Alder boleteGyrodon lividus

The cap of the alder bolete reaches 4 to 10 centimeters across. When young it is convex with an inrolled margin; with age it flattens out, often with a wavy margin. The surface is smooth, sticky or slimy in wet weather and matte when dry. The color is clay-brown, yellowish ochre or light brown, darkening with age; when damaged, the surface may take on a darker tint. The flesh is thin, so the cap breaks easily.

The spore-bearing surface is made of tubes, but an unusual one: the tubes are very short, and the pores are small, angular and irregular, often elongated and interconnected, running noticeably down the stem. They are bright yellow or golden yellow, and when pressed or damaged the pores quickly turn blue, taking on a blue-green or blue-gray tint. This sudden bluing is one of the species' most distinctive features.

The stem is short and thin relative to the cap, 3 to 7 centimeters tall, often off-center or curved, and narrowing toward the base. At first it matches the cap — yellowish brown — and darkens to reddish brown with age. The surface is smooth. There is no ring and no volva. When cut, the stem flesh can also turn blue.

The flesh is soft, watery and pale yellow; when cut and exposed to air it turns blue, taking on a bluish-green tint. The taste is mild, bland and without bitterness. Because its watery texture quickly turns mushy, the mushroom has mediocre food value; only young, firm fruiting bodies are chosen for the table, and they must always be boiled.

The smell is faint, bland and typically mushroomy, with no sharp notes. Aroma is not a defining feature, so for identification rely on the small yellow pores that turn blue, the sticky clay-colored cap and the constant link with alder in damp places.