The horse mushroom (Agaricus arvensis) and the field mushroom (Agaricus campestris) are two widely distributed wild mushroom species that look very similar. They both have white caps and stems and grow in grassy areas, which often leads to confusion between the two. However, there are some key differences to look for when identifying horse mushrooms versus field mushrooms.
Appearance
-
The horse mushroom has a cap ranging from 5 to 20 cm across that is initially convex before flattening out It is white to pale brownish in color, smooth, and sometimes finely scaly.
-
The field mushroom has a smaller cap from 2 to 8 cm across, that is hemispherical when young before flattening. It is pure white and smooth.
-
Horse mushrooms have crowded gills that are pinkish when young, then mature to dark brown. Field mushroom gills are not as crowded and pinkish at first, becoming chocolate brown.
-
The stem of the horse mushroom is thick and solid, from 5 to 15 cm tall and up to 2 cm thick. Field mushroom stems are more slender.
-
Horse mushrooms have a double membranous ring on the upper stem. Field mushrooms have a delicate skirt-like ring.
Habitat and Season
-
Horse mushrooms grow in grassland habitats like pastures and meadows. Field mushrooms prefer grassy fields, meadows, and lawns.
-
Horse mushrooms appear from midsummer through autumn. Field mushrooms emerge from late spring through fall.
-
Horse mushrooms often grow in fairy rings while field mushrooms grow singly or scattered.
Odor and Taste
-
Fresh horse mushrooms smell strongly of aniseed. Field mushrooms have a mild mushroomy odor.
-
Horse mushrooms taste mild with a slightly sweet flavor. Field mushrooms have a more pronounced mushroom taste.
Yellow Staining
-
The toxic yellow stainer mushroom looks similar but stains bright chrome yellow when the flesh is bruised or cut.
-
Field and horse mushrooms may show some faint yellowing but not intense yellow staining like the yellow stainer.
-
Cut the very base of the stem and look for bright yellowing to rule out the yellow stainer lookalike.
Spore Print
-
Take a spore print to verify identification. The horse mushroom will have a dark purplish-brown spore print.
-
Field mushroom spores are dark brown. Yellow stainer spores are pale.
Edibility
-
Both the horse mushroom and field mushroom are choice edible species, though some people find horse mushrooms to be superior.
-
Always thoroughly cook wild mushrooms and eat a small portion the first time trying a new species.
By checking the characteristics of the cap, gills, stem, habitat, and spore color, you can reliably tell horse mushrooms and field mushrooms apart. Pay extra attention to yellow staining at the stem base to avoid confusion with the toxic yellow stainer. With caution and experience, you can safely enjoy these delicious wild treats.
Help keep this website free…
Phylum: Basidiomycota – Class: Agaricomycetes – Order: Agaricales – Family: Agaricaceae
This big, tasty mushroom can be found on roadside verges and permanent pasture. But if you’re picking mushrooms to eat, it’s not a good idea to include roadside specimens. Also, watch out for the Yellow Stainer, which looks a lot like the poisonous one and likes to live in grassy areas next to roads. Eating it can really make your stomach hurt. The Horse Mushroom, Agaricus arvensis, first shows up in the summer and usually keeps fruiting until the end of fall.
The Horse Mushroom is pretty common in Britain and Ireland, as well as in most of mainland Europe, parts of Asia, and North America. It has also been seen in Australia (where it is sometimes called the Almond Mushroom) and New Zealand.
The Horse Mushroom was first described by Jacob Christian Schaeffer in Bavaria in 1762. He gave it the name Agaricus arvensis, but like many other mushrooms, it spent some time in the genus Psalliota before going back to its original home in Agaricus. The Horse Mushroom is a cosmopolitan mushroom.
Synonyns of Agaricus arvensis include Agaricus arvensis Schaeff. , Psalliota arvensis (Schaeff. ) Gillet, and Agaricus fissuratus F. H. Møller. (Some authorities consider this to be a separate species; its cap cracks when old, and its spores are usually a bit smaller than those of Agaricus arvensis.) ).
The scientific name arvensis means “of the field” or “of the meadows,” which is a reference to where the Horse Mushroom usually lives. Less obviously, the common name may not be related to horses and its apparent love of horse manure (which is why you can often find this mushroom near stables or fields where horses graze), but some people think it is a reference to how big these mushrooms can get.
In New Zealand this species is commonly known as the Snowball Mushroom.
There are reports that this tasty and highly valued mushroom tends to store heavy metals like copper and cadmium. If you do decide to eat it, it should be more of an occasional treat than a free food bonanza when grassland mushrooms are in season.
