The thick, celerylike stalks of this buckwheat-family member can reach up to 2 feet long. They're the only edible portion of the plantthe leaves contain oxalic acid and can therefore be toxic. Though rhubarb is generally eaten as a fruit, it's botanically a vegetable. There are many varieties of this extremely tart food, most of which fall into two basic typeshothouse and field grown. Hothouse rhubarb is distinguished by its pink to pale red stalks and yellow-green leaves, whereas field-grown plants (which are more pronounced in flavor) have cherry red stalks and green leaves. Hothouse rhubarb is available from around December to March, while the field-grown plant can usually be found from March to October, with a peak from April to June. Choose crisp stalks that are brightly hued. The leaves should be fresh-looking and blemish-free. Highly perishable, fresh rhubarb should be refrigerated, tightly wrapped in a plastic bag, for up to 3 days. Wash and remove leaves just before using. Because of its intense tartness, rhubarb is usually combined with a considerable amount of sugar. It makes delicious sauces, jams and desserts and in some regions is also known as pieplant because of its popularity for that purpose. In America, a traditional flavor combination is rhubarb and strawberries; in Britain, rhubarb and ginger. Rhubarb contains a fair amount of vitamin A.