Rumex acetosa This is a fantastic perennial salad green which can also be cooked. It has a distinct lemon flavour which in older leaves can be quite tart. Cutting down older leaves and seed heads promotes nice young fresh growth which has the best flavour. Clump forming and very hardy it is a winter salad must have which is high in vitamin A and C. Sorrel is high in oxalic acid and not suitable for those prone to developing kidney stones. Eat in moderation. Sometimes seen as a weed though I have not found this in my own garden where it has just slowly clumped for 3 years. Plant in a pot if your concerned. A quick google search brings up loads of recipes. Perennial, 50cm