UK sales are now worth over £20m a year, some 500 per cent higher than in 2004, with home production increasing by around 200 per cent and imports accounting for the rest.
The main reason for blackberries' increased popularity is the well-publicised health benefits of eating berry fruits, especially the darker-coloured ones, said Hargreaves Plants blackberry specialist Jamie Petchell. Nevertheless, the market for these fruits still lags well behind those for strawberries and raspberries.
Most of the increase in UK production comes from new growers, but Petchell warned that expansion must not be overdone. It is probably best achieved by extending the season rather than producing more in the main season - which traditionally runs August to September.
"The greatest percentage market growth has been from October to May, Mexico being the main producer in this period," Petchell said. "There's no reason why we cannot extend our season. We're developing the world's first primocane varieties (bred by Arkansas university) that will give a big opportunity for early season and double cropping."
Primocane varieties will provide a large proportion of future growth in blackberry production, he predicted. Better eating quality is also important to persuade the 75 per cent of people who had not eaten blackberries over the past year to buy them, he added.
Petchell said that since 2005 Hargreaves has been screening seedlings from the Arkansas breeding programme. The number has increased from about 400 to some 7,000 this year. The best seedlings are being bulked up and will go into growers' trials.
Best of the established varieties from Arkansas is Ouachita, a thornless, mid-season erect type with an average berry size of 6g to 7g with 10 to 11 per cent soluble solids. Its yield compares well with the best Arkansas varieties and it is suited to a wide range of climates.