Salty mushroomAgaricus bernardii

The salty mushroom (Agaricus bernardii), also called the salt-loving mushroom, is edible, but it pays to be choosy. It tastes like an ordinary field mushroom, yet many people dislike the smell, which is briny, fishy or sharp. It also likes salty ground and often grows by roads, and mushrooms from verges are best left where they are.

Only several features together identify it. It's a squat, very fleshy white mushroom: the cap is 6–15 cm across, and the thick stem is usually shorter than the cap is wide. With age the cap cracks into coarse brownish scales, and the margin stays inrolled for a long time. The gills are free and crowded, pink in young mushrooms, then reddish brown and finally chocolate, and the spore print is chocolate brown. The stem carries a single narrow ring with an upturned edge. There is no sac at the base.

Why does it turn red when cut? It's a normal feature of this species: the white flesh turns orange-red or reddish brown when cut or pressed, sometimes within minutes, sometimes only faintly. If, on the other hand, the cut stem base quickly turns bright chrome yellow and smells of ink or a hospital, you're holding the poisonous yellow stainer, which brings on nausea, vomiting, stomach cramps and diarrhoea 1–6 hours after the meal.

Where does it grow? It's one of the few mushrooms that thrive on salt. In Western Europe and Britain it was originally a coastal species of salt marshes, dunes and sandy grassland right by the beach, and from there it has spread inland along roads that are gritted in winter. In Ukraine its records come from steppe and open meadows: the Striltsivskyi Steppe reserve, steppe slopes in Crimea, floodplain hay meadows and the Tarutyne steppe, and lately also city lawns and verges in Kharkiv and Poltava. It grows on the ground singly, scattered or in groups, sometimes in fairy rings, and the cap often pushes up through the soil already covered in sand. The season is long, from late spring to late autumn, with one flush in late spring and early summer and another in early to mid autumn. It's uncommon: in Ukraine only a few dozen finds have been recorded.

Is it good to eat? Sources disagree. Some American and British authors rate it a good edible, like the pavement mushroom but chewier. Others call it mediocre: it is often maggoty, and the smell doesn't go away. It's cooked like any cultivated mushroom and needs no parboiling. Where you pick it matters more than how you cook it. A Czech study found that this species strongly accumulates silver from contaminated soil, so mushrooms from beside main roads, salted verges and industrial land aren't fit to eat.

How do you tell it from a death cap? This is the key question for any white Agaricus. The white form of the death cap and the destroying angel are deadly, and their young, closed buttons look like white field mushrooms. Amanita gills stay white at every age, while Agaricus gills are pink or brown. An Amanita has a loose sac, the volva, at the stem base, and an Agaricus has none. Amanitas give a white spore print, Agaricus a chocolate one. And Amanitas grow near trees, in woods, parks and shelterbelts, while the salty mushroom grows on open ground. So dig every mushroom up whole, because the base can sit deep in the soil, and slice closed buttons lengthwise. If the gills are still white, leave it. The first signs of death cap poisoning appear only 6–24 hours later, so at the slightest doubt call 112 (999 in the UK) straight away, without waiting for symptoms, and say you ate wild mushrooms.

Other look-alikes. The pavement mushroom grows in the same trampled ground by roads and paths, but it has a double ring, hardly reddens and doesn't smell fishy. The field mushroom is smaller, with a slimmer stem and a thin ring, and grows in pasture. The white dapperling is also white, ringed and found on lawns, but its gills only turn faintly pinkish and its spore print is whitish, never chocolate.