Crossword clue: a plant (rheum rhaponticum) the leafstalks of which are acid, and are used in making pies; the garden rhubarb.
1 answer found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).
Possible answers
long pinkish sour leafstalks usually eaten cooked and sweetened