Royal fly agaric

Like all Amanita species, the bulk of the organism lies beneath the ground as a symbiotic partner to certain species of trees. The fruit body of the fungus is a reproductive structure that appears when appropriate environmental conditions of moisture, temperature, and nutrient availability are met. The cap of A. regalis is 10 to 25 centimetres (4 to 10 inches) broad, and, depending on the stage of its development, can range in shape from spherical to convex to somewhat flattened. The color is yellowish brown, and it is densely covered with yellowish to light ochraceous scabby warts, which are arranged in almost regular concentric rings. The rings are a remnant of the volva left behind during expansion of the young fruit body. The cap is fleshy and when mature has grooves on the margin, which can extend 1.5 to 2 cm (1⁄2 to 3⁄4 in). The cap cuticle may be separated from the cap by peeling, to almost the center. The gills are crowded close together, free from attachment to the stem, and white with a creamy yellow tinge. The edges of the gills are floccose, meaning they have tufts of soft wooly hairs—another volval remnant. The stem of a mature individual is typically between 10 and 20 cm (4 and 8 in) long and 1.5 to 2 cm (1⁄2 to 3⁄4 in) wide, and spreads at the base into a bulb ornamented with 2–4 rings of small squamulose, lemon or ochre-yellow warts. …

A. regalis is more common in northern than south Europe, and it has not been reported from south and west Europe. In addition to being common in Scandinavian countries, it has been collected in Germany, Hungary, Latvia, Russia, Slovakia, and Korea. In North America, its distribution is restricted to Alaska, where it is usually found above the tree line. It is a rare species typically found growing on the ground in mountainous forests, both deciduous and coniferous. It is a mycorrhizal fungus, and exists in a symbiotic relationship with certain tree species. The system of fine below-ground threads, the mycelium, envelopes the roots of the trees and supplies them with needed minerals, trace elements and water from the soil, while the tree, in turn, supplies the fungus with food from its own supply, which it produces through photosynthesis. A. regalis has been shown experimentally to form mycorrhiza with birch, Scots pine, Mountain pine, and Norway spruce. Fruit bodies have been reported to grow in fairy rings.