Butyriboletus appendiculatus: The Ultimate Mushroom Guide
About The Butyriboletus appendiculatus Mushroom
Butyriboletus appendiculatus is an edible pored mushroom that grows under oaks and other broad-leaved trees such as beech. It often grows in large colonies beneath the oak trees and is frequently found cohabiting with old oaks in ancient woodland. Cap color varies from pale yellow to a more typical reddish-brown. Pale- to rich-yellow cap flesh may blue slowly & erratically. The common name refers to the butter-yellow stem, which may have subtle netting up high by the pores.
Like all Butter Boletes, this mushroom has a very firm and appealing texture. Likes oak.
DNA testing moved this mushroom from Boletus to a newly erected genus called “Butyriboletus” (“butyri” being latin for “butter” and this being one of the Butter Boletes). The species name “appendiculatus” is now reserved for a look-alike European species.
Other names: Butter Bolete.
Butyriboletus appendiculatus Identification
Convex to flattened, brown to yellowish-brown caps measuring 6–20 cm (2.4–7.9 in) in diameter. They have a dry to a slightly sticky surface texture that may develop cracks with age.
The mushroom has very firm yellowish flesh that may slowly change blue when cut or bruised. The pores on the cap undersurface are butter yellow, and may also bruise blue, although this is less likely in young specimens.
The stipe is 5–15 cm (2–6 in) long by 2–6 cm (0.8–2.4 in) thick at the top near the attachment to the cap and ranges from thicker at the base to equal throughout, to tapered at the bottom. It is also yellow, sometimes developing brownish to reddish stains, and may have fine reticulations near the top.
Individual spores are ellipsoidal to spindle-shaped, smooth, and measure 12–15 by 3.5–5 µm.
The Europe species Butyriboletus subappendiculatus is quite similar to B. appendiculatus in microscopic characters. It can be distinguished in the field by the lack of a bruising color reaction, more pallid cap colors, and growth under conifers. Also similar are Butyriboletus regius and Boletus edulis.
Butyriboletus appendiculatus Taxonomy & Etymology
The species was first described scientifically by German polymath Jacob Christian Schäffer in 1774 as Boletus appendiculatus. American Charles Horton Peck later used the name in 1896 for a species he found in Washington, but the name was illegitimate because Schäffer's earlier usage has priority. Until 2014, it was classified in the genus Boletus.
Molecular phylogenetic analysis demonstrated that it and other members of Boletus section Appendiculati were phylogenetically distinct from Boletus, and the genus Butyriboletus was created to contain them.
The specific epithet appendiculatus means "with a small appendage".
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