Poplar knight or Birch knight

The cap is 5-12 cm across, convex with an inrolled margin when young, later becoming flat and spread out with a slightly wavy margin. The skin is finely fibrous or smooth; slimy and sticky in wet weather, dry and matte when it's dry. The colour is reddish chestnut or reddish orange, richer at the centre and paler toward the margin. Old caps turn brownish chestnut with small cracks. The margin is even, with lengthwise grooves in damp conditions.

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 gills are notched (emarginate) where they meet the stem, moderately crowded and fleshy. They start out whitish and age to cream with rusty spots along the edges. Spore print white.

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 stem is 5-10 cm tall and 1-2.5 cm thick, firm and cylindrical, thickening toward the base when young. It's whitish at the top and brownish lower down, with ochre-chestnut spots, and smooth with lengthwise fibres. No ring.

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 flesh is firm and white, and where cut it slowly takes on a creamy brownish tint. The smell is faintly mealy; the taste is mild at first, then bitterish and mealy, with the typical Tricholoma aftertaste.

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.

Faintly mealy, with a hint of fresh cucumber — typical of many knights.

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.