How to tell Birch knight from Tacked knight

The cap is 4–12 cm across, occasionally up to 15 cm. Young caps are convex, then flatten, often with a low umbo, and can be slightly sunken in the centre.

The colour is reddish brown to yellowish brown: darker in the centre, paler and yellowish at the margin. Fine brown fibres radiate from the centre. The skin is sticky, slimy and shiny in wet weather and matt when dry. The margin is often grooved, and old caps may crack into small scales.

The cap is 5–15 cm across. Young caps are hemispherical to convex with an inrolled margin, then flatten out, sometimes with a shallow dip in the centre when old, and the edge can be wavy. The surface is smooth, without obvious radial fibres, slimy and shiny when wet and tacky when dry.

The colour is reddish brown, chestnut or yellowish brown, paler and greyish pink towards the margin, which isn't grooved. The cap often has small dark yellowish brown spots that look like dried drops, but some caps have none.

The gills are crowded, fairly broad and notched where they meet the stem. Young gills are pale yellow or yellowish white, and with age they develop rusty brown spots, with brownish edges.

Yellowish gills are unusual in the genus: most knights, including the poisonous brown ones, have white or cream gills. The spore print is white.

The gills are white or cream, later pale brownish, crowded and notched or attached by a tooth at the stem. On old fruit bodies, and where they've been knocked, they develop rusty brown spots.

The spore print is white.

The stem is 4–13 cm tall and 0.7–2 cm thick, cylindrical, sometimes thickening towards the base. It's coloured like the cap but paler, yellowish brown, lighter at the top, and streaked with darker brown lengthways fibres.

Young stems are solid and slightly sticky; old ones become hollow. There is no ring and no volva.

The stem is 3–8 cm tall and 1–2.5 cm thick, cylindrical, sometimes slightly wider at the base, firm, and may become hollow with age. It's white, smooth or faintly fibrous, slowly browns with handling and age, and is rusty brown at the base.

There is no ring, no ring zone and no volva. Nor is there a sharply defined white band at the top of the stem; that's more typical of Tricholoma albobrunneum.

The flesh is firm. It's whitish to pale yellow in the cap and distinctly yellow in the stem, and that's the easiest way to tell the birch knight from other brown knights, whose flesh is white. It doesn't change colour when cut. The taste is mealy, sometimes slightly bitter.

The flesh is white and firm, sometimes brownish under the cap skin and at the stem base. It doesn't change colour noticeably when cut but slowly browns after long handling. The taste is mealy with a slight bitterness.

The smell is mealy, like raw dough, sometimes with a hint of cucumber. It's not much help for identification: some poisonous brown knights smell of flour too.

The smell is mealy, like fresh flour; some authors describe it as stale, sourish flour. It doesn't help with identification, because the edible poplar and matt knights smell of meal too.