text: lactarius alnicola lactarius alnicola , commonly known as the golden milkcap , is a species of fungus in the russulaceae family . the fruit bodies produced by the fungus are characterized by a sticky , vanilla - colored cap up to 20 cm ( 7 . 9 in ) wide with a mixture of yellow tones arranged in faint concentric bands . the stem is up to 5 cm ( 2 . 0 in ) long and has yellow - brown spots . when it is cut or injured , the mushroom oozes a white latex , which has an intensely peppery taste . the acrid taste of the fruit bodies renders them unpalatable . the fungus is found in the western united states and mexico , where it grows in mycorrhizal associations with various coniferous trees species , such as spruce , pine and fir , and deciduous species such as oak and alder . it has also been collected in india . two varieties have been named : var. , known from colorado , and var. pungens , from michigan . taxonomy the species was originally described by american mycologist alexander h. smith in 1960 , from a collection made near warm lake , idaho , two years prior . the species was originally collected under alders with conifers nearby , and its specific epithet reflects the presumed association between the species — alnicola means " living with alder " . researchers subsequently discovered that the species has a relationship with conifers , not with alders , as the name implies . the mushroom is commonly known as the " golden milkcap " . lactarius alnicola is classified in subsection of section piperites in the genus lactarius . species in this subsection are characterized by having a milk - white to creamy or whey - like latex that soon turns yellow upon exposure to air , and which may stain freshly cut surfaces of the fruit body yellow . further , the cap margin is bearded , strigose ( covered with sharp , straight , and stiff hairs ) , and coarsely tomentose or woolly when young . other species in the subsection include l. , l. , l. torminosus , l. payettensis , l. gossypinus , l. pubescens , l. and l. scrobiculatus ( the type species of the subsection ) . description the cap is 8 – 20 cm ( 3 . 1 – 7 . 9 in ) wide , initially convex but becoming depressed to funnel - shaped in maturity . the cap margin is initially rolled inward , then becomes uplifted as the cap expands . the cap surface is sticky to slimy , and near the margin there are matted " hairs " beneath the slimy or sticky layer . the color of the cap surface is yellow - ochre , sometimes with concentric bands of lighter and darker shades ; the color becomes paler near the margin . the gills are adnate ( squarely attached to the stem ) to decurrent ( attached to and running down the length of the stem ) , narrow , and crowded closely together . forked near the stem , the gills are initially whitish before becoming pale ochraceous - buff . there are many lamellulae — small gills that do not extend completely to the stem . the stem is 3 – 6 cm ( 1 . 2 – 2 . 4 in ) long and 2 – 3 cm ( 0 . 8 – 1 . 2 in ) thick , nearly equal in width throughout or tapered downward , dry , hard , coarsely pitted , and whitish to cream yellowish . it is initially solid , then becomes hollow with age . the flesh is thick , hard , whitish , and slowly stains pale yellow after the mushroom has been cut open . it has no distinctive odor , while the taste is immediately acrid . the latex is sparse , white on exposure to air , and unchanging or very slowly changing color to yellow . it stains cut flesh yellow , and tastes acrid . according to mycologist david arora , the oak - loving central and southern californian population of this species has a more latent acrid taste . the spore print may range slightly in color : thin deposits are white , thick deposits are more yellow . the mushroom is considered inedible because of the intensely peppery taste . microscopic characters the spores are 7 . 5 – 10 by 6 – 8 . 5 µm , ellipsoid , and ornamented with warts and narrow bands that form a partial reticulum . the surface prominences are up to 1 µm high , but mostly in the range 0 . 3 – 0 . 6 µm . the spores are hyaline ( translucent ) and amyloid , meaning that they will adsorb iodine when stained with melzer 's reagent . the basidia , the spore - bearing cells , are four - spored , and measure 37 – 48 by 8 – 11 µm . the cap cuticle is an ixocutis ( a tissue layer on the surface of a mushroom made of a layer of gelatinous hyphae ) made of encrusted hyphae that are 3 – 5 µm wide . varieties in their 1979 monograph of north american lactarius species , hesler and smith named two varieties of l. alnicola . lactarius alnicola var. , reported under mixed aspen and conifers from ashcroft , colorado , is very similar to the nominate variety , but it has a white to cream - colored cap and white , unchanging latex . it has slightly smaller fruit bodies , with caps up to 10 cm ( 3 . 9 in ) wide , and stems up to 4 cm ( 1 . 6 in ) long ; its spores are slightly larger , measuring 9 – 10 . 5 by 7 . 5 – 9 µm . lactarius alnicola var. pungens , reported only from mixed forests in michigan , is similar but has a tacky surface that soon dries , a dull ochraceous to ochraceous - tan cap with an ochraceous - tawny center . it has whitish flesh , with a pungent odor described as " distinct and peculiar " . similar species novice mushroom hunters may mistake l. alnicola for the edible species cantharellus cibarius , a choice edible species that has a vase - shaped fruit body with strongly decurrent gills . other similar lactarius species include l. zonarius , l. payettensis , l. , l. , and l. psammicola f. glaber . l. also associates with conifers , and has a pale yellow - ochre , frequently zonate cap , but may be distinguished by its stem , which is usually covered with spots . l. payettensis has a roughened , not smooth , cap margin . l. has a zonate cap and extremely acrid flesh . its gills change color from pale vinaceous to light pinkish - brown in maturity . l. psammicola f. glaber has a pinkish - buff spore print . mature fruit bodies of l. scrobiculatus var. montanus have been confused with l. alnicola . its fruit bodies feature a smooth cap margin , acrid taste , white latex which slowly ( over several minutes ) turns yellow on exposure or stains the flesh yellow , and do not turn " clay color " when bruised . ecology , habitat , and distribution lactarius alnicola is an ectomycorrhizal species , and engages in a mutualistic association with certain plant species . in this association , the hyphae of the fungus permeate large volumes of soil and obtain scarce elements , especially phosphorus — which is often limiting for plant growth — which they pass on to the plant in exchange for metabolic products of the plant 's photosynthesis . the ectomycorrhizae that the fungus forms in association with picea engelmannii have been shown to contain lactifers ( latex - producing cells ) and pigments similar to the fruit body . fruit bodies of the fungus grow in groups on the ground under alders and conifers , usually appearing between july and october . it is a fairly common species in the western united states and baja california . additional collection locations in mexico include veracruz , villarreal , and tapia . a population in central and southern california is known to associate with oak trees . in the rocky mountains it is associated with the subalpine tree species englemann spruce ( picea engelmannii ) , while at lower elevations it is commonly found with white spruce ( picea glauca ) . it is also known to associate with ponderosa pine ( pinus ponderosa ) and douglas - fir ( genus pseudotsuga ) . the mushroom has also been collected from , in the state of uttarakhand , india . cited books bessette ar , bessette a , harris dm ( 2009 ) . milk mushrooms of north america : a field guide to the genus lactarius . syracuse : syracuse university press . isbn 0 - 8156 - - 0 . hesler lr , smith ah ( 1979 ) . north american species of lactarius . michigan : the university of michigan press . isbn 0 - 472 - - 2 .