Culantro is not cilantro. It has long leaves with tapered tips and serrated edges. When it comes to flavor, culantro is like cilantro, times ten.
In warmer climates, above Zone 7s, the actual cilantro plant can be reseeded and grown commercially, harvesting the leaves as they appear. In zone 7, and below, the climate is seasonally ideal for Cilantro so many people buy the plant expecting it to bear leaves for an extended period, but it will not. The reason is true cilantro, in heat, is working to expend it's energies to go to seed, coriander. Leaves are herbs, seeds are spices as a general rule in understanding the difference between the two.
The solution to a perennial heat bearing cilantro is the plant, Culantro - Ergyngium foetidum. Culantro is a biennial herb grown throughout the Caribbean and Central America, and is a key ingredient in Puerto Rican cooking. It is relatively unknown in the United States, and is often mistaken for its relative cilantro (Coriandrum sativum L.). It is also known by many other names, such as Puerto Rican coriander, Black Benny, saw leaf herb, Mexican coriander, Saw tooth coriander, long coriander, Spiny coriander, Fitweed, and spiritweed. In Puerto Rico it is known as recao. When cultivated, culantro has a strong, aromatic scent that fills the air when you brush up against it.
Culantro can be planted in pots or on the ground. If planted in the ground, this herb will continue to reproduce for an almost endless supply. Culantro is relatively pest and disease free. It is rumored to be attractive to beneficial insects such as ladybugs, green lacewings, and to provide an excellent defense in the garden against aphids. In cooking it is used to flavor salsa, softrito, chutney, ceviche, sauces, rice, stews, and soups. To harvest, remove the oldest leaves all the way down to the base of the plant leaving the young new leaves to grow. The leaves can be chopped and used fresh or frozen to keep their flavor. Although used in small amounts, its very strong flavor is used as a seasoning in a wide range of foods, including meats, vegetables, and chutneys. Because of this aroma similarity the leaves are used interchangeably in many food preparations and is the major reason for the misnaming of one herb for the other. In Asia, culantro is most popular in Thailand, Malaysia, and Singapore where it is commonly used with or in lieu of cilantro and topped over soups, noodle dishes, and curries.
Unlike cilantro, culantro doesn't bolt, it will produce seeds, but the foliage stays aromatic and tasty. It is a tender perennial that can be wintered over in a pot or cut back and mulch over in the fall.
Culantro is the answer for those who enjoy cilantro but live in a hot/warm climate and want fresh all spring/summer and fall.