The Complete Handbook of Rhubarb

Chapter 1: Understanding Rhubarb

Rhubarb is not a fruit, a vegetable, or a berry, and understanding what it actually is is the first step toward growing, buying, or cooking with it successfully. It is a perennial herbaceous plant in the family Polygonaceae, which makes it a close botanical cousin of buckwheat and sorrel. The part that is eaten is the leaf stalk, or petiole. The large, triangular leaves themselves contain high concentrations of oxalic acid and anthraquinone glycosides, making them toxic to humans and livestock, and they are always discarded.

The cultivated plant you will encounter is almost always a hybrid, primarily derived from Rheum rhabarbarum and Rheum rhaponticum, though the taxonomy has been debated for centuries. For the purposes of any practical user, this distinction is largely academic. What matters is the plant's behavior. A rhubarb plant is a clump-forming perennial that stores energy in a thick, fleshy root system known as the crown. Each spring, buds on the crown break dormancy and produce large leaves on long stalks. The plant spends the growing season photosynthesizing and replenishing the crown's reserves for the following year.

One of the most critical physiological facts about rhubarb is its requirement for winter chilling. The crown must be exposed to a period of cold temperatures, typically below 4.4°C for at least 500 to 700 hours, to break dormancy and initiate normal spring growth. This is not a preference; it is a hard requirement. Growers in mild-winter regions, such as parts of the