King Bolete

Description

King Bolete is a large, common, and widespread mushroom. It has a cosmopolitan distribution throughout the temperate zone of the Northern Hemisphere, where it is found in Europe, Asia, North America, and Mexico. In the Southern Hemisphere, it has been introduced unintentionally in southern Africa, Australia, and New Zealand when tree plantations were established. It occurs in most of the contiguous United States, but it is absent from the Great Plains and the Great Basin, and it is mostly absent from the deep south except in the Appalachian Mountains.

At least 55 subspecies, varieties, and forms of Boletus edulis have been described. All but a few of these occur only outside of North America. Many of these are now considered distinct species, and many are now treated as synonyms. Whether the King Bolete of North America is a different species than the Porcini of Europe is a matter of continuing debate. At least five groups of mycologists are researching North American collections of King Boletes. They have identified fourteen “edulis-like” species. Until further research is done, most sources in North America do not recognize taxa below the rank of species. One exception is California King Bolete (Boletus edulis var. grandedulis). As the common name suggests, it occurs only in the far west.

King Bolete is found in deciduous and coniferous forests and in tree plantations, alone, scattered, or in groups, sometimes close together but not clustered (in troops). It can appear any time from spring through fall, but it is especially abundant after heavy rains in the fall. It grows on the ground under conifers, including pine, spruce, hemlock, and fir, and under hardwoods, including oak and birch. It has a mutually beneficial relationship (mycorrhizal) with the tiny rootlets of trees, absorbing sugars and amino acids while helping the tree absorb water.

When it first appears, the cap is convex, hairless, greasy or sticky, and light to dark orangish brown with paler margins. As it ages, the cap spreads out, becoming broadly convex or bun shaped. The mature cap is usually 3″ to 4″ (8 to 10 cm) in diameter, but it is sometimes up to twice that size. It is nearly flat and orangish brown or cinnamon brown, and it becomes tacky when wet. The surface may be smooth or somewhat pitted or pockmarked.

The pore surface is white or whitish at first, and it appears stuffed with pith. As it ages it turns pale yellow. On mature caps, the pore surface is olive yellow. It does not turn blue when bruised. There are 2 or 3 round pores per 1⁄32″ (1 mm), and the pores are up to 1⁄16″ (2 mm) deep.

The stalk is usually enlarged near the base when young. The mature stalk is white with brownish areas. It is usually 2″ to 4″ (5 to 10 cm) long and ¾″ to 13⁄16″ (2 to 3 cm) thick, but it is sometimes much longer and thicker. It may be club shaped, but it is often more or less the same thickness from top to bottom. The surface has a network of fine ridges (reticulate), at least near the top, due to the pores being pulled down the stalk as the stalk lengthens.

The flesh is thick, white, and firm. Unlike other boletes, it does not turn blue or otherwise change color when cut or bruised. It is edible, and it is much sought after in Europe.

The spore print is olive brown.

Similar Species

Habitat and Hosts

Deciduous and coniferous forests and tree plantations

Ecology

Season

Any time, but especially in fall