Dried tarragon

Dried tarragon is the leaf of Artemisia dracunculus var. sativa, French tarragon, a sterile perennial of the daisy family that never sets viable seed and must be propagated exclusively by root division or stem cuttings -- a botanical quirk that has kept it scarce, expensive and impossible to industrialise the way you can flood a field with basil seed. The essential oil is dominated by estragole (methyl chavicol), running 60 to 75 percent of total volatiles, the compound responsible for the sweet anise-liquorice note that defines the herb; behind it sit ocimene, limonene, and trace methyleugenol. The French type (var. sativa) is the only one worth cooking with: its flavour is clean, complex and suffused with that green-anise sweetness that Harold McGee called 'the most distinctively French of all herb flavours.' Russian tarragon (var. dracunculus), which does set seed and can be sown like grass, is a coarser, bitter, nearly flavourless impostor that floods cheap spice racks and disappoints everyone who plants it expecting bearnaise. Mexican tarragon (Tagetes lucida, a different genus entirely) is a serviceable substitute in warm climates where French tarragon refuses to grow. Two origins matter: the Drome valley in southeastern France, where the herb has been cultivated since the sixteenth century and where the terroir of warm days, cool nights and alluvial gravel produces the benchmark essential-oil profile; and the Caucasus, particularly Georgia, which is the plant's original homeland and still exports significant volume. Culinary cornerstones: bearnaise sauce (tarragon is the defining herb, infused in the shallot-vinegar reduction), the fines herbes quartet (tarragon, chervil, parsley, chives), tarragon vinegar (a pantry staple of classical French cooking), poulet a l'estragon (roast chicken with tarragon cream), and ravigote sauce.