CapThe cap of Agaricus arvensis matures at 8 to 20cm (exceptionally to more than 30cm) diameter. White but yellowing gradually with age, smooth or finely scaly, the cap is initially spherical and expands until it is flat or nearly so. The thick flesh is white and firm. The cap turns yellowish where bruised, and old caps often take on a yellow-brown tinge. |
|
GillsAt first pale pink, darkening and then becoming brown, the gills of the Horse Mushroom are free and crowded. |
|
StemUp to 10cm tall, the parallel stem usually a small bulb at its base and a robust, double ring with a cog-wheel form on the underside. The solid stem is smooth above the ring but sometimes finely scaly below. Its diameter ranges from 2 to 3cm. When cut at the stem base, Agaricus arvensis does not rapidly turn bright yellow – a useful visual distinction between this edible mushroom and the poisonous Yellow Stainer, Agaricus xanthodermus, whose stem base turns chrome yellow as soon as its cut flesh is exposed to air. |
|
SporesEllipsoidal, smooth, 6-9 x 4-6µm. Show larger Spores of Agaricus arvensis Horse Mushroom Spore printDark purple-brown. |
|
Odour/taste |
Taste not distinctive. Strong odour of aniseed. (The rather similar Yellow Stainer has an unpleasant phenolic or inky odour – a useful way of distinguishing between the edible Horse Mushroom, which also bruises slightly yellow, and that toxic toadstool Agaricus xanthodermus.) |
Habitat & Ecological role |
Agaricus arvensis appears in manured meadows and beside bridle paths and other places where there is plenty of decaying organic matter, upon which it feeds saprophytically. The Horse Mushroom is one of the largest and most distinctive fungi in its genus, often forms fairy rings many metres in diameter in permanent pastures. |
Season |
August to November, typically a week or two later than the Field Mushroom, Agaricus campestris, with which the Horse Mushroom is sometimes confused. |
Similar species |
The poisonous Yellow Stainer, Agaricus xanthodermus, quickly turns bright chrome yellow when cut or bruised, and it smells of iodine or ink rather than of aniseed. Agaricus urinascens var. urinascens (syn. Agaricus macrosporus) is very similar in appearance but does not turn bright chrome yellow when cut or bruised.; it grows in open grassland and in woodland clearings. The specific epithet of its older synonym refers to the large (for an Agaricus species) size of the spores this mushroom – typically 11 x 6µm – which also distinguishes it from the Yellow Stainer. |
The Horse Mushroom is a good species to eat, and it can be used in any recipe that calls for large mushrooms like Portobello. It tastes great in omelettes and rissotto, and it has enough flavor to make soups or sauces that go well with meat.
Being sure that what you’ve found is a Horse Mushroom is the most important thing. If you think you might have found a Destroying Angel or a Yellow Stainer (Agaricus xanthodermus), you should not be so sure. The stem base color change fixes the first problem, and making sure the gills are pink or brown instead of white stops the second, which could be fatal. The cautious old mushroom gatherers maxim is so important: Never munch on a hunch. (There are not many incautious old mushroom gatherers!).
Two pictures of Horse Mushrooms—one at the closed-cup stage (above) and one at the top of this page—were taken by Dave Kelly. With his permission, these pictures are shown.
Fascinated by Fungi, 2nd Edition, Pat OReilly 2016, reprinted by Coch-y-bonddu Books in 2022.
BMS List of English Names for Fungi
The genus Agaricus in Britain, 3rd Edition, self-published, Geoffrey Kibby 2011
Funga Nordica: 2nd edition 2012. Edited by Knudsen, H. & Vesterholt, J. ISBN 9788798396130
Dictionary of the Fungi; Paul M. Kirk, Paul F. Cannon, David W. Minter and J. A. Stalpers; CABI, 2008.
Taxonomic history and synonym information on these pages is drawn from many sources but in particular from the British Mycological Societys GB Checklist of Fungi.
This page includes pictures kindly contributed by David Kelly.
Fascinated by Fungi. Back by popular demand, Pat OReillys best-selling 450-page hardback book is available now. The latest second edition was republished with a sparkling new cover design in September 2022 by Coch-y-Bonddu Books. Full details and copies are available from the publishers online bookshop…
What is the difference between horse mushroom, field mushroom and yellow strainer
FAQ
Is the horse mushroom edible?
What is another name for a field mushroom?
How to tell if a field mushroom is edible?