I picked and stewed the first rhubarb of the year from the garden this morning. Hopefully, our two patches will keep us self-sufficient in rhubarb over the summer, as I am very partial to it.
Technically, Rheum rhabarbarum is a vegetable, and it has historically been used as such in Asia and Poland. It is native to Siberia or thereabouts. The only edible part of the plant is the stalk, which has a distinctively high acidity (2.0-2.5%) and a particularly high but harmless concentration of oxalic acid. The leaves are poisonous because of a dangerously high concentration of oxalic acid and other chemicals (McGee, 2004).
Niki Segnit notes, in The Flavour Thesaurus (2010), that the intense sourness of rhubarb needs to be countered with sufficient sugar, “then the flavour becomes fascinating – a combination of aromatic, candied strawberry notes with a cooked-apple fruitiness, plus a strong thick note redolent of a greenhouse full of ripening tomatoes.” Among the flavour combinations she suggests are rhubarb and almond, rhubarb and mango, rhubarb and vanilla, and rhubarb and cucumber. The latter mixes rhubarb and cucumber with salt; an Iranian salad, for example, adds rocket leaves, lemon juice and a little mint just before serving.
Harold McGee on Food and Cooking (2004). Hodder & Stoughton. Page 367.
Niki Segnit (2010) The Flavour Thesaurus. Bloomsbury. Pages 254-256.