Lactarius, Lactarius vietus, Lactarius glyciosmus, Lactarius violascens, Lactarius pyrogalus
Lactarius uvidus is a European and North American "milk-cap" mushroom, of which the milk turns violet when the flesh is damaged. The fungi generally identified as L. uvidus are part of a complex of closely related species and varieties which are difficult to delimit definitively, .
This cluster of species is found in deciduous and coniferous woods, with a preference towards acid soils. It has a wide distribution in Europe, North Africa, and North America, being fairly common in some regions but rare in others. It appears classified as vulnerable or endangered in the Danish and Dutch Red Lists of Fungi.
Lactarius uvidus belongs to section Uvidi of the genus, the members of which are characterized by milk which discolours violet, and by the greasy cap surface. These mushrooms are divided into two sub-sections: the Aspidieni, which have a whitish, ochre or greyish cap, and the Uvidini (including L. uvidus), which have a lilac, violaceous, or brownish cap. A more complete list of these species can be found in the List of Lactarius species.
Some less well-known but closely related European species are L. pseudouvidus Kühner (1985) (found in alpine zone, up to 4 cm in diameter, with ochraceous yellow gills), L. robertianus Bon (1985) (also alpine, darker coloured, with smell of cedar wood), and L. luridus (Pers.) Gray (1821) (whose milk goes a deep violet). Since L. uvidus seems to be a cluster of species, it is particularly difficult to pin down the correspondence between descriptions and collections originating from Europe (on one hand) and from North America (on the other).
Some examples of varieties inside the main species are L. uvidus var. pallidus Bres. (which is whitish), and L. uvidus var. candidulus Neuh. (which is small and pale and comes in muddy places).