Most people perceive the taste of coriander leaves as a tart, lemon/lime taste, but a smaller group of about 3–21% of people tested think the leaves taste like dish soap, linked to a gene which detects some specific aldehydes that are also used as odorant substances in many soaps and detergents.
Coriander is native to regions spanning from Southern Europe and Northern Africa to Southwestern Asia. It is a soft plant growing to 50 cm (20 in) tall. The leaves are variable in shape, broadly lobed at the base of the plant, and slender and feathery higher on the flowering stems. The flowers are borne in small umbels, white or very pale pink, asymmetrical, with the petals pointing away from the center of the umbel longer (5–6 mm or 0.20–0.24 in) than those pointing toward it (only 1–3 mm or 0.039–0.118 in long). The fruit is a globular, dry schizocarp 3–5 mm (0.12–0.20 in) in diameter. Pollen size is approximately 33 microns.
Although native to Iran, coriander grows wild over a wide area of Western Asia and Southern Europe, prompting the comment: "It is hard to define exactly where this plant is wild and where it only recently established itself." Fifteen desiccated mericarps were found in the Pre-Pottery Neolithic B level of the Nahal Hemar Cave in Israel, which may be the oldest archaeological find of coriander. About half a litre of coriander mericarps was recovered from the tomb of Tutankhamen, and because this plant does not grow wild in Egypt, Zohary and Hopf interpret this find as proof that coriander was cultivated by the ancient Egyptians.
The dry fruits are known as coriander seeds. The word "coriander" in food preparation may refer solely to these seeds (as a spice), rather than to the plant. The seeds have a lemony citrus flavour when crushed, due to terpenes linalool and pinene. It is described as warm, nutty, spicy, and orange-flavoured.
Coriander is commonly found both as whole dried seeds and in ground form. Roasting or heating the seeds in a dry pan heightens the flavour, aroma, and pungency. Ground coriander seed loses flavour quickly in storage and is best ground fresh. Coriander seed is a spice in garam masala and Indian curries which often employ the ground fruits in generous amounts together with cumin, acting as a thickener in a mixture called dhana jeera. Roasted coriander seeds, called dhana dal, are eaten as a snack. They are the main ingredient of the two south Indian dishes sambhar and rasam.
Raw coriander leaves are 92% water, 4% carbohydrates, 2% protein, and less than 1% fat (table). The nutritional profile of coriander seeds is different from the fresh stems or leaves. In a 100 gram reference amount, leaves are particularly rich in vitamin A, vitamin C and vitamin K, with moderate content of dietary minerals (table). Although seeds generally have lower content of vitamins, they do provide significant amounts of dietary fiber, calcium, selenium, iron, magnesium and manganese.
Different people may perceive the taste of coriander leaves differently. Those who enjoy it say it has a refreshing, lemony or lime-like flavor, while those who dislike it have a strong aversion to its taste and smell, characterizing it as soapy or rotten. Studies also show variations in preference among different ethnic groups: 21% of East Asians, 17% of Caucasians, and 14% of people of African descent expressed a dislike for coriander, but among the groups where coriander is popular in their cuisine, only 7% of South Asians, 4% of Hispanics, and 3% of Middle Eastern subjects expressed a dislike.
Some people are allergic to coriander leaves or seeds, having symptoms similar to those of other food allergies. In one study, 32% of pin-prick tests in children and 23% in adults were positive for coriander and other members of the family Apiaceae, including caraway, fennel, and celery. The allergic symptoms may be minor or life-threatening.