Tricholoma terreum: The Ultimate Mushroom Guide

About The Tricholoma terreum Mushroom

Tricholoma terreum is an edible gray-capped mushroom of the large genus Tricholoma.

This mushroom is found in Europe, where fruiting bodies appear under conifers, particularly pine and spruce, from late summer to late autumn. They may also arise in parks near these trees, and grow in fairy rings. They are generally in quite densely populated groups though not bunched. It has been recorded growing under exotic Pinus radiata plantations in Australia.

With a mild taste, the species used to be regarded as a good edible. However, some authorities recommend that inexperienced pickers avoid all grey tricholomas. Recent chemical tests show that this species may contain toxins that can cause rhabdomyolysis. However, from more recent investigations it has emerged that only an abnormal quantity of Tricholoma mushrooms may trigger the rhabdomyolysis and normal consumption of about 200g of mushroom is safe unless there is an individual reaction.

Other names: Grey Knight, Dirty Tricholoma.

Tricholoma terreum Identification

1. Ecology

   Mycorrhizal with conifers—especially with pines, but also with spruce, fir, and Douglas-fir—and more rarely with hardwoods, at least in Europe; growing alone, scattered, or gregariously; spring through fall; Europe and North America.

2. Cap

   4–7.5 cm across; at first convex with a central bump, becoming broadly bell-shaped or broadly convex; dry; finely, radially appressed-fibrillose or, with age, finely scaly; the margin usually finely woolly, especially in young specimens; gray to brownish gray.

3. Gills

   Attached to the stem by a notch; close; short-gills frequent; grayish; sometimes protected by a cortina-like veil in very young specimens.

4. Stem

   3–5 cm long; 1–1.5 cm thick; equal; bald; dry; whitish.

5. Flesh

   White; unchanging when sliced.

6. Spore Print

   White.

7. Microscopic Features

   Spores 5–8 x 3.5–4.5 µm; ellipsoid, with a small apiculus; smooth; hyaline in KOH; inamyloid. Lamellar trama parallel. Basidia 4-sterigmate; 30–35 x 5–7 µm; clavate. Cystidia not found. Pileipellis a cutis; elements 6–15 µm wide, smooth, hyaline or brown-walled in KOH. Subpellis clearly differentiated as a layer of inflated cells 10–25 µm across. Clamp connections not found.

Tricholoma terreum Look-Alikes

1. Tricholoma scalpturatum

   It is recognized by a strong farinaceous odor, a character lacking in T. terreum var. cystidiotum and a paler fibrillose-squamulose cap.

2. Tricholoma cingulatum

   Associated species with a pale grey fibrillose cap, is distinguished by a cottony white ring.

3. Tricholoma pardinum (common synonym Tricholoma tigrinum)

   Larger mushroom with a mealy odor; it is known to be slightly poisonous.

Tricholoma terreum Taxonomy & Etymology

When in 1762 he described this species, Jacob Christian Schaeffer called it Agaricus terreus. It was the German mycologist Paul Kummer who transferred it to its present genus in 1871, renaming it Tricholoma terreum.

Synonyms of Tricholoma terreum include Agaricus terreus Schaeff., Agaricus myomyces Pers., Gymnopus myomyces (Pers.) Gray, Tricholoma myomyces (Pers.) J. E. Lange, and Tricholoma bisporigerum J. E. Lange.

Tricholoma was established as a genus by the great Swedish mycologist Elias Magnus Fries. The generic name comes from Greek words meaning 'hairy fringe', and it must be one of the least appropriate mycological genus names because very few species within this genus have hairy or even shaggily scaly cap margins that would justify the descriptive term.

The specific epithet terreum is Latin and means 'earth' - a reference to the cap color of this mushroom rather than its growing medium.