Scarlet Bonnet Identification Guide

The first impression

You find this species by kneeling. The setting is low, damp and mossy: a Sphagnum lawn at the edge of a bog, short moss on a heath among heather and crowberry, a needle-strewn bank under conifers, a damp dune slack, or the mossy shoulder of a woodland ride. What catches the eye is a spark of colour in the moss, a coral-scarlet to orange-red pinhead on a hair-thin pale stalk, no bigger than a match head. There may be one, or a loose scatter of a dozen over a square metre.

Set expectations for scale immediately. The cap is 5 to 15 mm across, the whole fruitbody rarely more than 5 cm tall, and the tissues are so thin that a rough grab crushes them. Take a small pot or a folded index card, cut the moss around a specimen, and lift it with a fragment of substrate intact so the base survives to be examined.

Reading the cap

The cap starts narrowly conical or egg-shaped, then expands to bell-shaped and finally broadly convex with a low central hump, with the margin remaining even or very slightly scalloped rather than inrolled.

Colour is the headline and it is also the trap. At its freshest the cap is a vivid coral-scarlet to orange-red, most intense at the centre. From the moment it opens, it fades, and it fades from the margin inward and from the outside toward the disc, so that a mature specimen is salmon-pink, apricot or nearly cream at the edge with only a warmer orange eye remaining at the centre. Old, sun-bleached or rain-washed material can be almost whitish-buff and easy to mistake for something else entirely. When judging colour, always base it on the freshest specimen present.

The surface is dry to slightly moist but never gelatinous or slimy, and there is no detachable elastic skin. Under a lens the cap is finely powdery when very young and translucently lined, so the gills show through as fine radial striations running perhaps halfway to the centre in damp conditions.

The gills

Gills are the spore-bearing surface, and the details here are worth reading with a hand lens. They are relatively distant rather than crowded, with typically somewhere in the range of a dozen to twenty reaching the stipe and shorter gills between them. Attachment is adnate to narrowly adnexed, sometimes with a very small decurrent tooth running a short way down the stipe, and never deeply decurrent.

Colour is whitish to pale cream, occasionally with a faint pinkish or peachy tinge, and the gill faces are noticeably paler than the cap, which gives a fresh specimen an attractive two-tone look when tipped over. The edges are even and concolorous or barely paler, without any dark edge line. Gills are thin and rather narrow, not thick and waxy.

The stipe and base

The stipe is 2 to 5 cm long and only 1 to 2 mm thick, cylindrical, equal, fragile and hollow, and it is translucent whitish to very pale yellowish or faintly flushed with the cap colour toward the apex. Under a lens the surface is smooth to very finely powdery at the top when young, becoming polished with age. It is dry, with no gelatinous or sticky coating, and there is no ring and no veil of any kind.

The base is the part most often lost in collecting. Done properly, you should see the stipe running down into moss or needle litter and ending in a small tuft of fine white hairs or strigose fibrils that anchor it and bind a few substrate fragments. There is no bulb, no disc and no rooting tail.

Flesh and colour change

There is scarcely any flesh to speak of: the cap is membranous and the stipe hollow. Nothing exudes when broken, there is no latex, no milk and no watery juice, and there is no bruising reaction; damaged tissue simply fades and dries. The odour is faint and unremarkable. Recording these negatives is genuinely useful because two of the groups that get confused with it do have distinctive textures or exudates.

Taking and reading a spore print

Getting a print from a cap this small takes patience but is worth it because it eliminates several look-alikes in one move. Cut the stipe off flush, place the cap gills-down on a microscope slide or a small piece of clean glass rather than on paper, and cover it with an upturned egg cup or a small jar to keep the humidity up and the draughts out. Leave it six hours or overnight.

The deposit is sparse and will appear as a faint ghostly ring on glass. Slide a piece of black card underneath to read it: the print is white to very pale cream. Under a microscope the spores are smooth and ellipsoid, and they stain blue-black in an iodine-based mounting fluid, which is a family character of the bonnets and a decisive laboratory confirmation.

Substrate and season

This is a small decomposer of moss, plant debris and litter in acid, damp habitats. Productive ground includes Sphagnum bogs and their margins, wet heath among heather, damp mossy conifer plantations with a needle carpet, dune slacks, and mossy grassy banks. It is not a wood-rotter and you will not normally find it fruiting from a log.

The main season is late summer through autumn, sometimes lingering into early winter in mild damp weather. Fruitbodies are short-lived, so the population you find on a wet weekend may be gone within days, and a site is best checked repeatedly rather than once.

Separating it from the look-alikes

Orange Bonnet, Mycena acicula. The most frequent confusion because both are tiny and orange-red. Look at the stipe: in Mycena acicula it is bright yellow to lemon-yellow, in clear contrast with the cap, and often minutely hairy under a lens, whereas here the stipe is whitish or only faintly tinted. The cap of Mycena acicula is even smaller, brighter orange with a yellow margin, its gills are yellowish rather than whitish, and it grows on small woody twigs and plant debris rather than in moss and needle litter.

Other pale bonnets such as Mycena flavoalba. Similar habitat in grassy and mossy places, but the cap is cream to pale yellow without any true scarlet or coral phase. Since the Scarlet Bonnet fades, judge only fresh specimens and check whether any young caps in the population show real red.

Waxcaps, Hygrocybe species. Several small red and orange waxcaps share the grassy and mossy setting. Their gills are the giveaway: thick, waxy in texture, often broadly attached or decurrent and far more widely spaced, and the fruitbodies are more substantial with a greasy or viscid cap in many species. Rubbing a gill between finger and thumb, a waxcap feels waxy and smears, a bonnet does not. Waxcaps also favour unimproved grassland while this species leans toward acid bog, heath and needle litter.

Orange Mosscap, Rickenella fibula. Grows in exactly the same moss lawns and is the same size and colour range, but its gills are strongly and obviously decurrent, running well down the stipe, its cap is centrally depressed rather than bell-shaped, and its stipe is finely pruinose all over.

Small orange Marasmius and Gymnopus species. Tougher, more pliant fruitbodies with wiry stipes that revive when wetted, typically on leaf litter and twigs, without the delicate translucent striate cap.

A quick field checklist

Acid mossy or peaty ground, a fresh coral-scarlet cap under 15 mm fading to salmon and cream from the margin, translucently striate when damp, distant whitish adnate gills, a thin dry translucent whitish stipe with a hairy base, no exudate, and a white spore print.