Summary:
Lactarius scrobiculatus group is recognized by the pale yellow to dark ocher color, scrobiculate stem, and white milk that quickly turns yellow and stains exposed tissues yellowish. |The common North American variety is Lactarius scrobiculatus var. canadensis which is characterized (Methven) by a viscid yellow cap with a densely bearded margin; at most a slightly peppery taste; light brown stains that develop on the gills and flesh overnight; a white to pale yellow spore deposit; and amyloid ornamentation that is at most a broken reticulum. |It differs from the type (European) variety in having (Hesler) white to cream-colored spore deposit (instead of ocher), scanty latex, only slightly peppery taste, and much less robust stature as a rule. |When Hesler(4) did their monograph they decided that Lactarius payettensis var. canadensis A.H. Sm. should be a variety of Lactarius scrobiculatus rather than a variety of L. payettensis. The online Species Fungorum, accessed June 30, 2020, nevertheless listed Lactarius scrobiculatus var. canadensis under L. payettensis, rather than under Lactarius scrobiculatus. MycoBank, accessed the same day, listed the two names for var. canadensis as obligate or heterotypic synonyms. |Methven described var. montanus (occurring at least in CA) which is distinguished from var. canadensis by the "pale yellow, subviscid pileus with a fibrillose margin that is soon glabrous, slightly acrid taste, lack of cheilocystidia, and semihypogeous habitat in montane coniferous forests", with amyloid ornamentation intermediate between var. canadensis and var. pubescens. |Var. pubescens is also a montane species but has a pale yellow cap, variable vestiture on the cap margin, smaller spores (6-7.5(8) x 5-6 microns) than both var. montanus (8-9.5 x 5.5-7 microns), and var. canadensis (7-9(9.5) x (5.5)6-7 microns) and amyloid ornamentation in the form of a broken to partial reticulum. |Siegel(2) name their entry Lactarius scrobiculatus group and call it a confusing species complex. They say that the common form of L. "scrobiculatus" found on the Far North Coast [of California] "can be told apart from similar milk caps by the yellowish, funnel-shaped cap, coarsely scrobiculate stipe, white latex, and strongly acrid taste. L. scrobiculatus var. canadensis is slightly smaller and paler capped and has white latex that quickly changes to yellow and a mild to slightly acrid taste", (Siegel(2) with Latin name italicized).

Cap:
4-15(20)cm across, convex to flat with center usually depressed, when old often vase-shaped, margin inrolled when young; pale yellow to yellowish to bright ocher, the center sometimes darker, unzoned or faintly zoned; viscid when moist, smooth or scaly when old, margin typically bearded with hairs (but hairs absent or inconspicuous in var. montanus and var. pubescens), (Arora), (3)4-10(12)cm across, convex to flat-depressed; "whitish becoming olive-buff and slowly yellow in aging, or soon dull yellow and drying dull ochraceous", or yellow from youth to maturity; "viscid at first but soon dry", +/- fibrillose and margin bearded at first or margin only pubescent, "near the margin the cuticle often broken into appressed squamules", margin often bald at maturity, (Hesler(4) for var. canadensis)

Flesh:
thick, firm, brittle; whitish but staining yellow when exposed, (Arora), "firm, brittle becoming lax"; white, (Hesler(4) for var. canadensis), quickly becoming yellow when exposed (Methven for all three California varieties), MILK scanty (but copious in type variety from Europe), white, quickly turning sulphur-yellow when exposed, (Hesler(4) for var. canadensis), white, quickly turning yellow when exposed, (Methven for all three California varieties)

Gills:
adnate to slightly decurrent, close; "whitish to pale or dull yellow", (Arora), short decurrent, crowded, narrow to moderately broad, equal in width, many forked once near stem, 2-3 tiers of subgills; whitish becoming ochroleucous [pale ocher], staining yellowish and finally at times +/- clay color where injured, (Hesler(4) for var. canadensis), "adnate to subdecurrent, close, narrow to broad", forked near stem; light yellow to pale orange, staining yellow to grayish brown where cut, (Methven for var. canadensis), "whitish with a faint yellow or pink tint", bruising pale pinky brown, (Phillips)

Stem:
3-11cm x (1)2-4(5)cm, "equal or narrowed at base, firm", hollow when old; white to yellowish; dry, "usually scrobiculate (i.e., pitted with large, glazed, darker or brighter yellow to honey-colored spots)", (Arora), 3-11cm x 1-3cm at top, +/- equal, stuffed becoming hollow; "surface usually with large glazed yellowish spots (scrobiculate), surface around them white to yellowish and unpolished, staining yellow and finally rusty brown where bruised", (Hesler(4) for var. canadensis)

Veil:
[none]

Odor:
faintly fragrant (Hesler for var. canadensis), not distinctive (Methven for all three California varieties), fruity (Phillips), fruity, sour, (Buczacki for Britain/Ireland)

Taste:
mild or finally slightly peppery (This is var. canadensis - var. scrobiculatus has very peppery taste in Europe but has not definitely been confirmed in North America.), (Hesler), not distinctive to slightly peppery for var. canadensis and var. montana, not distinctive to slowly, slightly peppery for var. pubescens, (Methven)

Microscopic spores:
spores 6-10 x 5-7.5 microns, broadly elliptic, with amyloid warts and ridges, (Arora), spores 7-9 x 5.5-7 microns, elliptic, "ornamentation in the form of branched ridges forming at most a broken reticulum, isolated elements frequent", prominences about 0.5 microns high; basidia 4-spored, 42-48 x 8-10 microns; pleurocystidia: macrocystidia 52-78 x 6-12 microns, projecting 5-20 microns beyond the hymenium, "fusoid, acute or some with one or more subapical constrictions", "many with spangled content as revived in KOH", pseudocystidia scattered, filamentous; cheilocystidia 37-45 x 6-8 microns, similar in shape to macrocystidia, (Hesler(4) for var. canadensis)

Spore deposit:
whitish to creamy or yellowish (Arora), white to cream (Crawshay A-B) for var. canadensis, but bright ocher (Crawshay D-E) in European type, (Hesler), white to pale yellow for var. canadensis and var. pubescens, pale yellow for var. montanus, (Methven)

Notes:
Lactarius scrobiculatus has been reported from BC (see Redhead(5)), and was cited by Hesler(4) from WA, OR, ID, NS, QC, AK, CA, CO, MI, (var. canadensis), and MI and QC (var. pubescens). Methven lists var. canadensis, var. pubescens, and var. montanus from CA.

EDIBILITY

not recommended (Arora)