Horse Mushroom
Agaricus arvensis · Family Agaricaceae · Updated October 2026
504US records
35states
Augbusiest month
504 US records since 1895 (94 in the last 10 years)
Last seen Sep 9, 2026 (about 7 weeks ago) near Virginia, St. Louis County, MN, photographed by an iNaturalist user, with the ID agreed on by other iNaturalist users (research grade). Most US records come from New Jersey, California and Pennsylvania, and the busiest months are Aug, Oct and Sep. (Data as of October 26, 2026; records can lag by weeks.)
⚠ Never eat a wild mushroom based on this site. We show where fungi have been recorded, nothing more. We never say any mushroom is edible or safe, and you shouldn't decide that from any website, app or photo. Many deadly mushrooms look like harmless ones. If someone may have eaten a wild mushroom, call Poison Control at 1-800-222-1222 right away.
Lookalike warning. Many mushrooms, including deadly ones, closely resemble each other, and the only reliable identification comes from an expert looking at the actual specimen (often with spore prints or microscopy). Never use a name, photo or record count on this page to decide what something is.
When it's recorded
Records by month, all years. Busiest: Aug, Oct, Sep.
Where it's recorded
Top counties
- Sussex County, NJ (36) · latest Sep 28, 2019
- Ocean County, NJ (29) · latest Oct 26, 2019
- Mercer County, NJ (24) · latest May 4, 2019
- Morris County, NJ (22) · latest Jul 20, 2019
- Burlington County, NJ (19) · latest Oct 6, 2018
- Hunterdon County, NJ (15) · latest Aug 25, 2019
- San Mateo County, CA (14) · latest Sep 13, 1978
- Rooks County, KS (13) · latest 1908-04
- San Francisco County, CA (13) · latest May 12, 1981
- Monmouth County, NJ (13) · latest Aug 22, 2015
More on this species from GBIF.
Bring along
🍄
Regional mushroom field guideSee on Amazon🍄
Folding mushroom knife with brushSee on Amazon🍄
Wicker foraging basketSee on Amazon🍄
10x hand lens / loupeSee on Amazon🍄
Spore print paperSee on AmazonAs an Amazon Associate we earn from qualifying purchases.