Oregano: Flavor, Chemistry, Species and How to Use It

Oregano is the warm, pungent herb that makes a pizza sauce taste like pizza sauce. It also fared worst in Europe’s largest survey of herb and spice fraud, where 48% of oregano samples were suspicious, mostly because of olive leaves.¹ The real thing is the dried or fresh leaf of Origanum vulgare and its close relatives, perennial herbs of the mint family. But “oregano” is a flavor category too: the jar on your shelf may come from several Origanum species, and Mexican oregano comes from a different plant family altogether.

At a glance

What oregano is

The plants sold as oregano

Common oregano, Origanum vulgare, is a perennial of the temperate biome in the mint family, Lamiaceae. In mild climates it’s usually grown as a small evergreen subshrub. Kew accepts six subspecies, including subsp. hirtum, subsp. glandulosum and subsp. vulgare.

The name stretches well past that one species. A 2020 review of oregano chemistry notes that “oregano” gets used for several other Origanum species, like O. onites and O. majorana, and even for plants in other genera: Thymus, Satureja, Lippia and Coridothymus.² The Codex standard for dried oregano reflects this. It covers any Origanum species except marjoram (Origanum majorana), plus Lippia species traded as Mexican oregano.³

• Mexican oregano. It’s Lippia graveolens, in a different family, the Verbenaceae. Kew now treats Lippia graveolens as a synonym of Lippia origanoides, a shrub native from the southwestern United States (Texas, New Mexico) through Mexico and Central America to Argentina and Uruguay.⁴ See Mexican oregano and Mexican oregano vs. oregano.
• Marjoram. Origanum majorana is in the same genus, native to southern Türkiye and Cyprus. Confusingly, Britannica lists “wild marjoram” and “European marjoram” as other names for oregano.⁵ See marjoram and marjoram vs. oregano.

Name

“Oregano” comes from the Greek oros, “mountain,” and ganos, “brightness” or “joy.”

Flavor and aroma

Good dried oregano smells warm, resinous and a little camphor-like. It tastes pungent and slightly bitter, and strong lots have a sharpness that can numb your tongue a little. Greek and Italian culinary oreganos have a strong aroma and a warm, pungent taste. Even so, the University of Delaware’s extension service puts oregano in its medium-strength group, not with dominant herbs like sage or rosemary.⁶

The compounds

Thymol and carvacrol are among the constituents of oregano’s essential oil. A 2020 review in the International Journal of Molecular Sciences calls them the two primary phenols, together making up almost 78–85% of the oil.² That share swings widely from plant to plant:

The review explains why one number can’t cover all oregano. The southern subspecies (hirtum, glandulosum, gracile) carry more essential oil, dominated by carvacrol, thymol, p-cymene and γ-terpinene. Lower-oil plants are marked instead by sabinene, linalool, borneol and sesquiterpenes, and northern subspecies are poorer in essential oil overall. The review also links falling oil content at higher altitude to fewer peltate glands on the leaf, and notes that Greek oregano has denser, larger peltate trichomes than common oregano.² Keep in mind these are all essential-oil figures. We found no measured carvacrol content for the dried leaf you actually cook with.

Origin and history

Kew gives the native range of O. vulgare as Macaronesia to China, spanning most of Europe, North Africa, the Caucasus, Central Asia, the Himalaya and parts of China. It’s also recorded as introduced in many US states and Canadian provinces, from California to Québec. The culinary oreganos come from the hills of the Mediterranean countries and western Asia.

Britannica records that the Greek physician Hippocrates documented oregano’s use as an antiseptic. It also says oregano became widely known in the United States after World War II, when returning soldiers who’d developed a taste for Italian food made it popular.⁵ We couldn’t trace the “pizza herb” nickname that often comes attached to that story to a source.

How oregano is used

Oregano is a key ingredient in Mediterranean and Middle Eastern cooking, used with meat, vegetables, sauces and soups, and essential in Italian pizza and pasta sauces, Greek salads and gyros.

