Forced Rhubarb: What is it and Where Does it Grow?

Reared in pitch black and harvested by candlelight, the growing of forced rhubarb is an astonishing sight. This zingy, candy-pink crop seemingly defies nature by thriving in the dark. Listen closely and you might faintly hear the rhubarb creak as its leafy canopy stretches up towards the roof in the dank, warm cocoon of the forcing shed.

Yorkshire forced rhubarb was given Protected Designation of Origin (PDO) status by the European Commission in 2010. To go by this name, it must be grown in a nine-square-mile area known as the ‘Rhubarb Triangle’, which lies between Bradford, Leeds and Wakefield in West Yorkshire, England. Like white asparagus, it is a winter crop that was traditionally engineered to fill a seasonal gap. It was brought to Yorkshire in 1877 and is now grown by just 12 producers.

Today, forced rhubarb is considered the king of rhubarb by those in the know. Top chefs covet this curious crop for its superior taste, which is not as sharp as summer rhubarb, and its tenderness. Forced rhubarb is also highly desirable because of its bright pink or red skin (the colour depends on the variety), which absorbs into the blanched white flesh during cooking and looks strikingly pretty on the restaurant plate – completely au naturale.

 It sells for around double what you’d pay for regular summer rhubarb, with a growing season running from late January to the end of March. Full of health benefits, it’s packed with potassium, calcium and polyphenols. And even though forced rhubarb grows without any natural light, research has shown that its nutritional content is the same as that of outdoor rhubarb. 

What’s so Special About Yorkshire? 

Yorkshire rhubarb growers claim the Rhubarb Triangle produces the best roots in the world because of the area’s soils and micro-climate. The triangle sits at the foot of the Pennines in a frost pocket that draws plenty of moisture from the waters that cascade down the hills and historically powered the area’s mills. 

Farmers here still enrich their rhubarb soils with shoddy – a wool waste that comes from the sheep who graze in the Pennines, once used in those 19th-century textile mills. 

A Eureka Moment in Farming 

Considering the exacting conditions that are employed to propagate and grow forced rhubarb, it may come as a surprise that its origins were accidental. And despite the fact that it’s synonymous with Yorkshire, the region’s foremost rhubarb farmer claims forced rhubarb was actually discovered in London.

“There’s all different stories about this but the actual true story is it was in Chelsea Physic Garden, where all the ancient herbs and plants are kept,” says Janet Oldroyd-Hulme, whose family has been farming rhubarb in Yorkshire’s Rhubarb Triangle for five generations. 

According to Janet, the discovery was made in 1817 when gardeners were replanting rhubarb roots that had been buried under land drains installed that winter. To their surprise, they noticed delicate pink sticks sprouting from the plants and recognised the potential significance. “Thank goodness it was Chelsea where the horticulturists were, so they didn’t just put their foot on those sticks but were intrigued,” she says.

The discovery of such a nutritional crop that could grow in the cold was a gift in the early 19th century, at a time when there was no refrigeration and seasonal fruit and vegetables were stored through winter. The longer these crops were stored, the more nutrients they lost. Here, they had a product that was growing in winter and was packed full of nutrients – eureka! 

The Science Behind Forced Rhubarb

How can it be possible for a plant to grow without light? In the case of Yorkshire forced rhubarb, the root must sit outside on the Rhubarb Triangle’s moist soil for at least two years after propagation. Left to its own devices rather than harvested, the root hoards energy as it photosynthesises, preparing the rhubarb for a rapid yet brief working life inside the sheds. Just one season in the forcing shed and this fragile plant is as good as dead.

Cloaked in the intense gloom of the forcing sheds, in the depths of winter, frosts kick-start a chemical reaction that awakens the plant and forces it to produce a crop.  

At Janet’s farm, E Oldroyd & Sons, the crops are tended to by candlelight with painstaking regularity. Her farm-hands measure the frost units every morning, then, when they’re just right, they warm the sheds using what is essentially central heating, and gently moisten the plants by misting them. 

The entire growing operation is a lengthy, delicate balancing act: not enough frost and the rhubarb butt won’t produce sticks; too much moisture and the root will rot. Allow any light to enter the sheds and photosynthesis will occur, which causes the rhubarb fibres to thicken and makes the product tougher. Photosynthesis also increases the levels of oxalic acid in rhubarb; the more photosynthesis, the sharper rhubarb tastes. Force the rhubarb too quickly and it loses flavour – farmers in the Rhubarb Triangle take a first harvest only after six to nine weeks. 

Supplying the Stars of Britain’s Restaurant Scene

Janet’s farms supply the three-Michelin-starred restaurants The Fat Duck in Bray and Hélène Darroze at The Connaught in London. Other Michelin-starred restaurants that put forced rhubarb on the menu in winter include Tommy Banks’ The Black Swan at Oldstead in North Yorkshire, while visitors to the farm have included the likes of chefs Raymond Blanc and Rick Stein.

“Chefs are always interested in the forced,” says Janet, who is in the process of erecting more sheds to keep up with increasing demand. But now chefs are experimenting with savoury recipes as well as sweet, eschewing the traditional custard and sugar, and using forced rhubarb to sear through fatty meats and fish like duck and mackerel. 

“And it’s about time,” says Janet, “because this plant is so versatile in cooking – thank goodness the chefs are showing how to get more rhubarb into your body and what lovely recipes you can come up with.”