Waitrose is to offer its customers a range of naturally black fruit and vegetables, which will be launched in the run-up to Hallowe'en.

It has sourced black varieties of cabbage, potato and pear from British growers, and is planning to make them available for the rest of the season.

Shetland Black potatoes are already on sale in some stores and, according to the supermarket, are proving very popular with shoppers despite the hefty £1.89/kg price tag.

The potatoes are a small, indigenous variety with a blue-black skin and can be baked or roasted. Less prolific than some commercial varieties, they are hardy and slightly more resistant to blight. Once the principal crop on the Scottish islands and with a history dating back to the 1920s, they have since been replaced by other varieties and pushed to the brink of extinction. However, specialist potato supplier Solanum has kept the variety alive and now grows it near St Andrews, Fife, on the mainland.

Vegetable buyer Peter Cooke said: "We have seen a real trend towards heritage varieties that deliver flavour and at the same time reflect historic culinary traditions."

The black cabbage on offer is the Cavolo, which is popular elsewhere in Europe.

It is now being grown in East Anglia and will be sold in Waitrose stores until January next year, priced at £1.19 for 200 grams.

Black Worcester pears, grown for their culinary properties and versatility, will also be stocked. Set to debut in November, they will cost £1.69 per punnet.

Examples of these fruit are grown at the National Fruit Collection at Brogdale, Kent, along with 3,500 varieties of apple, pear and plum to preserve traditional UK varieties for possible commercial cultivation by future generations.

Waitrose said that the idea behind sourcing unusual produce not sold by other retailers is to provide customers with greater choice and variety.