Horse mushroom/ field mushroom
Agaricus arvensis, Agaricus campestris
Found: throughout NZ
These delicious mushrooms have the classic mushroom shape – a thick, whitedomed cap, thick white stem, and whitish gills that turn chocolate brown at maturity. Around the stem is a white ring, and the flesh tends to bruise slightly yellow when handled.
It's difficult to tell the difference between the many species in this genus.
“Macro characteristics make it extremely difficult to tell which species is which in the Agaricus genus,” says Tyler. “Most need microscopy to look at the spores to identify which is which. For example, Agaricus crocodilinus and Agaricus bernardii can look extremely similar.”
Field mushrooms are the most common find for foragers, says Tyler, but there are toxic Agaricus too.
“Agaricus sect. xanthodermatei, known as yellow stainers, are toxic. They won't kill you but will make you ill. They're distinctively identified by yellow staining at their base when cut vertically. They also have a phenol smell (sickly sweet, tarry), which is highlighted if a small piece is placed in the microwave for a few seconds.”
Many Agaricus species, including horse mushrooms, smell like aniseed, another critical identification feature.
Look for these mushrooms in autumn in open fields and pastures. They're known to grow in 'fairy rings' and will reappear year after year in the same location.