Summary:
Lactarius controversus is one of several large Lactarius species with white unchanging milk and very peppery taste. It is distinguished by a viscid appressed-fibrillose cap, pinkish-tinted gills, and its association with aspen, poplar and willow. Hesler(4) gave the distinctive features as a white, matted-fibrillose to bald cap that is often stained pinkish to lavender or brownish, slowly but strongly burning-acrid milk, small spores, and narrow pleurocystidia and cheilocystidia.

Cap:
(4)7-16(22)cm across, large, convex to sunken to funnel-shaped, margin inrolled at first; white or whitish, sometimes with stains that are "lavender, smoky lavender, lavender-brown, or vinaceous to pink", usually with narrow zones in marginal area; appressed-fibrillose, viscid but soon dry, margin short pubescent-tomentose at first, (Hesler), 5-15cm across, convex to uplifted, margin inrolled to incurved; azonate, white to off-white, "at times with pink, vinaceous or lavender-brown stains"; "appressed-fibrillose, subviscid to viscid", margin short-tomentose to pubescent, (Methven)

Flesh:
firm; white, (Hesler), up to 1.5cm thick at disc; white, unstaining on exposure, (Methven), MILK white, unchanging, not staining, slowly peppery, (Hesler), white, unchanging, unstaining, (Methven)

Gills:
adnate to subdecurrent, close to crowded, narrow, some forking near stem; pale pink to "light vinaceous-fawn", becoming pinkish cream when old, (Hesler), "adnate to subdecurrent, close to crowded, narrow", forking near stem; "initially pale pink, pink, or pinkish cream", unstaining where cut, edges colored as faces, (Methven)

Stem:
2.5-5(8)cm x 1.6-2.5(5)cm, equal or narrowing downward, stuffed then hollow, sometimes off-center; white; somewhat tacky when wet, sometimes spotted, (Hesler), 3-7cm x 1.5-2.5cm, round in cross-section, equal or narrowing toward base, hollow; white; dry or tacky to touch, bald to pruinose, not scrobiculate, (Methven)

Odor:
mild to slight and pleasant (Hesler), not distinctive (Methven)

Taste:
slowly but strongly burning-peppery (Hesler), slowly burning-peppery (Methven)

Microscopic spores:
spores 6-7.5 x 4.5-5 microns from sections, elliptic, ornamentation "a broken to partial reticulum with many free ends, some isolated particles and warts present", prominences 0.2-0.5 microns high; basidia 4-spored, +/- 37 x 7.5 microns; pleurocystidia of the intermediate type (30-45 x 3-5 microns), "aciculate and with one or more subapical constrictions, often buried in the hymenium"; cheilocystidia +/- basidiole-like; cap cuticle "a distinct ixocutis of collapsing hyphae mostly thin-walled", (Hesler), spores 6-7.5 x 4.5-5.5 microns, elliptic, amyloid ornamentation a broken to partial reticulum up to 0.5 microns high; basidia 35-45 x 7.5-9 microns; macrocystidia 30-45 x 4.5-6 microns, aciculate, often with one or more subapical constrictions, cheilocystidia absent; cap cuticle an ixocutis; stem cuticle "a simple cutis with scattered, projecting hyphal tips", (Methven)

Spore deposit:
cream to "pale pinkish-cinnamon" [Ridgway(1) color], (Hesler), pale yellow in mass (Methven), pink-cream (Buczacki)

Notes:
Material cited from OR, ID, ON, AK, CO, ME, MI, NM, WY, Netherlands, and the United Kingdom, (Hesler(4)). It is included by Methven(2) for CA and Cripps for MT. There is a collection from BC at the Pacific Forestry Centre. There are also collections from BC and AB at the University of British Columbia. There are collections from WA, AK, CO, MI, and WY at the University of Washington.

EDIBILITY

not recommended (Arora, Lincoff(1))