Field-grown rhubarb will shortly be coming into season and appearing in supermarkets in the UK, so it seems like a good time to take a look at the chemistry behind this odd-looking vegetable. It’s mostly used in pies and desserts, but it’s only the stalks of the plant that we eat – and there’s a reason for that. This graphic takes a look at why, and also looks at the chemical compounds that contribute to the colour and the laxative effect of rhubarb.