Herbs and spices: what actually separates them

Cooks separate herbs from spices because the two behave differently in a pan, and that practical difference is what the words are really tracking. Herbs are soft leafy tissue with volatile aromatics held loosely: they give up their flavour fast, they suffer from long cooking, and many are best added at the end or used fresh. Spices are dense storage tissue — seeds, bark, roots, dried fruit — where the aromatics sit inside a protective structure. They tolerate and often require heat, fat and time.

That is why the rule earns its keep despite being imprecise. Knowing that basil is a herb tells you to add it late; knowing that cumin is a spice tells you to bloom it in oil first. The category is doing real work about technique, not taxonomy.

The dried-versus-fresh axis is a separate question that often gets folded into this one. Most spices are used dried because that is how the trade moves them and how they keep; most herbs are available fresh and are diminished by drying. But dried herbs are still herbs, and fresh ginger is still a spice.

Spices come from nearly every part of a plant except the leaf, and the range is wider than most people expect. Seeds give cumin, coriander, fennel, caraway, nigella, celery seed and mustard. Dried fruits give black pepper, allspice, juniper, sumac, star anise and every chilli. Bark gives cinnamon and cassia. Roots and rhizomes give ginger, turmeric and galangal. Flower parts give saffron, which is a stigma, and cloves, which are unopened flower buds. Aril — the lacy covering of a seed — gives mace. Resin gives asafoetida.

Herbs are the leaves, and sometimes the soft stems: oregano, thyme, basil, mint, parsley, sage, rosemary, marjoram, savory.

Two entries in this dataset are useful because they sit awkwardly. Bay leaf is a leaf, which makes it a herb by the rule, and it is sold, stored and used exactly as a spice — dried, whole, added early, simmered for hours. Za'atar herb is a leaf too, and the word za'atar also names a blend containing sesame and sumac, so the same term covers a herb and a spice mixture depending on who is speaking.

The clearest evidence that the boundary is culinary rather than botanical is that a single plant can supply both. Coriandrum sativum gives coriander leaf, a herb used fresh and added late, and coriander seed, a spice that is toasted and ground. They taste almost nothing alike — the leaf is citric and soapy to some people because of specific aldehydes, the seed is warm and orange-peel sweet — and a recipe calling for one and made with the other fails completely.

Dill does the same: dill weed is the feathery leaf, dill seed is the fruit, and they are sold separately because they are not interchangeable. Fennel gives leaf, seed and a bulb vegetable from one species.

Nothing in botany explains why we call one part a herb and the other a spice. The plant does not change; the tissue does, and the cook responds to the tissue.

There is no botanical rank called "spice". Botany classifies by evolutionary relationship, not by use, and the spice shelf cuts straight across that: pepper is a vine fruit, cinnamon a tree bark, saffron a crocus stigma, asafoetida a root resin. Their only shared property is that people dry them and use them in small quantities for flavour. That is a description of human behaviour, not of plants.

A stricter definition sometimes offered — that spices are aromatic parts of tropical plants and herbs come from temperate ones — fails immediately on caraway, juniper and celery seed, all temperate, and on the fact that many herbs grow across both zones.

It is also worth separating both from a third category the words often absorb: aromatic vegetables like garlic and onion, and seasonings like salt. Garlic is used like a spice, sold dried and powdered like a spice, and is a bulb vegetable. Salt is a mineral and not a plant at all.

English keeps herbs and spices in separate boxes; several other languages do not, and translated recipes carry the difference across. The Arabic word za'atar names a wild Levantine herb, the dried blend made with it, and in some places oregano and thyme generally. Hindi has distinct everyday words for individual spices but no clean single equivalent of the English herb-and-spice split as a pair of categories.

Regional English differs too. "Mixed herbs" and "mixed spice" name two entirely different British supermarket products, one savoury and leafy and one sweet and ground, and neither name would be predictable from the ingredients.

None of this is a problem to be solved. It is a reason to read a recipe for what it is asking the ingredient to do rather than for which category it belongs to.