Lactarius tabidus Fr. - Birch Milkcap

Phylum: Basidiomycota - Class: Agaricomycetes - Order: Russulales - Family: Russulaceae

Lactarius tabidus, Birch Milkcap, Wales UK

Lactarius tabidus, the Birch Milkcap, is found in great abundance beneath birch trees in areas where the soil is damp, humus-rich and mossy. The white milk (latex) is sometimes rather sparse, especially in very young or old specimens and during prolonged dry weather.

Taste testing is an important step in identifying milkcap mushrooms, but for red-brown such as this it's best to taste only a little piece because some of its lookalikes produce extremely hot latex.

Lacvtarius tabidus, Hampshire, England

Distribution

Widespread and very common throughout Britain and Ireland, the Birch Milkcap is also found in most parts of mainland Europe. A very similar milkcap occurs in North America, reportedly mycorrhizal with pines; maybe one day DNA sequencing will show whether it is co-specific with the European species Lactarius tabidus.

Taxonomic history

The Birch Milkcap was described in 1838 by the Swedish mycologist Elias Magnus Fries, who established its scientific name as Lactarius rufus, which is still the binomial name by which it is generally referred to by mycologists today.

Synonyms of Lactarius tabidus include Lactarius subdulcis var. tabidus (Fr.) Quél., and Lactarius theiogalus.

Etymology

The generic name Lactarius means producing milk (lactating) - a reference to the milky latex that is exuded from the gills of milkcap fungi when they are cut or torn. The specific epithet tabidus is a Latin adjective that translates as 'stunted' - a reference to the small size of these milkcaps in comparison with many other members of the Lactarius genus.

Identification Guide

Cap of Lactarius tabidus

Cap

Convex at first, then flattening or becoming slightly funnel shaped, often with a shallow, narrow umbo; 2 to 4.5cm in diameter, the yellowish-brown to orange-brown caps, darkest towards the centre, are slightly hygrophanous and turn more ochre from the margin when old and dry.

Caps have finely matt and wrinkled surfaces, and old specimens are often visibly crenulate at the margin.

Gills of Lactarius tabidus

Gills

The gills, which are pale cinnamon with a pinkish tinge, are weakly decurrent and crowded. As they mature, the gills tend to become blotchy.

When the gills of this milkcap are damaged, a white latex is released; its taste is initially mild but later becomes acrid. On a white handkerchief or tissue the latex leaves a damp mark that slowly turns yellow.

Stem

Solid at first, eventually becoming hollow; 5 to 10mm in diameter and 3 to 7cm tall, the cylindrical or slightly upward-tapering stem is rather brittle; its surface is smooth and much the same colour as the cap, a little paler towards the apex and darker towards the base. The stem flesh is whitish; there is no stem ring.

Spores of Lactarius tabidus

Spores

Broadly ellipsoidal, 7-9 x 6-7μm, hyaline; ornamented with many pointed warts up to 1.2μm in height, mostly isolated but with just a few linking ridges.

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Spore print

Pale cream with a slight salmon pink tinge.

Odour/taste

No distinctive odour; initially a mild taste that gradually becomes more acrid.

Habitat & Ecological role

Ectomycorrhizal with hardwood trees, notably birches; in damp and often mossy woodlands.

Season

August to November in Britain and Ireland.

Similar species

Lactarius subdulcis is of similar coloration; it occurs mostly under beech trees.

Culinary Notes

The Birch Milkcap is generally considered to be inedible because of its acrid taste.

Reference Sources

Fascinated by Fungi, Pat O'Reilly, 2011

Funga Nordica, Henning Knudsen and Jan Vesterholt, 2008.

Fungi of Switzerland, volume 6: Russulaceae, Kränzlin, F.

BMS List of English Names for Fungi.

Dictionary of the Fungi; Paul M. Kirk, Paul F. Cannon, David W. Minter and J. A. Stalpers; CABI, 2008

Taxonomic history and synonym information on these pages is drawn from many sources but in particular from the British Mycological Society's GB Checklist of Fungi and (for basidiomycetes) on Kew's Checklist of the British & Irish Basidiomycota.

Acknowledgements

This page includes pictures kindly contributed by David Kelly.

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