Summary:
Subgenus Russularia. Lactarius subflammeus may be the same species as Lactarius substriatus. These two and others including Lactarius luculentus that have traditionally passed under the name Lactarius aurantiacus are typified by an orange, viscid cap, a stem usually longer than the width of the cap, and white unchanging milk. Lactarius subflammeus is said to have a bright orange to reddish brown, moist to viscid cap, white unchanging milk, a slightly peppery taste, a white spore deposit, and a cap cuticle that is a modified ixotrichoderm with irregularly inflated cells not forming a cellular layer. Barge(1) produced a molecular phylogeny in which the holotype of Lactarius subflammeus falls within a clade of collections identified as Lactarius substriatus and conclude that the two taxa "may be conspecific". They go on to say, with species names italicized, "Molecular phylogenetic analyses ... suggest that L. subflammeus is conspecific with L. substriatus; however, sequencing of the holotype of L. substriatus is needed to confirm this observation."

Cap:
3-7cm across, convex becoming shallowly depressed with margin +/- arched; 'scarlet when young but very soon orange ("xanthine orange")' becoming duller when old; slimy-viscid, bald, naked, "margin with short translucent striations at maturity", (Hesler), 2-6(7)cm across, convex becoming flat or shallowly depressed; 'scarlet when young soon fading to bright orange and eventually dull orange', not zoned; smooth, viscid, margin naked, (Arora), (1)2-5cm across, convex to flat, disc depressed, margin incurved to downcurved; brownish red to reddish brown, darkest on disc, margin paler; moist to subviscid, bald, not zoned, margin translucent-striate, (Methven)

Flesh:
thin, fragile; 'watery pinkish buff to dull orange-buff', (Hesler), thin, fragile, (Arora), 0.2-0.5cm thick at disc; light orange in cap and stem, not staining with exposure, (Methven), MILK milk-white, unchanging and not staining, (Hesler), white, unchanging, (Arora), white, unchanging and unstaining, (Methven)

Gills:
"broadly adnate to decurrent, close to (finally) subdistant, moderately broad"; ''whitish ("pale pinkish buff") coloring +/- evenly overall to +/- concolorous with cap'', (Hesler), "adnate to decurrent, fairly close"; "whitish or colored like cap but paler", (Arora), adnate to subdecurrent, close to subdistant, narrow, rarely forking near stem; pale orange, not staining where cut, edges colored as faces, (Methven)

Stem:
4-9cm x 0.8-1.5cm at top, widened downward, hollow, fragile; hoary at first, soon naked and colored as mature cap; "not viscid, surface often uneven", (Hesler), 4-9cm x 0.5-1.5cm, usually rather long and wider toward the base, "hollow, rigid but fragile"; colored like cap; not viscid, (Arora), 2-6cm x 0.3-1cm, equal or widening downward, round in cross-section, hollow; brownish orange to light brown; dry to moist, bald, white to pale orange tomentum at base, (Methven)

Odor:
slight (Hesler), mild (Arora), not distinctive (Methven)

Taste:
peppery (Hesler), slowly peppery, (Arora), slowly, slightly peppery (Methven)

Microscopic spores:
spores 7.5-9 x 6.5-7.5 microns, elliptic, [amyloid] ornamentation of short ridges and warts not forming a reticulum, prominences 0.5-1.0 microns high; basidia 4-spored, about 42 x 9 microns; pleurocystidia: macrocystidia 52-93 x 6-10 microns, fusoid-ventricose to subcylindric, tapered to an acute apex when old, conspicuously projecting, pseudocystidia filamentous; cheilocystidia 37-45 x 4-6 microns, otherwise similar to pleurocystidia; gill trama of interwoven hyphae (in sections often "cellular" in appearance); cap trama heteromerous (but with random associations of sphaerocysts rather than typical rosettes); cap cuticle "a modified ixotrichoderm, the elements with somewhat enlarged cells at the base of the turf-element, orientation of elements upright to decumbent, slime evident in KOH mounts"; stem cuticle "a compact zone of narrow vertical hyphae with occasional caulocystidia" (not embedded in slime), (Hesler), spores 7.5-9 x 6.5-7.5 microns, elliptic, with amyloid warts and ridges, (Arora), spores 7-9 x (5.5)6-7 microns, broadly elliptic to elliptic, amyloid ornamentation a broken reticulum 0.5-1.0 microns high; basidia 30-45 x 6-9 microns; cheilocystidia 35-50 x 4.5-7.5 microns, subcylindric to fusoid-ventricose, often with one or more subapical constrictions, macrocystidia 50-100 x 6-9 microns, fusoid-ventricose to subcylindric, at times with one or more subapical constrictions; cap cuticle a modified ixotrichoderm, elements arising from inflated basal cells that do not form a cellular layer; stem cuticle "a simple cutis with scattered projecting hyphal tips", (Methven)

Spore deposit:
white (Hesler, Methven), whitish (Arora)

Notes:
Lactarius subflammeus material was cited from WA, OR (including the holotype), ID, and CO, (Hesler(4) who say it is one of the very common species in the fall in the conifer forests of the Pacific Northwest). It has been found in CA (Methven), and there are collections from BC at the Pacific Forestry Centre and the University of British Columbia. The University of Washington has collections from WA and AK. The holotype is from OR.

EDIBILITY

unknown (Arora)