• Proposed
  • Under Assessment
  • Preliminary Assessed
  • Assessed
  • VUPublished

Agaricus pattersoniae Peck

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Scientific name
Agaricus pattersoniae
Common names
IUCN Specialist Group
Mushroom, Bracket and Puffball
Assessment status
IUCN Red List Category
VU C2a(i)
Proposed by
Else Vellinga
Else Vellinga
Christian Schwarz
Else Vellinga

Assessment Notes

Taxonomic notes

Originally described as Agaricus pattersonae.

Why suggested for a Global Red List Assessment?

Restricted to mature Cupressus macrocarpa stands with an undisturbed duff layer in central coastal California, threatened by developments, decline of Cupressus due to infection with Seiridium cardinale, and increasing drought.
Conservation of mature Cupressus macrocarpa stands and younger stands that will provide the habitat in the future will effect a number of species that is restricted to this habitat, such as Lepiota,  Leucoagaricus species, and other Agaricus taxa.
Vulnerable under criterion C1 (ai). The number of known localities is small (less than 50) and the number of mature individuals in each subpopulation is definitely smaller than 1000.
Near Threatened under criterion A3(c). A decline in the number of sites is projected due to decline of the trees and habitat loss due to development and disturbance.

Geographic range

Known from the central coastal region in California (USA): Sonoma County southwards into San Luis Obispo County.
A few reports are from the eastern part of the USA but these have to be confirmed.

Population and Trends

Known from less than 50 sites based on collections (Mycoportal.org) and recent observations (2009-2015; Mushroomobserver.org) in California (USA).
Not declined yet, but prone to future decline of cypress groves.
Occurring in the original Cupressus macrocarpa stands, and secondary occurrence in planted stands.
Cupressus macrocarpa is native to California where it occurs in only two small stands, but is widely planted as windbreakers in coastal areas around the world.

Population Trend: Stable

Habitat and Ecology

Saprotrophic in duff of mature (over 40 years old) Cupressus macrocarpa stands and groves with an undisturbed duff layer, fruiting from (November)December through March, after heavy winter storms. These stands are only found in coastal areas of Central to southern California. Not occurring under solitary trees or stands with a well-developed herb and grass layer.


Cupressus macrocarpa is endemic to California, and occurs in two natural populations; planted groves exist, but are considered non-native and are threatened with replacement by native tree species.
Cupressus macrocarpa is prone to infection by Seiridium cardinale which damages and kills older and more exposed trees.
Habitat destruction is the main threat; for instance the cypresses at the type locality have been removed.
And lastly, due to the absence of late winter rains in the winters of 2012-2015 the species has not been fruiting in its usual localities.

Conservation Actions

Protect old monterey cypress groves, and make sure the habitat will keep to exist.

Research needed

Use and Trade


Kerrigan RW. 1979. Studies in Agaricus 1. Agaricus pattersonae. Mycologia 71: 612-620.

Peck CH. 1907. New species of Fungi. Bulletin of the Torrey Botanical Club 34:. 345-349.

Known distribution - countries

Regional Population and Trends

Country Trend Redlisted