Rhubarb is an intensely sour vegetable in the genus Rheum which is popular with many people in a cooked and heavily sweetened form as part of a dessert. Traditionally, rhubarb is paired with things like strawberries or ginger, and abundantly sweetened. The result is a tart, sweet, complex flavor which is quite distinctive. The plant has been grown in many parts of the world for thousands of years, and comes into season between April and June. In some regions, it is classified as a fruit, because of how it is used, although this is technically incorrect.
Archaeological evidence suggests that rhubarb has been grown and used medicinally for thousands of years in China. The name of the plant is related to an ancient Greek word meaning “foreign,” and the plant appears to have been imported to Europe by travelers. However it arrived, rhubarb quickly became entrenched in European cuisine, and it continues to play a strong supporting role in many European desserts and preserves.
Only the stalks of rhubarb are edible. Depending on the varietal and how it is cultivated, the stalks will be green to dark red in color, often in streaks. The leaves have a high oxalic acid content, and are potentially toxic to both humans and animals. For this reason, the leaves are trimmed and discarded before rhubarb is cooked. Most commonly, the sour stalks are used in a pie, but rhubarb is also used to make preserves and wines.
Temperate climates are the preferred growing conditions for rhubarb, which will thrive in USDA zones three through eight. The plants are typically sprouted in a greenhouse, and then spaced approximately three feet (91 centimeters) apart in a well tilled, mulched, and composted bed. After planting in the spring, rhubarb is watered thoroughly intermittently and is offered plenty of fertilizer. In the first year of growth, no part of the plant should be harvested, so that the rhubarb establishes a strong root system. In the second year, stalks can be cut for one to two weeks, and in the third year, rhubarb can be harvested for the entire growing season. As a general rule, no more than one third of the plant should be cut at once.
After cutting, rhubarb is very fragile. It can be wrapped tightly in plastic and stored for up to three days under refrigeration, but after that, the plant needs to be used. Be aware of this when picking out rhubarb in the store, and look for firm, crisp stalks with no pitting or marked discoloration. Remember to trim the leaves off before use, and to utilize the unique sour flavor of rhubarb in a way which will showcase it, rather than just trying to cover it up.