Stalked Scarlet Cup | Sarcoscypha occidentalis Identification Guide

First impression: red confetti on the litter

The setting is damp deciduous woodland in warm weather: a creek terrace, a bottomland flat under maple, elm, box elder or hickory, or the shaded margin of a ravine after several days of rain. What catches your eye is a scatter of small, intensely scarlet discs a centimetre or so across, held slightly clear of the leaf litter on pale stalks. They are almost always in groups, because a single buried stick will carry a dozen or more, and once you have found one cluster you usually find others within a few metres. The colour is startling against brown litter, but the size means most people walk past them.

Step 1: read the cup

Measure across the top. Cups are 0.5 to 2 cm wide, rarely a touch more. Young ones are shallowly bowl-shaped with an incurved margin; they open out to nearly flat saucers, and old ones may become slightly wavy, irregular or split at the edge. The inner surface, which is the fertile hymenium, is smooth and matt to slightly waxy, bright scarlet to orange-red, fading in exposed positions to salmon or pale orange. The outer surface is markedly paler: pinkish-white to almost white, and under a lens minutely downy or scurfy rather than shaggy. That strong two-tone contrast between vivid inner and pale outer surface is normal for the genus and worth registering as a genus check rather than a species check.

Step 2: the stalk, which decides the species

This is the character the common name advertises and the one that carries most of the weight. Sarcoscypha occidentalis has a genuine slender stalk, typically 1 to 3 cm long and only 1 to 2 mm thick, whitish to very pale pink, smooth or finely downy, often curved or leaning where it has grown out from the side of a stick. As a rule of thumb the stalk is longer than the cup is wide, which is never true of the spring scarlet cups. Do not judge this from a photograph taken from above; get down and look at the fruit body in profile, or lift it clear of the litter.

Step 3: flesh and colour change

Section a cup with a fine blade. The flesh is thin, whitish to faintly pink, and slightly rubbery or waxy rather than brittle. There is no milk or juice, no bruising reaction, no blackening. If a red cup fungus darkens strongly or exudes anything on cutting, you are not in this genus. The tissue stays flexible when fresh and becomes hard and brittle as it dries, often shrinking to an unrecognisable dark speck.

Step 4: follow the stalk to the substrate

Always trace the base. The stalk leads down to a small buried hardwood stick, a fragment of bark or a fallen branch, generally well decayed, soft and dark. It does not arise from bare soil, from dung or from conifer wood in any typical occurrence. Prise the stick out and you will often see a line of fruit bodies emerging along a crack. Confirming wood as the substrate rules out several unrelated red discs that grow on soil.

Step 5: spores, and why the print is unusual

This is a sac fungus, so spores are shot upward from the hymenium rather than dropped from gills. You can still take a deposit: rest a fresh cup, fertile face down, over a glass slide or dark card inside a covered container for a few hours. The deposit is white to very pale cream, and best seen against dark glass. A quicker field trick is to bring a cluster from cool damp air into a warm room, or breathe steadily on it; a visible puff of spores may be released in a single silent cloud.

Under the microscope the spores are ellipsoid, colourless, smooth and comparatively large, roughly 18 to 22 by 8 to 10 micrometres, eight to an ascus, frequently with small oil droplets at the ends. Also examine the hairs on the outer surface: in this species they are short and straight or only gently wavy, which contrasts with the tightly coiled, corkscrew-like hairs found in one of the spring species.

Step 6: season and range as evidence

Season is a genuine identification character here rather than background information. This is the summer member of its genus, fruiting from late spring through to early autumn, with peak numbers in the humid weeks of midsummer. Its close relatives fruit in late winter and early spring, sometimes at the edge of snowmelt, and are usually finished before this species starts. Its range is centred on eastern and central North America. A small stalked scarlet cup found in July in Missouri or Kentucky is on very firm ground; the same shape found in March deserves a second look.

Separating it from look-alikes on structure alone

Sarcoscypha coccinea, S. dudleyi and S. austriaca. All are considerably larger, with cups 2 to 6 cm across, thicker flesh, and either no stalk or a short stout one that is shorter than the cup width. They fruit in the cold half of the year. S. austriaca additionally has strongly coiled outer hairs.

Microstoma floccosum. Similar scarlet colour and a stalk, but the cup is deeper, more goblet or urn-shaped, and is conspicuously clothed in long white hairs that give it a frosted, shaggy look. The hairiness is obvious with a lens and settles the matter.

Scutellinia scutellata and relatives. Sit flat on wet wood or soil with no stalk at all, are more orange than scarlet, and carry a fringe of stiff dark brown eyelash hairs around the margin.

Aleuria aurantia. Much larger, bright orange rather than blood-scarlet, sessile, growing on bare disturbed soil and path edges, with very brittle flesh.

Immature stinkhorn eggs and red slime moulds. Occasionally confused at a glance by colour alone, but neither forms a thin disc with a distinct fertile upper face on a slender stalk.

Field checklist

1. Scarlet disc under 2 cm, in a group, in warm-season deciduous woodland.
2. Distinct slender pale stalk, longer than the cup is wide.
3. Outer surface pale and finely downy, inner surface uniformly scarlet.
4. Base attached to buried, well-rotted hardwood.
5. Flesh thin and rubbery, no colour change, no exudate.
6. Pale spore deposit; smooth ellipsoid spores; outer hairs straight, not coiled.