Sour notes

IT is the season of the sour, when gooseberries, rhubarb and sorrel come into their own.

- Mark Diacono

I look forward to it every bit as much as asparagus, new potatoes and other seasonal markers of the kitchen garden. Sorrel is perhaps the least appreciated of the three, taking its name from the French surelle, from sur meaning 'sour' and, as with rhubarb, that sharpness is due to oxalic acid. Sorrel is closely related to wild dock, and is similarly easy to find throughout Europe and North America, where it grows predominantly in woodlands and open fields. It has a long history of culinary and medicinal use, stretching back as least as far as the ancient Egyptians, Greeks and Romans, who enjoyed it as a digestive before and after meals. As with dock, its leaves ease stings.

Wild sorrel (Rumex acetosa) resembles a slender, smaller dock and can be deliciously tender (especially early in the season) or tough and fibrous; thankfully, improved varieties reward more reliably in flavour and texture. The improved broad-leaved sorrel and the elegant 'Red veined' (Rumex sanguineus var. sanguineus) are reliably excellent, but the pale grey-green-blue buckler-leaved sorrel (