In the kitchen a herb is the leaf of a plant, used fresh or dried for its flavour and aroma; botanists and herbalists use the word more widely.
The short answer¶
In cooking, a herb is the leaf of a plant used in small amounts for its flavour and aroma rather than as a vegetable in its own right. Basil, parsley, mint, thyme and bay are herbs. The same plants' seeds, roots or bark, dried, would usually be called spices.
The rule of thumb is leaf = herb, everything else = spice. It works most of the time, and the exceptions are part of what makes the subject interesting.
Three meanings of one word¶
"Herb" is used in three different ways, and they do not line up.
| Sense | A herb is… | So, for example |
|---|---|---|
| Culinary | a leaf used to season food | Rosemary is a herb, though it is a woody shrub |
| Botanical | a plant with no woody stem above ground, which dies back after flowering or at the end of the season | A banana plant is technically a herb; rosemary is not |
| Herbal medicine | any plant, or part of one, used for health | Roots, barks and seeds all count |
This site uses the culinary sense throughout. The word itself comes from the Latin herba, grass or green plant. In British English the h is pronounced; in American English it usually is not, which is the older pronunciation: the h was silent in English for centuries.
Soft herbs and woody herbs¶
Cooks divide herbs by the plant they come from, because that decides how they behave in the pan.
- Soft herbs — basil, coriander, parsley, dill, chervil, chives, tarragon, mint. Tender leaves whose aroma fades with heat. Add them at the end, or raw, and chop them with a sharp knife so they cut rather than bruise.
- Woody herbs — rosemary, thyme, sage, bay, oregano. Tougher, oilier leaves on hard stems. They stand up to long cooking, go in early, and dry well.
The distinction also predicts which herbs keep their character when dried: woody herbs mostly do, soft herbs mostly do not. See fresh vs dried herbs.
Where the flavour comes from¶
A herb's scent is carried in volatile oils. In the mint family (Lamiaceae) — basil, mint, thyme, rosemary, sage, oregano, marjoram — the oil sits in tiny glands on the surface of the leaf, which is why brushing past a rosemary bush is enough to smell it. In the carrot family (Apiaceae) — parsley, coriander, dill, chervil, lovage — it runs in fine canals through the leaf and stem.
Either way, the oil is released when the leaf is crushed, chopped or warmed, and it escapes into the air just as readily. That is why herbs are torn or chopped just before use, and why a jar of dried herbs loses its scent faster than a jar of whole spices. See aroma compounds.
Most culinary herbs come from those two families. The rest are scattered: chives are an allium, tarragon is in the daisy family, bay is a laurel, and curry leaves come from a small tree in the citrus family.
The grey areas¶
- One plant, two ingredients. Coriander leaf is a herb and coriander seed a spice; the same goes for dill and dill seed, and for fennel fronds and fennel seed.
- Leaves from trees. Bay, curry leaves and makrut lime leaves come from trees but are used exactly like herbs, so they are filed as herbs.
- Not quite leaves. Lemongrass is the lower stem of a grass, and chives are hollow leaves of an onion relative. Both are treated as herbs.
- Leaves as vegetables. Sorrel, rocket and watercress sit on the line between herb and salad; it depends on how much of them goes in.
How to use herbs well¶
- Match the herb to the timing. Woody herbs at the start, soft herbs at the end.
- Use enough. A sprig of parsley is garnish; a big handful, as in a tabbouleh or a salsa verde, is flavour.
- Buy or grow them fresh where you can. Soft herbs in particular are at their best within a day or two of picking. See planning a herb garden and growing herbs indoors.
- Dry the ones that suit it. See drying herbs.