Birch Milkcap Identification Guide

Where you meet it

Damp birch woodland in late summer and autumn, with moss underfoot and bilberry or purple moor-grass around the trunks. Scattered through the moss are small tawny mushrooms, thin-fleshed, foxy orange-brown, with a slender stem and a cap that carries a tiny sharp point at the very centre. There are usually many of them, sometimes dozens across a hundred metres of birch stand, because this is one of the most abundant milkcaps of northern birch woods.

The first impression is of something modest and easily walked past: small, dull-coloured, unremarkable at arm's length. The identification is made close up, and it hinges on a test with a piece of white paper.

Reading the cap

The cap is 2 to 5 cm across, occasionally a little more. It begins convex, flattens, and finally becomes shallowly depressed, but almost always retains a small pointed umbo or papilla at the exact centre, like a raised pinhead in a saucer. That papilla is the most useful shape character.

Colour is tawny to pale cinnamon or dull orange-brown, sometimes with a faint pinkish or greyish cast, and it is essentially uniform: there are no concentric zones or spots. In wet weather the surface is slightly greasy and the colour darkens; on drying it becomes matt and paler. The margin is thin and often finely wrinkled or crimped, and it can be markedly paler than the disc, which exaggerates the apparent bullseye effect around the papilla.

The gills

The gills are pale cream to pale ochre with a distinctly pinkish or salmon flush, moderately crowded, and narrowly adnate to slightly decurrent, running a short way down the stem. Some blades fork near the stem attachment.

With age, and where handled or damaged, they discolour to a dull brown. Note that the discoloration follows the latex reaction described below rather than being an independent bruising response, so old specimens can look dirty brown along the gill edges.

The latex, and the tissue test

This is the character that names the species in practice. Cut across several gills, or nick the cap flesh, with a clean blade. A white latex appears at the cut, thin and often scanty, especially in dry weather. In a drought you may get almost nothing, so choose the freshest, wettest specimen available.

Now smear the droplet onto a white tissue, a white handkerchief or a corner of white paper. Wait two to five minutes and watch. In this species the smear turns a clear yellow, from pale sulphur to chrome. The latex on the gills themselves may also yellow slowly, and dried latex on the gill edge often leaves a yellowish stain that later browns.

Do the test in good light on genuinely white material, and always run it alongside a known-unchanging species if you are learning, because a faintly cream tissue can fool the eye.

Stipe, base and flesh

The stem is slender: 2 to 6 cm long and only 3 to 8 mm thick, cylindrical or slightly tapering, smooth and dry, coloured like the cap or a shade paler, often with a whitish apex. It is stuffed when young and hollow when mature, and it collapses easily under pressure.

At the base there is white mycelial down knitting moss stems and leaf fragments together. There is no ring, no veil remnants and no volva.

The flesh is thin, pale buff, watery and slightly brownish in the stem, and it does not change colour dramatically when exposed beyond the latex reaction and the gradual browning of damaged tissue. The smell is faint and rather indefinite in fresh material.

Taking a spore print

Cut a mature cap free at the stem, lay it gill side down on white paper, cover it with a cup and leave it four to eight hours. Because the caps are small and thin they dry out quickly and stop dropping spores, so a fresh, moist specimen matters more here than with a big fleshy fungus.

The deposit is pale cream to pale ochre-buff with a faint pinkish note. Scrape it into a ridge to read it properly. Under the microscope the spores are broadly ellipsoid with an ornament of ridges and warts forming an incomplete network, the standard pattern for the genus.

Substrate, partners and season

The Birch Milkcap is an ectomycorrhizal partner of birch above all, and occasionally of alder in the same wet ground. It grows on the soil, generally through moss, in damp birch woodland, birch carr, boggy heath edges and along wet woodland rides on acid soil.

The season runs from July to November, peaking in the main autumn flush, and fruitbodies are typically scattered rather than clustered. Because the fungus is so common and so variable in cap tone, it is worth checking the latex reaction on every collection rather than trusting the general appearance.

Separating it from look-alikes

Lactarius subdulcis. The beech equivalent, and the closest confusion by shape. Its cap is a deeper brick or reddish brown, usually without the sharp central papilla, and, decisively, its white latex does not yellow on a tissue but stays white as it dries. Habitat is beech rather than birch.

Lactarius rufus. Larger and much firmer, with a deep brick-red to dark red-brown cap and a prominent pointed umbo, often with pine as well as birch. Its latex is white and unchanging on paper, and the whole fruitbody has a tougher, more substantial feel.

Lactarius quietus. An oak associate. The cap is dull brown with faint concentric zones or watery spots, the latex is creamy white and unchanging, and the fruitbody carries a strong, distinctive oily smell that the birch species lacks.

Lactarius hepaticus. Also yellows its latex on a tissue, so this one must be separated on other grounds. It grows with pine on acid sandy soil rather than with birch, its cap is a darker liver-brown or chestnut, and it lacks the pronounced central papilla and pale crimped margin.

Lactarius chrysorrheus. With oak. Its latex turns bright yellow within seconds in situ on the cut surface, not merely after transfer to paper, and the cap is a paler ochre-pink with clear concentric zoning and thicker flesh.

Lactarius serifluus and L. cimicarius. These weep a watery, serum-like latex rather than a milky one and carry a very strong smell often likened to bedbugs or chicory.

Brittlegills (Russula). Similar size and habitat, but they exude no latex at all, which resolves the question in one cut.

Field checklist

Small tawny to cinnamon cap with a small sharp central papilla; no zoning; pale crimped margin; pale ochre-pink slightly decurrent gills browning with age; slender hollow stem; white latex that yellows on a white tissue in a few minutes; pale cream to buff spore print; birch on damp acid ground, July to November.