Smith’s Earthstar

not listed

not listed

not listed

Until recently, this species was known as Hygroscopic Earthstar (Astraeus hygrometricus). Almost every North American field guide includes this mushroom under that name. Studies since 2003 found several new species that were previously included in A. hygrometricus. The type species A. hygrometricus occurs only in southern France and Turkey. Three species occur in North America. Only one, A. smithii, occurs in Minnesota.

Smith’s Earthstar is a late season, small or medium-sized mushroom—small when closed, medium-sized when open. It is similar in appearance to true earthstars in the genus Geastrum, but it is not even closely related. It is an example of convergent evolution, where species of different lineages evolve similar features. It appears on the ground in late summer and fall, singly, scattered, or in groups. It is found in sandy soil in forest edges, old fields, pastures, roadsides, and other disturbed sites. It has a mutually beneficial relationship (mycorrhizal) with the tiny rootlets of trees and shrubs, absorbing sugars and amino acids while helping the tree absorb water.

The fruiting body begins as a round to flattened case below the soil surface. It emerges as it expands and looks like a puffball. As it matures the outer layer of the case splits into 6 to 15 pointed rays, exposing a nearly spherical spore sac. When fully expanded, the fruiting body is ⅜″ to 3″ or more in diameter.

The rays are tough and leathery when moist, about 1 ⁄32″ (1 mm) thick, and more or less triangular. The upper (inner) surface is dark brown to black and is broken up into somewhat polygonal pieces. When fresh, it sometimes has a pale tan foreground with dark cracks and crevices, appearing like dried, cracked mud in a dry lake bed. The lower (outer) surface is covered with matted, blackish, hair-like fibers. When moist, the rays arch backward to the ground, raising the spore sac, and facilitating distribution of the dust-like spores. In dry conditions the rays fold back over the spore sac and become hard. Old specimens have blackish-brown rays.

The spore sac is stalkless, grayish or brownish, thin, papery, ⅜″ to 1¼″ in diameter, and more of less spherical or somewhat flattened. The outer surface is roughened by numerous particles. There is a poorly-defined opening (pore) at the top. The interior (spore mass) when young is white, solid, and divided into oval-shaped compartments. As it matures it becomes brown to cocoa-brown, and powdery. At maturity, the spore case ruptures through the pore at the top, and the spores are disbursed by the wind.

It is not edible due to the toughness of the rays. Similar mushrooms collected and eaten in Asia, once thought the same, have subsequently been identified as new species.

Disturbed sites; old fields, pastures, roadsides

Late summer and fall

Sources

4, 24, 26, 29, 30, 77.

Widespread in North and Central America. Common in the Great Lakes and coastal states. Less common in Minnesota.

Family
An analysis of the genus Astraeus (Ervin, Marion D. (1951) "Astraeus and Geastrum," Proceedings of the Iowa Academy of Science, 58(1), 97-99) concluded that the genus should be in its own family Astraeaceae. It was later moved to the family Diplocystidiaceae, but the move was not universally accepted. Some sources, including Index Fungorum, MycoBank, GBIF, and ITIS, place the genus in the family Diplocystidiaceae. Other sources, including NCBI, NatureServe, and iNaturalist, place it in the family Astraeaceae.

Species
The genus Astraeus was previously thought to contain a single highly variable species, Astraeus hygrometricus, with a worldwide distribution. In 1948 Scleroderma pteridis, found in North America, was transferred to the genus as Astraeus pteridis. Some authors treated it as a subspecies of Astraeus hygrometricus.

Molecular and phylogenetic studies since 2003 have identified several new species that were previously classified as A. hygrometricus. The most recent of these studies (Phosri et al., 2013) showed that the type species, A. hygrometricus, occurs only in southern France and Turkey. In the United States, western specimens were grouped under A. pteridis. Two new species were described, A. morganii in southern U.S. and Mexico, and A. smithii in central and northern U.S.

According to Michael Kuo (MushroomExpert.com), the 2013 paper “…is riddled with errors, inconsistent species descriptions, and poor documentation; I believe further research is required before accepting the paper's suggestions.”

… They were growing in very sandy soil. It is filling in with voluntary Jack Pines since the blowdown 2015.

Found several groups on the roots of uprooted trees.

Earthstar Mushroom

They don't last long. Happen to catch this one on the right day. Went back a few days later and it was shrinking.

Share your video of this mammal.

Location: Fairview Twp

… They were growing in very sandy soil. It is filling in with voluntary Jack Pines since the blowdown 2015.

Location: Fairview Twp, Cass County

Location: Carlton County, MN, near Nickerson

all over, around the cabin and driveway.

Location: Fairview Twp., Cass County

Found several groups on the roots of uprooted trees.

Location: Cass County

Location: Cass County

They don't last long. Happen to catch this one on the right day. Went back a few days later and it was shrinking.