Summary:
This species and its close relatives are recognized by overall dingy greenish to murky olive-brown color and copious white peppery milk. Other features of Lactarius olivaceoumbrinus include large size, a viscid cap that may be zonate and has a pubescent margin, milk that may eventually turn greenish gray, a scrobiculate stem, and growth under conifers.

Cap:
3-12cm across, convex with inrolled margin becoming flat or shallowly depressed; "typically a mixture of dark olive, sordid olive-brown, and olive-buff, often spotted or zonate concentrically", but zones fading when old; viscid when moist, (Arora), (2)4-10(12)cm across, convex with inrolled margin, expanding to flat or shallowly depressed; '"dark olive" on disc and deep olive toward the "dark olive-buff" margin, at times with green and "Isabella color" alternating zones, in age fading and nearly azonate, drying dark fuscous olive'; viscid, bald except pubescent margin, (Hesler), 8-15cm across, convex to flat, disc depressed, margin inrolled to incurved; olive brown to brown, zoned to obscurely zoned; fibrillose to fibrillose-scaly, subviscid to viscid, often water-spotted, margin pubescent to short-tomentose, (Methven)

Flesh:
thick, brittle; dingy olive, (Arora), thick, firm; pallid olivaceous, in stem changing to dingy gray, (Hesler), up to 1cm thick at disc, pale tan, unstaining on exposure, (Methven), MILK copious; white, turning greenish gray (sometimes very slowly), (Arora), copious; white, rapidly or slowly changing to greenish gray, (Hesler), white, unchanging, staining the gills olive brown where cut, (Methven)

Gills:
adnate to decurrent, crowded; "pallid becoming spotted or colored greenish or olive-gray", (Arora), decurrent, crowded, narrow, many forking near stem; "pallid at first, becoming greenish then spotted dingy olive-gray", finally olive-gray overall; edges even, (Hesler), "subdecurrent, close to crowded, broad", forking near stem; pale orange, staining olive-brown where cut, finally brown overall; not marginate, (Methven)

Stem:
4-8cm x 1-3cm, solid becoming hollow when old, rigid; more or less cap-colored; viscid when wet, then dry; usually scrobiculate, (Arora), (1.5)4-8(10)cm x (0.8)1-1.5cm, widening downward, occasionally narrowed in lower part, solid but hollow when old; more or less cap-colored; viscid, soon dry, bald, scrobiculate, (Hesler), 4-7cm x 0.8-1.5cm, round in cross-section, hollow, equal or narrowed toward base; olive-brown to brown; bald, "moist to subviscid, fibrillose-streaked", scrobiculate (scrobiculae darker), (Methven)

Veil:
[none]

Odor:
not distinctive (Methven)

Taste:
very peppery (Arora), mild intensely peppery, "leaving a burning sensation afterward", (Hesler), slowly peppery (Methven)

Microscopic spores:
spores 7-10 x 6-9 microns, elliptic to nearly round, amyloid warts and ridges, (Arora), spores 7-9(10) x 6-8(9) microns, elliptic to nearly round, "broken to partial reticulum with bands frequently with free-ending branches, some isolated particles and warts present", prominences 0.4-1(1.5) microns high; basidia 4-spored, 45-57 x 8-11 microns; pleurocystidia: macrocystidia 45-75 x 5-10 microns, "fusoid, acute to acuminate, often with somewhat granular content, more numerous near the gill edges", "pseudocystidia scattered, content refractive, filamentous, embedded in the hymenium and inconspicuous", cheilocystidia 37-60 x 4.5-7 microns, "fusoid-acuminate, some with one or more subapical constrictions", (Hesler), spores 7-9(9.5) x 6-8 microns, broadly elliptic to elliptic, amyloid ornamentation a broken to partial reticulum 0.5-1.5 microns high; basidia 40-55 x 7-10.5 microns; macrocystidia 40-70(90) x 4.5-7.5 microns, fusoid to acuminate, often with one or more subapical constrictions, cheilocystidia 35-55 x 4.5-7.5 microns, fusoid to acuminate with one or more subapical constrictions; cap cuticle "an ixocutis, producing a diffuse magenta pigment in KOH"; stem cuticle "an ixocutis, producing a diffuse magenta pigment in KOH", (Methven)

Spore deposit:
pale buff (Arora), "light buff" (Hesler), white to pale yellow (Methven)

Notes:
Hesler(4) cited collections from WA, OR, and ID. Methven(2) gives it for CA and Miller(14) for AK. There are collections from BC at Pacific Forestry Centre and the University of British Columbia.

EDIBILITY

unknown (Arora)