Fenugreek is a legume that the world treats as a spice, a herb, and a vegetable, and it is one of very few plants to be all three at once in a single kitchen. It belongs to the Fabaceae, kin to the pea, the lentil, and the clover, and the genus name Trigonella ('little triangle') describes the three-cornered shape of its small pale flower. From one annual plant the cook takes three quite separate ingredients, which behave so differently that many cuisines treat them as unrelated: the hard, angular, ochre seed, bitter and aromatic, used whole or ground as a spice; the fresh green leaf, called methi across the Indian subcontinent, cooked as a slightly bitter leaf vegetable in the manner of spinach; and the dried leaf, the kasuri methi of the North Indian kitchen, crumbled at the last moment over a finished dish as an aromatic herb. No other plant in this atlas divides itself so completely between the spice rack, the herb jar, and the vegetable basket.

Common fenugreek, Trigonella foenum-graecum, was domesticated in the Fertile Crescent of the Near East, and it is among the oldest cultivated plants for which we have direct evidence: charred seeds recovered from Tell Halal in Iraq have been dated to around 4000 BCE, and further finds from Bronze Age Lachish and from the Neolithic levels of the Levant confirm a plant taken into cultivation alongside the earliest wheats, barleys, and pulses. Its earliest uses were not culinary alone. Fenugreek was fodder, medicine, and embalming spice together: the Latin foenum graecum, 'Greek hay', records its long career as a fragrant forage crop, and seeds were found in the tomb of Tutankhamun, whilst the Egyptian Ebers Papyrus of about 1550 BCE prescribes it for burns and for easing childbirth. The seed's peculiar aroma, at once sweet and savoury and unmistakably reminiscent of maple syrup or burnt sugar, comes from a single powerful compound, sotolon, which is so potent that it is detectable at a few parts per billion and which passes into the sweat and milk of those who eat the seed in quantity.

A second and quite distinct species must be set beside it. Blue fenugreek, Trigonella caerulea, is a separate plant of the South Caucasus and the uplands of the eastern Mediterranean, taller and softer than its cousin, and it is not the seed but the whole dried and powdered flowering top that is used. Its flavour is gentler, greener, and less bitter than that of the common seed, and it is indispensable in two kitchens that could hardly be further apart: in Georgia, where it is called utskho suneli ('the spice from afar') and forms the backbone of the khmeli suneli blend and of every walnut sauce in the national repertoire, and in the Swiss canton of Glarus, where it has flavoured the hard green herb cheese Schabziger since the Middle Ages. Because the two species are used in wholly different ways and in wholly separate culinary worlds, they are shown here as two origins and two journeys.

Fenugreek travelled early, quietly, and very far, and the routes it took were those of medicine and fodder as much as of the kitchen. From its Fertile Crescent homeland the common fenugreek spread in every direction along the oldest agricultural corridors of the Old World. It reached the Nile Valley by the second millennium BCE, where the Egyptians made it a plant of medicine, of the embalmer's workshop, and of the household drink helba, a golden infusion of the boiled seed that Egyptians still take today against a cold and, sweetened, as a winter comfort. It passed westward to Greece and Rome, though more as forage than as flavour: Cato the Elder set out how to sow it for cattle, and the Latin name it earned there, foenum graecum or 'Greek hay', is the name almost every European language still uses, the English 'fenugreek' among them.

Eastward the plant found the kitchens that would make the most of it. It reached the Indian subcontinent in antiquity, named methika in the Sanskrit medical texts and folded into the Ayurvedic pharmacopoeia long before it became a daily flavouring, and India took the plant more completely than anywhere else on earth, learning to use all three of its parts. In the North the seed entered the pickle and the tempering pan and the dried leaf became the crumbled finishing herb of the rich Punjabi gravies; in the West, in Gujarat and Rajasthan, the fresh leaf became a true vegetable, kneaded into flatbreads and fried into fritters, and the town of Kasur gave its name to the dried leaf that the whole subcontinent calls kasuri methi. In the Dravidian South the seed took on a different and stranger role altogether: a pinch of it, ground into the soaked rice and lentils of a dosa or idli batter, both feeds and shapes the overnight fermentation and lends the finished pancake its golden colour and its crispness, an act of practical microbiology performed in South Indian kitchens for well over a thousand years.

