Sweet Woodruff: The Woodland Plant That Smells of Hay

Sweet woodruff has no scent worth noticing when fresh. Walk past a clump in May, even with your nose down at leaf level, and you would not pick it out from the other woodland green. Pick a handful and dry it for an afternoon, and the smell that develops is so specific it is unmistakable: hay and vanilla and a faint hint of almond, the smell of a Devon farmhouse kitchen in summer. The compound responsible is coumarin, locked in the leaf until the plant begins to wilt, and the German May custom of Maibowle is built around the brief window between the two.

Identifying

Galium odoratum grows in deep shade under hawthorn, beech, and oak, where little else carpets the ground in May. The leaves are narrow, lanceolate, and arranged in whorls of six to eight around the stem, like the spokes of a tiny wheel. The flowers are small, white, and four-petalled, held in a loose cluster just above the topmost whorl. The plant rarely grows above twenty centimetres and spreads by underground rhizomes, forming dense low patches across the woodland floor. It is in flower for about three weeks from early May.

The coumarin chemistry

Coumarin is the compound that gives freshly cut hay its smell. It is present in many grass-family and several other plant species, locked inside the leaf as a glycoside that does not release its scent until the leaf is damaged. As the leaves of sweet woodruff begin to wilt, the cell walls break down and the coumarin volatilises, releasing the characteristic sweet hay smell. Fully dry leaves smell stronger than partly wilted ones. The smell can persist for years if the dried leaves are kept in an airtight container; sweet woodruff was packed into mattresses and stored linen exactly for this reason.

The strewing tradition

Sweet woodruff was strewn on the floors of churches, halls, and parlours in spring and summer, and packed into mattresses for the smell. Dorothy Hartley, writing in Food in England (1954), records the use of woodruff in English country houses well into the nineteenth century as an infusion to flavour wines, and as a strewing herb on the church floor at Whitsun. By her time it was a memory in most households, long displaced by lavender and rose. The plant itself is still common in old woodland and ancient hedge bottoms across England, and Hertfordshire is well off for it.

Maibowle: the German May punch

In Germany, the Alsace, and across the Rhine valley, sweet woodruff has a specific May role: it is the central ingredient in Maibowle (sometimes Waldmeisterbowle), a chilled white wine punch made by steeping the wilted leaves in light Riesling or Sylvaner for an hour or two before serving with strawberries floating on top. The drink is associated with the first of May and with weddings, and survives not because anyone has insisted on it but because the drink is genuinely good. The fresh-cut-hay flavour of the wilted woodruff is unlike anything else you can put in a glass of wine.

The safety note

A point worth knowing about coumarin: the compound is harmless in small quantities, but in larger doses it acts as an anticoagulant and is toxic to the liver. Aged or overdried woodruff concentrates the coumarin and is best avoided. The German food regulation limits Maibowle to freshly wilted leaves only and to a brief steep, no more than two hours in the wine. Treat it as a seasonal drink, not a daily one. Used the traditional way, in small glasses on a May evening, it has been served safely for a thousand years.

Sources: Dorothy Hartley, Food in England (1954); RHS species note: Galium odoratum; Bundesinstitut für Risikobewertung (German Federal Institute for Risk Assessment) guidance on coumarin in foodstuffs.