Cilantro, or Chinese parsley, is the name given to the leaves of the coriander plant (Coriandrum sativum), while both the plant and the seed-like fruit are traditionally called coriander. This is changing, as many people who use the herb may be unaware that the plant yields another spice and refer to the entire plant as cilantro. Culantro, which refers to a different herb altogether, is sometimes mistakenly used to refer to coriander leaves. The coriander plant is in the same family, Apiaceae, as anise, fennel, dill, caraway, and cumin.
Initially, the coriander plant has leaves like parsley, to which it is related. When the plant bolts, producing a stalk on which flowers will grow, the leaves it produces are very different in nature and no longer as desirable. As a result, two different strains have been developed — plants that are slow-bolting and produce better leaves, and plants that are encouraged to bolt to produce flowers and fruit. When it does bloom, the plant has small white or pink flowers, and when grown for the spice coriander, it grows to an average height of 2 feet (60 cm), though it can get bigger.
The plant is a hardy annual that does not transplant well because of its taproot. When growing it for cilantro, one way of dealing with its tendency to bolt it to use succession planting and protect it from extreme heat. Also, if a gardener is growing the plant for its leaves, the sudden production of a long, tall stalk indicates the plant's intent to flower.
Cilantro is used as a garnish in Southeast Asian food, and as an ingredient of Thai green curry paste. In Mexico, it is used in salsa and guacamole. When used in cooking, the leaves should be added in the last few minutes so they don't lose their flavor.
Some people suggest pulling up the whole plant by the roots when bolting becomes imminent, but it doesn't stay fresh very long or dry well, so freezing is the best option. Growers can pack clean, dry leaves into ice cube trays, cover them with water, then freeze them, sealing the cubes in plastic bags when they're ready. Cooks can also make a sort of pesto by grinding up the leaves with garlic and a touch of salt, the wrapping the paste well and freezing it.
The coriander plant was grown in the Hanging Gardens of Babylon. The leaves are an ingredient in the bitter herbs or maror that are a traditional part of the Passover meal.