Lactarius helvus

Lactarius helvus is a member of the large milk-cap genus Lactarius in the order Russulales. Fruiting bodies can be found in Sphagnum moss in coniferous and deciduous woodland in Europe. Mushrooms are pale brown-grey or beige in colour and funnel-shaped, with colourless watery milk. There is a distinctive smell which has been likened to fenugreek, celery, liquorice, or Maggi instant soup. Mildly toxic when raw, it has been implicated in the poisoning of 418 people near Leipzig in October 1949. However, it is used in small quantities as a spice when dried. Sotolon, the agent that gives the fungus its odour, also occurs in fenugreek, maple syrup and lovage.

Taxonomy

It was initially described by Elias Magnus Fries in 1821 as Agaricus helvus, before he placed it in the genus Lactarius in 1838. Peck's Lactarius aquifluus has been deemed a synonym. The specific epithet helvus is derived from the Latin for 'honey-yellow'. Its name in German is Maggipilz.

Description

The velvety cap is initially slightly convex (planoconvex), becoming funnel-shaped (infundibuliform) as it matures; it is 4-15 cm (1½-4 in) in diameter and has a faint zonate (bull's-eye) pattern, beige or light grey at the margins and darkening toward the centre. The decurrent gills are cream when young, and darkening to ochre-yellow with age. The flesh is white or beige, often pink-tinged. The latex, or milk, is watery and colourless, unlike that of any other milk-cap. The hollow cylindrical stalk is 3-9 cm (1-3½ in) high by 1-2 cm (½ in) wide. It may be whitish when young, ochre or pink-tinged, and sometimes spotted orange-brown. The highly distinctive smell has been described as reminiscent of fenugreek, with a mild taste. To others, the smell has been likened to lovage or celery, or liquorice or a packet of Maggi instant soup.

Distribution and habitat

Fruiting bodies are found in groups in woodlands near conifers such as Picea and Pinus, as well as the deciduous birch (Betula) and rarely beech (Fagus). More specifically, they occur in wet places, often growing in Sphagnum, in late summer and autumn. The species is found across Europe and Asia.

Toxicity

The symptoms occur within thirty minutes of consumption, with nausea and vomiting accompanied by vertigo and chills. The toxic agents are thought to be sesquiterpenes. In October 1949, 418 people were poisoned near Leipzig in eastern Germany. The toxins are destroyed by thorough boiling, and L. helvus is used in small quantities as a spice after drying.

The agent which gives the fungus its distinctive odour is sotolon, which also gives fenugreek seed and lovage their characteristic smells. It is present as well in molasses, aged sake and white wine, flor sherry, roasted tobacco, as well as in maple syrup.

References