American Matsutake Identification Guide

First Impression and Setting

You rarely see American Matsutake before you see the ground it is lifting. The fruitbodies are heavy and strong, and they push up through packed conifer duff, needle mats and sand, cracking the surface into a low dome. Experienced observers scan for these mounds — often called mushrumps — rather than for mushroom caps, then open them carefully to find a firm white button beneath.

The forest type is specific. In the Pacific Northwest look under lodgepole pine, western hemlock, Douglas-fir and shore pine, often on sandy or well-drained soils near the coast, on old dunes, and on ridges. In the Sierra Nevada it appears with true firs and tanoak, and in eastern North America the closely related material grows under jack pine and white pine on sandy barrens. Ground cover is usually sparse: salal, huckleberry, moss, and deep needle litter. Fruiting is autumnal, roughly September through November inland and continuing into December or January along mild coastlines.

A note on names: western North American populations are now widely treated as Tricholoma murrillianum, with Tricholoma magnivelare in the strict sense in the east and Tricholoma mesoamericanum to the south. Morphologically they are near-identical and the field procedure below applies to all of them.

Excavating the Fruitbody

Because so much of the identification lives on the lower stipe, extraction matters. Loosen the duff around the mound with a stick or fingers and lift the whole mushroom with its base intact. A specimen snapped off at ground level has lost the sheathing veil pattern that makes the identification straightforward.

Reading the Cap

The cap is 5 to 20 cm across, sometimes larger, thick and hard, convex or nearly spherical when young and flattening only at full maturity. Young caps are white and dry, with a surface of fine appressed fibrils.

As the cap expands and ages it acquires cinnamon, tawny or reddish-brown flattened fibrils and patches, usually beginning at the centre and spreading outward, so an old cap can be mostly brown over a white ground. Bruised or weathered areas discolour brownish. The margin stays inrolled for a long time and is cottony, often carrying shreds of the partial veil.

The Gills

The gills are white to cream, crowded, narrow to moderately broad, and — critically — attached to the stipe with a notch, sinuate or emarginate, rather than free from it. Look at the junction closely: the gill runs toward the stalk, dips upward in a shallow curve, and meets it. This is the Tricholoma attachment and it is the fastest way to reject Amanita relatives.

Handled gills, or old ones, stain rusty brown to pinkish-brown. Gill edges are even. There is no latex and no brittle, chalky snap.

Stipe, Veil and Base

The stipe is 5 to 15 cm long and 2 to 4 cm thick, solid, dense and firm, cylindrical or tapering to a somewhat pointed base. There is no bulb and no volva.

The veil is the centrepiece. A thick, cottony-membranous partial veil covers the young gills and, on expansion, leaves a large flaring ring high on the stalk. Above the ring the stipe is smooth, white and slightly powdery or silky. Below it the stipe is sheathed in a cottony, fibrillose covering that breaks up into brownish patches, bands and belts against a white background, in a pattern like a rolled-down stocking. Note the sharp boundary between the smooth white upper stipe and the patchy sheathed lower stipe.

Flesh, Colour Change and Odour

Split the fruitbody lengthwise. The flesh is thick, white and very firm, unusually solid for a gilled mushroom, and it does not change colour immediately on cutting; over hours it may discolour to pale brownish, particularly where insects have tunnelled.

Smell the cut surface. There is a strong, distinctive, spicy and resinous aroma, penetrating and unlike ordinary mushroom smells. Odour is a legitimate morphological character and here it is one of the most reliable, since even a fragment retains it.

Taking a Spore Print

Cut off the cap, set it gills-down on white paper with a dark strip beneath one edge for contrast, cover it, and leave it several hours. Mature caps deposit readily.

The print is white. Under a microscope the spores are broadly ellipsoid to nearly round, smooth, roughly 5 to 7 by 4.5 to 5.5 micrometres, and inamyloid in Melzer's reagent.

Separating It From Look-Alikes

Amanita smithiana is the species to work through carefully, because it is also white, ringed, and grows in the same Pacific Northwest conifer duff in autumn. Separate it on four points: its gills are free, not notched; its cap bears soft, white to buff, easily detached warts and patches rather than flattened brown fibrils; its stipe base is enlarged, sometimes rooting or club-shaped, with soft volval scales and crumbs, and it lacks the crisp boundary between smooth upper and sheathed lower stipe; and its partial veil is soft and friable, often collapsing rather than forming a persistent flaring ring. Its odour is faint and mealy, never strongly spicy.

Catathelasma species are also large, white and firm with a conifer habitat, but they carry a double ring, the gills are clearly decurrent down the stipe, and the base tapers into a deep-rooting point.

Tricholoma caligatum and T. focale share the sheathed stipe pattern but are smaller, with caps covered in coarse, dark brown to reddish-brown scales over a paler ground rather than fine appressed fibrils on white.

Russula brevipes is a stout white mushroom of similar habitats, but it has no veil and no ring, its gills are brittle and often decurrent, and the flesh snaps like chalk rather than tearing in fibres.

Agaricus species may look similar when young but have free gills that turn pink then chocolate brown, and a dark brown spore print.

Leucopaxillus and white Clitocybe species lack the sheathed stipe and the ring entirely.

Field Checklist

A hard white mushroom lifting the duff into a mound; cap white with appressed cinnamon-brown fibrils; crowded white notched gills staining rusty; thick solid stipe smooth above a large flaring ring and sheathed in brown-patched cotton below; base tapering with no bulb or cup; white spore print; strong spicy-resinous odour; autumn, conifer duff, sandy soils.