausting process. I find that I need to rest each crown for at least three years before forcing the same crown again, to allow the plant to build up energy reserves. I have quite a large rhubarb patch, so I can move to different sections each year for forcing.
To force rhubarb, you need to cover the whole of the crown. You can use a terracotta forcing pot, which lasts many years. You can also use a tall bucket or bin, or a large, deep pot that will obscure the light and be tall enough to allow space for the stems inside to grow up to at least 30cm (12in) tall. I use an old terracotta forcing pot. The lid has been glued back together numerous times as my children used to like playing with it, but it still does the job.
If my soil is very wet or frozen, I stand on a wooden board placed on the soil to access the crowns, to prevent damaging the soil structure I’ve worked hard to achieve.
If you grow in a cold garden, you can insulate the sides of your forcing pot with heaps of straw or compost, which may allow an earlier harvest, but here in Essex, I find I don’t need to. Pegging down the sides of a plastic pot, or placing a heavy weight on top, should hopefully stop it from being blown away in strong winds.
I try to check on my plants every couple of weeks, as growth may be faster in milder weather. Once the stems have reached 30cm (12in) in height, usually in about eight weeks, I harvest the stems by pulling them right away from the base.
These tender pink stems are much sweeter than unforced stems and need much less sugar when cooking. My family loves rhubarb crumble as a homegrown winter treat, or rhubarb fool for special dinners.
Once I have harvested all the forced stems, I remove the covering to allow light to reach the crown, and I don’t harvest any more stems from that plant that year. I also like to apply a mulch of well-rotted organic matter, such as homemade compost, around the base of the crowns to help feed up the plant after its endeavours to restore strength and vigour.
Now’s the perfect time to start rhubarb forcing before growth begins in earnest, so give it a go this year and you too can look forward to those sweet early crumbles.
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Pick of the crop
Look for the RHS Award of Garden Merit (AGM) when buying vegetable seed or small plants. You can also download the RHS lists of recommended cultivars.
About the author – Deirdre McShane
Deirdre works part-time as a Horticultural Advisor at RHS Garden Hyde Hall in Essex, as well as being a professional gardener for many years. She enjoys growing to feed her family and is pleased to have passed on her love of the outdoors to her two children.
