Amanita phalloides — Death cap
Left image: Death caps12 as they appear growing in grass. The distinctive cup (volva) is hidden below ground. The 'egg' stage of death caps look like puffballs (left image) but sliced in half (image to the right) the developing gills indicate the poisonous mushroom that is developing within. Photographs by Paul Kroeger.
Warning: Do not mistake the highly toxic death cap mushrooms for edible straw mushrooms (Volvariella volvacea). In BC and the Pacific northwest, a mushroom that looks like a straw mushroom is probably the far more common death cap. Other fatal mistakes are possible; see 'Cases of Poisoning' and 'Similar species'.
Odour: Mild initially, becoming pungent and unpleasant with age.
Taste: Do not taste this one. Although those who mistakenly ate death caps claimed the flavour was excellent, no one would want to repeat the resulting suffering.
Cap: 3–12 cm in diameter, at first rounded then opening to convex or flattening out to almost plane. Colour is variable but caps usually have a distinct greenish hue, olive yellowish to brownish to olive in the centre, often a bit streaked, becoming paler whitish to pale yellowish near the edge. Caps of old specimens are often brownish. The cap is usually bare, but its surface may have white, thin, flat patches of veil. When weather is wet, the cap is viscid or slippery. It develops a distinct satiny or metallic sheen when dry. Close examination of the surface of a young cap will not show the faint radial grooves that are present around the cap edge in many other amanitas. The flesh is white and does not discolour.
Gills: White, closely spaced and at first covered by a white veil; free from or narrowly attached to the stem.
Stems: 5–13 cm long and 1–2 cm wide, tapering slightly towards the top and expanding at the base to a soft bulb. The stem is whitish or shaded with cap colour below the ring and white above it.
Ring or veil: A membranous ring or veil initially covers the gills. Later, as the cap expands, the ring hangs like a skirt around the upper portion of the stem. The upper surface of the ring is white and slightly striate to smooth; the lower surface is shaded with the colour of the cap.
Cup or volva: A white, membranous, sac-like, loose to sheathing volva occasionally called the “death cup” surrounds the stem's expanded basal bulb. Unfortunately, the stem's base is often deep in the ground and if the base breaks off in the soil, its diagnostic cup can easily be missed.
Spores4: 7–12 x 6–9 µm, subglobose to ellipsoid, smooth, thin-walled and hyaline, amyloid (turning blue in Melzer's iodine reagent).
Habitat1: On the ground or in grass, especially in cities and suburbs. In mid-summer, death cap mushrooms may be found in irrigated lawns and grass strips. They are commonly associated with non-native, broadleaved trees in the birch family, especially with hornbeams (Carpinus sp.), and with non-native members of the oak family. In California, BC, and probably Oregon, death caps have been collected under native oaks as well. Ectomycorrhizal.
Geographical range1,6-8: Native to Europe, but introduced to North America and the Southern Hemisphere along with its host trees. In western North America, from southern California to BC. Commonly recorded from the urban and suburban areas of Vancouver, Victoria and Seattle and to be expected in other cities. Very common in western California in native and non-native habitats. In BC, the species has been spreading northwards and into native habitats.
Death cap mushrooms have been mistaken for straw mushrooms and eaten by accident but straw mushrooms are rare (occasionally found on compost heaps) or absent through BC and the Pacific northwest. Straw mushrooms have grey or brown caps and salmon-pink rather than white spores.
Death caps have been mistaken for puffballs. To distinguish between them, slice the ball-like structure in half from top to bottom. The entire inside of an edible puffball is uniform and white. The inside of an egg of a death cap is not uniform and within, a young mushroom with half-moon-shaped developing gills may be visible (see image above).
Older brownish death cap mushrooms can be mistaken for the Gypsy mushroom (Cortinarius caperatus) but the Gypsy differs in having brown spores and a wrinkled rather than smooth cap.
Death caps are similar to other species of Amanita from various parts of the world, some of which are edible. However, the consequences of a mistake are serious and eating any Amanita resembling a death cap could be a last meal.
When in doubt, throw it out.
Toxins9: Amatoxins, heat-stable cyclic peptides that are not destroyed by cooking. Amatoxins stop protein synthesis by inhibiting an essential enzyme, RNA polymerase II. Phallotoxins, cyclic peptides that bind F-actin are toxic but may play a limited role in poisonings as they are not readily absorbed through the gut.
Symptoms10: Time of onset 6-12 hours (up to 36 hours). Abdominal pain, vomiting, watery diarrhea: symptoms subside after about one day; then about 72 hours post ingestion, gastrointestinal symptoms recur along with signs of impending liver failure. In fatal cases death occurs 7-10 days after the first onset of symptoms.
Treatment: Contact your regional Poison Control Centre immediately if you realize you or someone you know has become ill after eating any amanita mushrooms. Poison centres provide free, expert medical advice 24 hours a day, seven days a week. If possible, save the mushrooms or some of the leftover food containing the mushrooms to help confirm identification.
British Columbia: 604-682-5050 or 1-800-567-8911.
United States (WA, OR, ID): 1-800-222-1222.
Cases of poisoning by death caps11: Death caps growing in British Columbia caused three serious poisonings including one fatality since they were first found here in 1997:
- In 2003 an adult man in Victoria ate what he thought were puffballs growing in his front yard. These turned out to have been undeveloped “buttons” of Amanita phalloides; a site visit later revealed several mature death cap mushrooms at this location under a mature English oak tree. The patient recovered after extended hospitalization.
- In 2008 an adult woman ate death caps that she had identified as the straw mushroom Volvariella volvacea growing on an agricultural property in Langley. After extended hospitalization she recovered.
- In 2016 a three-year-old child died more than a week after eating Amanita phalloides growing on a property in downtown Victoria.