How to tell Field mushroom from Garland roundhead

Cap 5–15 cm across, spherical when young, then flat or slightly umbonate. White or slightly creamy, cracking in dry weather; fibrous scales may appear as it matures. The margin is inrolled at first, then straight.

The cap is small, 2 to 5 cm across and only rarely up to 8 cm. It starts out hemispherical, becomes convex and finally almost flat, and in old specimens the margin may turn upwards.

The colour is lemon yellow, golden or ochre, a little darker in the centre, and it fades to pale yellow with age and sun. The surface is smooth and slightly sticky or greasy in wet weather, but it dries quickly, and old or dried-out caps can become finely scaly. Young caps often have white scraps of veil hanging from the margin.

Gills free (not reaching the stem) and crowded: soft pink at first, then bright pink, and chocolate-brown or blackish in mature mushrooms. Pink gills are a key safety feature that sets the field mushroom apart from poisonous species with white gills.

The gills are attached to the stem and crowded, with many shorter gills in between. They begin pale lilac-grey, turn purplish grey and end up dark purple-brown to almost black. The gill edges are paler and look slightly fluffy. The gills are the quickest way to rule out an Agaricus: field mushrooms have free gills that are pink when young.

The spore print is dark purple-brown to blackish. The spores are smooth and ellipsoid, roughly 7–10 × 4–5.5 µm.

Stem 4–8 cm tall, 1–2 cm thick, cylindrical, solid and straight. White. A firm membranous ring sits in the middle of the stem, a characteristic feature. No volva.

The stem is short and sturdy, 2 to 6 cm tall and 4 to 10 mm thick. It is white, sometimes yellowing with age, smooth or faintly fibrous, solid at first and later hollow. White strands of mycelium are often visible at the base.

The ring is the key feature. It is membranous, white and sits on the upper half of the stem, and it stays put as the mushroom ages. Its upper side is finely grooved, and as the cap matures the falling spores settle on it and darken it to purple-brown. There is no volva at the base.

Flesh firm and white; it turns slightly pink when cut or stays unchanged. It doesn’t turn yellow (yellowing is a sign of poisonous species). The taste is pleasant and richly mushroomy.

The flesh is white and firm, thick in the centre of the cap and thinner towards the edge. It doesn't change colour when cut or broken. The taste is mild, not bitter.

A pronounced smell of anise and almond with mushroomy notes, making it one of the most aromatic wild mushrooms. Cooking intensifies the aroma, and it can dominate the dish.

The smell is faint and slightly radishy, and sometimes barely there at all. Field guides don't describe a mealy smell for this species: that belongs to its dung-loving relative, the dung roundhead. So smell won't identify it; check the gills and the ring instead.