All parts of the coriander plant are edible, but the fresh leaves and the dried seeds are the most commonly used in cooking. Coriander is commonly used in Middle Eastern, Mediterranean, Indian, South Asian, Latin American, Chinese, African and Southeast Asian cuisine.
The leaves are variously referred to as coriander leaves, cilantro (in the United States, from the Spanish name for the plant), dhania (in the Indian subcontinent, and increasingly in Britain). The leaves, and especially the stems, have a very different taste from the seeds, similar to parsley but "juicier" and with citrus-like overtones. Some people instead perceive an unpleasant "soapy" taste and/or a rank smell. This is believed to be a result of an enzyme that changes the way they taste coriander leaves, a genetic trait, but has yet to be fully researched.
The fresh leaves and stems are an essential ingredient in many Vietnamese foods, Asian chutneys, Mexican salsas and guacamole, and occasionally is used in sushi rolls. Chopped coriander leaves are also used as a garnish on cooked dishes such as dal and many curries. As heat diminishes their flavour quickly, coriander leaves are often used raw or added to the dish right before serving. Although, in some Indian and Central Asian recipes, coriander leaves are used in huge amounts and cooked till they dissolve into sauce and their flavour mellows.
Another factor that dictates the quality of flavor is the time when coriander is harvested. If its roots consistently stay at a temperature above 75 degrees Fahrenheit, the herb will quickly bolt, causing its leaves and stems to yield a bitter flavor and become quite chewy. At this point, made evident by the thinner and finer leaves, it is only practical to harvest the coriander seeds, since the stems and leaves are no longer a usable food source.
Coriander leaves were formerly common in European cuisine but nearly disappeared before the modern period. Today Europeans usually eat the leaves and stems only in dishes that originated in foreign cuisines, except in Portugal, where it is still an essential ingredient in many traditional dishes.
The fresh coriander herb is best stored in the refrigerator in airtight containers, after chopping off the roots. The leaves do not keep well and should be eaten quickly, as they lose their aroma when dried or frozen.