• Italy and Italian-American cooking. Pizza and tomato sauces are the defining uses. See good spices for pizza and Italian seasoning.
• Greece. Greek salad and gyros. Dried oregano also goes into lemon and olive oil dressings for grilled meat and fish. See Greek seasoning.
• Mexico and the US Southwest. Mexican oregano is the usual pick in Mexican cooking. In the US, the federal purchasing spec for chili powder lists oregano alongside ground chili pepper, cumin, salt and garlic powder.⁷ See chili powder.
• Middle East. See also za’atar, a related family of herb blends.

Technique

Oregano is one of the hearty herbs you add early in cooking. The University of Delaware notes that dried herbs are stronger than fresh and suggests crushing them to release their oils in quick and medium-length dishes. Its rough equivalence is 3/4 to 1 teaspoon dried crumbled herb for 2 to 3 teaspoons fresh. For medium-strength herbs, it suggests starting with 1 to 2 teaspoons for six servings.⁶ More in fresh oregano vs. dried, oregano uses and cooking with oregano. Overdid it? See too much oregano.

Buying and quality

The Codex standard for dried oregano (CXS 342-2021) sets three grades for whole and crushed oregano and one for ground, plus a 12% moisture maximum for all styles.³ The key chemical limits, on a dry basis:

Foreign matter is capped at 0.1% for every whole grade, and no live insects are allowed in any style.³ At the store, a dull, dusty jar with little smell when you rub it is the warning sign.

Adulteration

Oregano fared worst in the European Commission’s 2019–2021 coordinated control plan on herb and spice fraud, which tested 1,885 samples of six herbs and spices from 21 EU countries plus Norway and Switzerland.¹ Across all six products, 17% of samples were suspicious. For oregano it was 48%, mostly because of olive leaves. The Joint Research Centre’s report calls the oregano supply chain the most vulnerable of those tested.⁸ Buying whole or crushed leaf instead of fine powder makes foreign leaf easier to spot.

Storage

We found no published shelf-life figure for dried oregano from a regulator or standards body. Like other dried herbs, its flavor lives in a volatile oil, so your nose is the test: crush a pinch, and if the smell is faint, it’s faded. For fresh sprigs, see can you freeze oregano? and how to dry oregano.

Nutrition

A teaspoon of dried oregano leaves weighs 1.0 g. At that weight it gives you about 6 µg of vitamin K (5% of the FDA Daily Value), 0.37 mg of iron (2%), 16 mg of calcium (1%) and 0.4 g of fiber. We worked those out from USDA’s per-100 g values of 622 µg vitamin K, 36.8 mg iron, 1,600 mg calcium and 42.5 g fiber, against Daily Values of 120 µg, 18 mg and 1,300 mg.⁹¹⁰ At normal seasoning amounts, oregano isn’t a meaningful source of any nutrient.

Safety

• Pyrrolizidine alkaloids. The EU sets a maximum of 1,000 µg/kg for these plant toxins in dried oregano, marjoram, borage and lovage, and in mixtures made only of them. For other dried herbs the limit is 400 µg/kg.¹¹
• Health claims. Thymol and carvacrol are known for antibacterial properties.⁵ That’s a property of the isolated compounds, not evidence that eating oregano treats infection. The NIH’s National Center for Complementary and Integrative Health has no fact sheet on oregano.¹² Claims that oregano or its oil treats colds, infections such as MRSA, or cancer rest on lab work at most, and we’re not making them here.

Substitutes and comparisons

Marjoram is the closest stand-in, though milder and sweeter. Thyme shares oregano’s phenolic character. Mexican oregano works in most dishes but leans citrusy. See oregano substitutes and Mexican oregano substitutes, plus these comparisons:

• Marjoram vs. oregano
• Oregano vs. thyme
• Basil vs. oregano
• Oregano vs. mint
• Oregano vs. parsley
• Cilantro vs. oregano