Amanita frostiana : Frost's Amanita

Technical description not yet available.


Amanita frostiana is a rather small species of the eastern U.S.A. and southeastern Canada — extending as far northAmanita frostiana as boreal forest on the Island of Newfoundland. With the exception of some localities, it is not commonly encountered; and the great majority of supposed collections of the present species are found to be wrongly determined material of Amanita flavoconia G. F. Atk. However, the latter species has ellipsoid, amyloid spores and no persistent collar of volval material at the top of the bulb.

The cap of A. frostiana is a yellow-orange or orange-yellow with the disc sometimes more red-orange than the rest and has a striate margin. The volva is distributed over the “20 – 80 mm” wide cap in yellow, friable warts.

The gills are free, close, and cream in mass. The short gills are truncate to excavated-truncate and plentiful.

The white stipe is “47- 62 x 4 – 11” mm (94 x 6 mm in my only annotated collection) and bears a persistent annulus. The distinct and starkly white bulb (e.g., 17 x 15 mm) bears a white or yellow-white collar that is somewhat similar to the collar seen in the exannulate Amanita albocreata Atk.

The spores measure “7.0 – 10.2” µm wide and are “globose to subglobose” and inamyloid. Clamps are present at bases of basidia supporting the presumed relationship to A. muscaria var. muscaria (L.:Fr.) Pers.

This species is found in mixed forests with oaks and conifers. — R. E. Tulloss

Note: Dimensions in quotation marks are from (Jenkins, 1986).

Photo: R. E. Tulloss (northeastern U.S.A.)