Oregano

Oregano (Origanum vulgare), also known as wild marjoram, is a flowering plant in the mint family (Lamiaceae). It originally comes from the Mediterranean region but has spread widely across the temperate Northern Hemisphere, especially in the United States and Mexico. This woody perennial can reach about 90 cm (35 in) tall, with opposite leaves 1–4 cm (0.5–1.5 in) long that are covered in tiny hairs (trichomes). Young stems are square and hairy, turning woody as they age. In summer, it produces clustered, upright spikes of small flowers—white, pink, or light purple—each 3–4 mm (0.12–0.18 in) long.

The word "oregano" comes from Spanish *orégano*, which traces back to Latin *orīganum* and then to Classical Greek *ὀρίγανον* (orī́ganon). The ultimate origin is debated: some think it combines Greek *ὄρος* (óros, "mountain") and *γάνος* (gános, "joy"), but the Oxford English Dictionary suggests it is likely a loanword since the plant originates from Africa.

Oregano is a perennial, though in colder climates it is often grown as an annual because it may not survive winter. It spreads to about 50 cm (20 in) wide. Its leaves are spade-shaped and olive-green. The flowers, which appear in clusters 4–7 cm (1.5–2.75 in) long, can be purple, pink, or white. It is closely related to marjoram, which is why it is sometimes called wild marjoram.

Chemically, oregano contains polyphenols, including various flavones. Its essential oil is mostly made up of monoterpenoids and monoterpenes, with concentrations varying widely by geographic origin. Over 60 compounds have been identified; the main ones are carvacrol and thymol (sometimes over 80%), along with lesser amounts of p-cymene, γ-terpinene, caryophyllene, spathulenol, germacrene D, β-fenchyl alcohol, and δ-terpineol. Drying the plant reduces both the quantity and distribution of these volatile compounds—higher heat and longer drying times cause greater losses. For example, fresh whole plant material containing 33 g/kg dry weight (3.1 g/kg wet) dropped to less than a third after warm-air convection drying. Volatile compound concentrations are highest near the end of the growing season.

Over centuries, many subspecies and strains have been developed for different flavors, ranging from spicy or astringent to sweet and complex. Common garden oregano sold as *O. vulgare* often has a bland taste and larger, less dense leaves, making it less desirable for cooking. It can cross-pollinate with better strains, but the offspring are rarely superior. Related species *Origanum onites* (from Greece and Turkey) and *O. syriacum* (from West Asia) have similar flavors. Marjoram from Turkey is closely related but tastes quite different because its essential oil lacks phenolic compounds. Some varieties have a flavor that falls between oregano and marjoram.

Accepted subspecies include: *O. v. subsp. glandulosum* (Tunisia, Algeria); *O. v. subsp. gracile* (Central Asia, Iran, India, Turkey, Afghanistan, Pakistan)—it has glossy green leaves, pink flowers, a pungent, spicy flavor, and is often grown for ornament; *O. v. subsp. hirtum* (Italian or Greek oregano, from Greece, Balkans, Turkey, Cyprus)—vigorous, hardy, with darker green, slightly hairy leaves, and considered the best all-purpose culinary subspecies; *O. v. subsp. virens* (Iberian Peninsula, Macaronesia, Morocco); *O. v. subsp. viridulum* (from Corsica to Nepal); and *O. v. subsp. vulgare* (widespread from Ireland to China, naturalized in North America and Venezuela).

Notable cultivars include: 'Aureum'—golden foliage (greener in shade), mild taste, and winner of the Royal Horticultural Society's Award of Garden Merit; 'Greek Kaliteri'—a strain of *O. v. subsp. hirtum* with small, hardy, dark, compact leaves that are silvery-haired and often purple underneath, known for strong, archetypal oregano flavor; 'Hot & Spicy'—another *O. v. subsp. hirtum* strain; and 'Nana'—a dwarf cultivar. Cultivars sold as Italian or Sicilian oregano are usually hardy sweet marjoram (*O. × majoricum*), a hybrid between *O. v. subsp. hirtum* and sweet marjoram (*O. majorana*). These have sweet, spicy tones with little bitterness and are prized for cooking.

Oregano is planted in early spring, spaced about 30 cm (12 in) apart in fairly dry soil with full sun. It tolerates a pH range from 6.0 (mildly acidic) to 9.0 (strongly alkaline), preferring 6.0 to 8.0. It does best in a hot, relatively dry climate but can adapt to other conditions.

Culinarily, oregano is used for the flavor of its leaves, which often become more intense when dried. Along with sweet marjoram, it is a common culinary herb. Though once used in folk medicine, there is no clinical evidence that oregano provides any health or anti-disease effects. It is also grown as an ornamental plant, with many cultivars bred for different leaf colors, flower colors, and growth habits.