South and west, the plant crossed into Arabia along the caravan routes, and in the highlands of Yemen it became something close to a national obsession: hulba, the seed soaked, ground, and whipped with water into a pale, bitter, airy froth, is spooned over the bubbling stew saltah and the wheaten porridge aseed, and no Yemeni table is complete without it. From Yemen it crossed the narrow Red Sea to the Horn of Africa, where Ethiopia knows it as abish and grinds it into berbere, stirs it through the wat, and drinks it as a tonic. Northward it entered Anatolia, where the Ottoman and Armenian butchers of Kayseri bound it with garlic and red pepper into çemen, the thick reddish-brown paste that is caked around air-dried beef to make pastırma, and thence into the Balkans. Blue fenugreek, meanwhile, made a shorter and quite separate journey of its own: from the South Caucasus, where Georgia built an entire national seasoning upon it, the plant was carried into the alpine meadows of Central Europe, and by the fifteenth century the monks and dairymen of Glarus in Switzerland were grinding its dried flowering tops into skimmed-milk curd to make the pungent green cheese Schabziger, a use found nowhere else in Western Europe.

India today grows the overwhelming majority of the world's fenugreek, and the states of Rajasthan, Gujarat, and Madhya Pradesh account for most of that harvest; the remainder comes chiefly from Egypt, Turkey, Ethiopia, Iran, Morocco, and Nepal. The plant's three products move in separate trades. The seed is exported as a spice and, increasingly, as an industrial raw material, for its sotolon is the cheapest convincing source of a maple aroma, and imitation maple syrup, along with a good deal of commercial curry powder, owes its smell to fenugreek; the seed's steroidal saponin diosgenin, meanwhile, is a feedstock for the pharmaceutical synthesis of steroid hormones. The fresh leaf is a market vegetable across the subcontinent, and the dried leaf, kasuri methi, travels the world in small foil packets to the diaspora kitchens that cannot do without it.

In the kitchen the three forms remain stubbornly distinct. The whole seed is bitter and must be tamed: it is bloomed briefly in hot oil in a South Indian tempering, cracked into a mango pickle, sprouted, or soaked overnight and ground to a paste, and it turns acrid and inedible if it is allowed to scorch, a fault that ruins more curries than any other. The fresh leaf is cooked as a green, its faint bitterness the point rather than the problem, most famously with potato as aloo methi. The dried leaf is crushed between the palms over a finished dish, never cooked at length, and it is this last gesture that gives the butter chicken and the makhani gravies of North India the aroma by which they are instantly known. Beyond the spice rack the seed has one of the oldest and most persistent medicinal reputations of any plant: it is taken across the Near East, North Africa, and South Asia as a galactagogue to promote the milk of nursing mothers, a use recorded in the Ebers Papyrus three and a half thousand years ago and still current in every one of those regions today.

Blue fenugreek keeps its own separate modern life. In Georgia the ground herb, utskho suneli, is the single most characteristic seasoning of the national cuisine, essential to khmeli suneli and to the walnut sauces (satsivi, bazhe, and the walnut pastes of pkhali and badrijani) that define the Georgian table; it is not interchangeable with common fenugreek, and Georgian cooks are emphatic on the point. In Switzerland the same plant, grown in the Glarus valleys, is still ground into Schabziger, the rock-hard, pale-green, intensely pungent cheese that is grated over pasta and potatoes or beaten with butter into a spread, and which holds a protected designation of origin. That one modest legume of the Near East should underpin the aroma of a Punjabi curry, a Yemeni breakfast, an Ethiopian stew, a Turkish cured beef, a Georgian walnut sauce, and a Swiss alpine cheese is a fair measure of how far and how quietly fenugreek has travelled.