Rhubarb is a thick, celery-like plant with red stalks that can grow to be more than two feet long. The red and green stalks are the edible portion of the rhubarb and the leaves, which contain oxalic acid, are not edible. The color of the plant can vary widely from an extremely dark red to a pale reddish-green. Hothouse grown rhubarb tends to be lighter in color than field-grown rhubarb, and has a slightly milder flavor to it, though all rhubarb is extremely tart and has a bright, lemony flavor to it. Rhubarb is seasonal and is typically available from April – June, although it can be grown in hothouses (also known as “forced” rhubarb) for a longer growing season.
Rhubarb is classified as a fruit in the US, although it is botanically a vegetable, and is often used in the same culinary applications as berries and other fruits are. Rhubarb is not usually eaten raw, and is almost always cooked, baked or stewed with other ingredients. Since it is so tart, it requires that a lot of sugar be used to balance its flavor and that makes it a popular base for pies, cobblers, jams and preserves, all of which can handle a lot of sugar. Because of its tart flavor, rhubarb is also often paired with other red fruits, such as strawberries, to lend some additional sweetness to it.
When choosing rhubarb, look for crisp, unblemished stalks and leaves that look fresh, not wilted. Although you do not eat them along with the stalk, the leaves are still and good indicator for freshness.