Global warming is threatening crops of Yorkshire’s forced rhubarb.
Growers in the rhubarb triangle, formed by Wakefield, Rothwell and Morley, produce 1,000 tonnes of the protected status delicacy each year.
But Janet Hulme-Oldroyd, who grows forced rhubarb at Oldroyd’s Farm in Carlton, says growing conditions are changing due to climate change and that is affecting yields.
She said: “Early varieties are effected by global warming more than any other as they grow in lower temperatures.”
“Last year yields on early varieties were down 25 per cent.
“This year it looks like being between 25-35 per cent. I blame the poor season on unfavourable growing conditions whilst the root lived outside.”
Forced rhubarb begins life as cuttings taken from a rhubarb plant’s mature crown, two years before harvesting.
When strong enough the cuttings are planted in fields to mature, ready for the forcing sheds. In the sheds the plants grow in the warmth and stored carbohydrates in their roots transform into glucose which gives forced rhubarb its bittersweet flavour.
But this process is only successful if the plant is subject to the right conditions outside.
Mrs Hulme-Oldroyd, whose great-grandfather started the family business in the 1930s, said: “A root must live outside for two to three summers and grow into a large structure full of energy but we’ve had wet summers and droughts - the lot.
“Long growing periods from early Spring to the warmest Autumn on record for a plant that needs long periods of dormancy do not allow the plant to make large energy reserves from which the plant will grow when it is taken into the sheds.
“Not enough stored energy results in lower yields in the warm sheds when we trick them into growth.”
She also said the absence of frost this year was a problem.
She said: “Frost is necessary for the forcing process to start. At this time of year we like all the sheds to be full of roots from early to main crop. This year we have only had enough cold to take in the earliest variety.
“Staff will, after today when we close the last shed of early variety, be on holiday until the new year. Over the holidays we are hoping for nice sunny bright cloud free days and clear frosty nights - traditional English winter weather - so we can get back on track to provide continuity of crop until the outdoor crop is ready for harvest.”
Growers in this part of the world are trying to engineer solutions to adapt the growing process to a changing climate but it is proving tricky.
Mrs Hulme-Oldroyd said: “We are currently doing trials with chilling roots but this will add to the expenses of the process and costs must be kept under control as it is difficult to make it pay as it is.
“This forcing process was tried all over this country in the early 1800s and elsewhere it died out as they simply could not get sufficient yields from the roots to cover the costs of production. I don’t want that to happen here in the Rhubarb Triangle.
“Growers have suffered lower forced yields over the last 10 years as global warming takes hold - soon ‘normal yields’ will be a thing of the past.
“I am worried some of the last 11 growers in the Rhubarb Triangle will find this crop commercially unviable and will grow other things as has happened elsewhere.”
The Rhubarb Triangle once stretched to a larger area including Bradford with over 200 growers during its peak.
Yorkshire forced Rhubarb is recognised by the EU as a regional product and has Protected Designation of Origin status which prevents copycats from marketing their products as being the same.
As well as a dent to local pride, a demise in rhubarb crops would be a major blow, according to grower Janet Hulme-Oldroyd, as she says it has health benefits.
She said: “Research has been done on our forced crops for the last four years, and it shows that forced rhubarb contains massive amounts of plant substances that can help prevent cancer from starting.
“Rhubarb is also a main stay for slimmers as it causes metabolic stimulation; it is good for diabetics and it’s high in calcium.”
Wakefield Festival of Food, Drink and Rhubarb will take place in Wakefield Cathedral Precinct from February 20 to February 22 2015.