Amethyst Deceiver

Laccaria amethystina is one of a small genus of mycorrhizal mushrooms recognised by thick, waxy-looking, widely spaced gills, a fibrous stringy stem and a white spore print. The genus name refers to the lacquered look of the gill faces; the epithet amethystina to the extraordinary violet of a fresh, wet fruitbody.

"Deceiver" is a reference to how much this genus changes appearance with moisture. A cap that is saturated after rain is a rich amethyst purple; the same mushroom a day later on a drying bank may be pale lilac-buff or almost whitish on top, and only the gills retain a hint of violet. Beginners routinely record wet and dry specimens from the same troop as two different species.

The amethyst deceiver is a fixture of northern-temperate broadleaf woodland and can fruit in vast numbers along path edges. Because it partners readily with many trees and tolerates poor, acidic soils, it is one of the most reliably encountered mycorrhizal mushrooms of autumn.

Cap

1-6 cm across, convex then flattening and often becoming shallowly depressed or wavy-margined with age. Deep amethyst to lilac-purple when moist, drying to pale lilac, buff or greyish-white from the centre outwards. The surface is dry and finely scurfy or minutely scaly rather than smooth, and the margin is often faintly striate and irregularly lobed.

Gills

Thick, broad, distinctly widely spaced and adnate to slightly decurrent, coloured a strong violet that persists much longer than the cap colour. A white bloom of mature spores may dust the gill faces on older specimens, muting the purple.

Stipe

3-10 cm long and only 2-6 mm thick, equal or slightly swollen at the base, the same violet as the cap and covered in fine longitudinal fibrils that give it a twisted, wiry appearance. There is no ring and no volva; the base often carries lilac-tinted mycelium bound to leaf litter.

Flesh & spore print

Flesh is thin, pale violet and does not change colour when cut or bruised. The spore print is white, and the spores are globose with prominent spines - a microscopic feature that confirms Laccaria. Fruitbodies are tough and pliant, and the stem is stringy rather than brittle.

It grows on soil and in damp leaf litter and moss in broadleaf and mixed woodland, with a strong association with beech and oak; birch, hornbeam and conifers also serve as partners. It is most abundant on acidic, humus-rich, moisture-retentive soils, and often lines shaded path banks, ditches and hollows in dense troops.

The main fruiting period runs from late summer to late autumn, sometimes continuing into early winter in mild seasons. The species is widespread and common throughout Europe, and closely related purple Laccaria taxa occur in eastern North America and temperate Asia, where similar-looking populations may represent distinct species.

Laccaria amethystina is ectomycorrhizal, forming sheaths around the fine root tips of its host trees and exchanging soil-derived water, nitrogen and phosphorus for tree sugars. It is a broad generalist, partnering with a wide range of broadleaves and conifers, which is a large part of why it is so common and why it colonises disturbed ground and young plantations so quickly.

The genus is known for aggressive early colonisation of root systems, which makes it a pioneer partner for seedlings and saplings. Its dense troops recycle nutrients through the litter layer, and the small, soft fruitbodies are heavily used by fungus gnats, slugs and small mammals, making it an important seasonal link between tree roots and woodland fauna.

The Deceiver (Laccaria laccata) has the same thick, widely spaced gills, wiry fibrous stem and white spore print but is orange-brown to pinkish-tan throughout, with no violet in the gills at any stage. Laccaria proxima is larger and more russet, with a distinctly scaly cap and a coarsely fibrillose stem.

Mycena pura is also lilac but has crowded, thin gills, a smooth polished cap, a hollow, snapping stem and a strongly striate margin. Purple Cortinarius species such as C. purpurascens or the smaller lilac webcaps differ in having a cobwebby veil on young stems and, decisively, a rusty-brown spore print instead of white. Faded amethyst deceivers can also resemble small pale Clitocybe, but those have crowded, narrow, strongly decurrent gills and no lilac tone on the stem.