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Danny’s DNA Discoveries – Lactarius of the PNW
by Danny Miller

Click here for my Pictorial Key to Lactarius


Read my introduction to Russula for an explanation of what makes Russula and Lactarius unique among gilled mushrooms. Lactarius are notable for bleeding a latex, often called a milk, when broken, especially from the gills. The milk is usually white, but may be yellow, orange or red (or rarely blue!) and even change colours while you watch. They look somewhat like Russulas, but unfortunately, there's a lot more variety of statures, so you can't as easily learn to recognize a Lactarius on sight as you can a Russula - you may need to break it to see the latex (which may be scanty or, if the mushroom has dried out, even lacking). Not every "bleeding" mushroom is a Lactarius, though. The most common other "bleeders" are much smaller and more delicate Mycenas. Even small Lactarius are not very delicate (although they are fragile, as explained under Russula).

Some common features of Lactarius that might help you spot one are a frequently zoned cap, scrobiculate stem (covered with large, round pits of pigment), and a inrolled cap margin that might be bearded with hairs. Some species don't have any of these features, though. It's very common for them to taste acrid, or somewhat hot like a hot pepper, just like some Russulas. Not many other mushrooms besides Russula and Lactarius have that taste.

Normally there is a subgenus/clade named after the genus, so there "has been/should be/will be again" a clade "Lactarius", but right now, the species that have been placed in clade "Lactarius" are not actually related to each other, so some fixing and shuffling of species will have to be done before that clade name can be properly used.

abundant common uncommon rare - colour codes match my Pictorial Key and are my opinions and probably reflect my bias of living in W WA. Rare species may be locally common in certain places at certain times.

Deliciosi Clade - Coloured Milk - click to expand

This clade has coloured milk, instead of the whitish milk that every other Lactarius will have (although the white milk in other clades might turn yellow in a matter of seconds or eventually stain tissue purple). Usually you'll find orange or red latex, and the mushrooms themselves are usually orange or red too, often with a beautiful, prominent green staining. The east coast has a common blue Lactarius that bleeds blue milk and I'm very jealous. Most of them taste rather mild, or at most slightly bitter or slightly hot.

Species mentioned: Lactarius deliciosus, deliciosus var. areolatus, deliciosus var. olivaceosordidus, deliciosus var. piceus, aurantiosordidus, deterrimus, aestivus, rubrilacteus, barrowsii

Russularia Clade - Candy Cap relatives - click to expand

Candy caps are species of Lactarius that smell and taste like maple syrup when dried. They make excellent desserts, something unusual for a mushroom. To eliminate the more typical mushroom flavours from the food, the mushrooms are powdered and mixed into a fat - like cream or butter and used to make ice cream or popcorn or cookies. Unfortunately they are hard to identify because they do not smell or taste that way when fresh (some people use a lighter to burn them to see if they can coax a sweet smell out of them in the field for identification purposes). There also exists an Oregon candy cap "truffle" in this clade.

Mushrooms in this clade are usually small, with caps about 5 cm wide and stems <1 cm thick, but there are exceptions. They are usually orange-brown to red-brown and bleed a white milk. They are mostly mild or only slightly hot tasting (with one notable exception). (A few small brown or greyish-brown Lactarius that are not in this clade either have a velvety cap or are very slimy all over).

Species mentioned: Lactarius rubidus, fragilis, camphoratus, subviscidus, substriatus, subflammeus, aurantiacus, luculentus var. luculentus, luculentus var. laetus, tabidus, theiogalus, thejogalus, alpinus var. alpinus, alpinus var. mitis, cuspidoaurantiacus, occidentalis, carbonicola, lepidotus, rufus, atrobadius, badiosanguineus, hepaticus, xanthogalactus, chrysorheus, vinaceorufescens

Plinthogalus Clade - Lactarius fallax group - click to expand

Members of this subgenus have velvety caps. The most common and obvious ones are very velvety dark brown mushrooms. Rarely, we find a minutely velvety pale capped mushroom in this subgenus.

Species mentioned: Lactarius fallax, fallax var. concolor, pallidiolivaceus, fumosus var. occidentalis

Piperites Clade - everything else

This is the largest clade, so I will break them up into smaller groups. Most of them are at least somewhat peppery tasting (and most peppery species are in this clade).

Milk that turns yellow - click to expand

Within 10 seconds or so, the milk of these species will turn from white to yellow before your eyes, as shown above.

Species mentioned: Lactarius scrobiculatus var. canadensis, olivinus, scrobiculatus var. montanus, leonis, tuomikoskii, alnicola, payettensis, resimus, resimus var. regalis, resimus var. intermedius, aquizonatus, auriolla, xanthogalactus

Purple staining Lactarius - click to expand

This reaction may take a few minutes, but the milk will stain the mushroom's own tissues purple. The milk itself doesn't turn purple, nor will the milk turn anything purple except other parts of itself. Most, except for L. representaneous and L. cascadensis appear to form a clade of related species. The other two are of unclear affiliation.

Species mentioned: Lactarius pallescens, californiensis, montanus, uvidus, cascadensis, cordovaensis, aspideus, aspideoides, salicis-reticulatae, flavopalustris, flavoaspideus, salicis-herbaceae, pallidomarginatus, representaneus

Other Lactarius - click to expand

Species mentioned: Lactarius glyciosmus, pseudomucidus, controversus, pseudodeceptivus, argillaceifolius var. megacarpus, kauffmanii, kauffmanii var. sitchensis, mucidus, caespitosus, glutigriseus, affinis, trivialis, flexuosus, pseudoflexuosus, circellatus var. borealis, rufus, hysginus, hysginus var. americanus, necator, turpis, olivaceoumbrinus, sordidus, pubescens var. betulae, scoticus, torminosus var. nordmanensis, subvillosus, pseudodelicatus, sanmiguelensis, olympianus, zonarioides, vietus


This is a separate genus now, of mainly tropical species. We don't have any confirmed species in the PNW, although the European Lactifluus volemus has been rumoured from far northern Alberta and BC. It is big and orange with a dry, minutely velvety cap and a fishy odor.

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