Lactarius quietus

Lactarius quietus was first described and named by Swedish mycologist Elias Magnus Fries,[3] who named it Agaricus quietus in the first volume of his Systema Mycologicum, published in 1821.[4] In his later Epicrisis Systematis Mycologici, published in 1838, Fries transferred the species to Lactarius.[1] Subsequent attempts to reclassify the species were unsuccessful; in 1871, Paul Kummer described the species as a member of Galorrheus, and in 1891 Otto Kuntze classified it as Lactifluus, but today Fries's placement of the species in Lactarius is accepted.[1] The specific epithet quietus means "quiet" or "calm", and is possibly used to refer to the unintrusive colours of the cap.[5]

The variety Lactarius quietus var. unicolor was described by Fries in the second volume of his Monographia Hymenomycetum Sueciae, published in 1863.[6] The variety Lactarius quietus var. incanus was described by Lexemuel Ray Hesler and Alexander H. Smith in their 1979 North American species of Lactarius.[7] The name incanus translates as :hoary", referring to the whited bloom which can sometimes be seen on the mushrooms.[5]

Lactarius quietus is known by the common names oak milkcap,[8][9] oakbug milkcap[10][11] and the southern milkcap.[12] Lactarius quietus var. incanus is commonly known as the burnt sugar lactarius.[5]

L. quietus gills and milk

Lactarius quietus typically has a convex cap of 5 to 8 centimetres (2.0 to 3.1 in) across, which later flattens or develops a small depression in the centre. In colour, the cap is a dull reddish brown with a tint of cinnamon, sometimes with darker concentric bands or spots.[8] This zoning is one of the most distinctive features of the species.[13] The cap is dry and matt, and not sticky when moist. It features a thick layer of firm, whitish-buff flesh.[8] The stem measures from 4 to 9 centimetres (1.6 to 3.5 in) in height, and is typically 10 to 15 millimetres (0.39 to 0.59 in) thick. It is cylindrical in shape, but is sometimes furrowed lengthways,[8] and it lacks a ring.[9] It is concolorous with the cap, or a little darker, and is sometimes hollow.[8] The brownish-white gills are slightly decurrent, and change colour with age to a pale reddish brown with mauve hints. The milk is white or cream in colour.[8] The mushroom has a distinctive, strong oily smell,[13] which has also been likened to bedbugs and wet laundry.[11] The spores are oval, with plentiful warts joined by numerous ridges, forming a well-developed network. The spores typically measure 7.5 to 9 by 6.5 to 7.5 µm, and leave a cream print.[8]

Lactarius quietus has been variously described as edible[3][8] and inedible.[9][13] The milk has a mild or slightly bitter taste.[8] L. quietus var. incanus also has conflicting reports concerning its edibility, and so is not recommended.[5]

Lactarius quietus is found growing exclusively at the base of oak trees,[13] solitarily or in scattered groups, in soil.[9] It can be found very commonly throughout autumn months.[8] It is ectomycorrhizal, feeding symbiotically exclusively with oak,[14] though studies have suggested it is also able to feed saprotrophically, growing from organic soil matter.[15] L. quietus can be found only in Europe; in the United Kingdom, it is one of the one hundred most commonly encountered mushroom species.[11] L. quietus var. incanus is found commonly in eastern North America.[16]

• List of Lactarius species