Ruby Bolete Identification Guide

Where and How You Find It

Ruby Bolete is a small, slender bolete of open, grassy places rather than deep woodland. Look in mown park grass, churchyards, lawns with mature trees, woodland rides and clearings, hedge banks, and mossy grassy edges under oak, lime and beech. It is ectomycorrhizal, so it depends on those trees, but the fruit bodies frequently appear well out into the grass some distance from the trunk, following the spread of the root system.

It usually grows singly or in small scattered groups, and its modest size means it is easy to overlook in longer grass. The first impression is of a small mushroom with an intensely red cap, out of proportion to its slim stem, sitting low in turf.

The Cap

The cap is 3 to 6 cm across, occasionally reaching 8 cm, convex at first and then flattening. The surface is dry and matt, finely velvety when young and becoming smoother with age.

Colour is the headline: a strong blood-red, scarlet or crimson, sometimes with brick or purplish tones, fading to a duller brownish-red on old or sun-exposed fruit bodies. In dry weather the cuticle cracks into fine areolae, revealing pale yellowish to pinkish flesh in the network of cracks. The cracking is generally finer and shallower than in the classic coarsely cracked brown-capped species, but on a weathered specimen it can be pronounced.

The Pores

The pore surface is bright lemon-yellow when young, dulling through golden to olive-yellow as spores mature. The pores are relatively large and angular, and the tube layer is adnate to slightly decurrent, often running a short way down the stipe as a fine tooth.

Press the pore surface with a fingertip and watch. In Ruby Bolete the surface stains blue-green fairly promptly but not dramatically, and the stain later dulls to a brownish tone. The reaction is real but moderate, which is worth calibrating against the more explosive blueing of some relatives.

The Stipe

The stipe is 3 to 6 cm long and only 0.5 to 1.2 cm thick, cylindrical or slightly narrowed towards the base, and often curved where it grows out of turf. There is no reticulum.

The ground colour is yellow, clearest at the extreme apex and at the very base, but most of the stipe length is covered in dense fine crimson to carmine fibrils, dots and streaks, so at a glance the stem reads as red-striate. Handling produces a blue stain. Because the stipe is slender and the covering is fibrillose rather than netted, the texture is quite different from the raised mesh of a reticulate bolete, and running a fingertip up the stem tells you which you have.

The Base Check: the Genus Character

This is the observation that decides the identification, and it needs a knife.

Split the whole fruit body lengthwise from the cap right through to the extreme tip of the stipe base, then examine the basal flesh with a hand lens in good light. In Hortiboletus you will find scattered carrot-orange to coral-red punctate dots or granules embedded in the flesh of the stipe base. They can be few and easily missed, they show best in fresh, well-developed specimens, and they are strictly confined to the lowest part of the stipe.

Those orange dots separate Hortiboletus from the Xerocomellus species, which have no such granules. Make the split routine on every small red or brown bolete you examine and the group becomes far more tractable.

Flesh and Colour Change

The flesh is pale to lemon-yellow, with a reddish zone beneath the cap cuticle and a reddish tinge in the outer stipe cortex. On cutting it blues slowly and weakly, most noticeably in a band above the tubes and in the upper stipe, then fades. The odour is mild and unremarkable.

Record the strength and the location of the blueing, since in this group where the fungus blues matters as much as whether it blues at all.

Taking a Spore Print

Cut off the stipe, set the cap tube-side down on white paper, cover it and leave it for three to six hours. The deposit is olive-brown, the standard colour for the group and a useful check that you are dealing with a bolete relative rather than something else entirely.

Under a microscope the spores are smooth, spindle-shaped and around 11 to 15 by 4.5 to 6 micrometres, olive-brown in mass. Some close relatives show fine longitudinal striations on the spore wall, so a smooth spore surface here is a further point of separation.

Substrate, Season and Ecology

Ruby Bolete forms ectomycorrhizal associations, with oak and lime the most frequently cited partners, though beech and other broadleaves also serve. It tolerates disturbed and urban ground well, which is why parkland, verges, churchyards, playing-field edges and street plantings are such productive habitat. It appears on a range of soils and does not demand the lime-rich conditions some of its larger relatives prefer.

The season runs from early summer to late autumn. Fruit bodies are often colonised by the parasitic mould Hypomyces chrysospermus, which coats the fungus first in a white bloom and then in a powdery golden-yellow crust, deforming the pores and obliterating the cap colour. Finding a golden-furred lump next to a normal specimen is a common experience and a useful ecological observation in its own right.

Separating the Look-alikes

Hortiboletus engelii, also met under the name Hortiboletus bubalinus, shares the carrot-orange dots in the stipe base, so the genus character does not separate them. Use the cap: engelii is olive-buff, tan or dull pinkish-brown, never scarlet, and its stipe lacks the dense crimson fibrillose covering.

Xerocomellus chrysenteron is the classic confusion. Its cap is dull olive-brown to grey-brown and cracks coarsely, with pinkish-red showing in the fissures, which can suggest a red cap at a glance. Split the base: there are no orange granules. It also tends to blue more readily than Ruby Bolete.

Xerocomellus cisalpinus has a brown cap and blues strongly, particularly in the stipe base flesh, where the reaction is a clear blue rather than orange dots. Its spores are finely striate lengthwise.

The name Xerocomellus rubellus appears in older literature for this very species, so a specimen labelled that way is not a look-alike but a synonym, and it is worth knowing so the name does not confuse you.

Chalciporus piperatus is similarly small but has a cinnamon to tawny-buff cap, distinctly rusty to copper-red decurrent pores, and chrome-yellow flesh in the stipe base with no blueing.

Aureoboletus gentilis has a pinkish-red cap but a viscid, sticky surface in damp weather, bright golden pores, and no blueing.

Neoboletus luridiformis is far larger and heavier with a dark brown velvety cap, orange-red pores and instant, intense dark blueing throughout.

Suillellus queletii is also much bigger, with red pores and a distinctive deep beetroot-red flesh through the stipe base rather than scattered orange granules.

Field Checklist

1. Grassy parkland, lawn or woodland edge near oak or lime, growing from soil.
2. Cap 3 to 6 cm, scarlet to blood-red, dry, finely cracking when dry.
3. Pores lemon-yellow, angular, blueing moderately when pressed.
4. Slender stipe densely covered in crimson fibrils and dots, no network.
5. Flesh yellow, blueing slowly and weakly.
6. Split the base and find scattered carrot-orange dots in the basal flesh.
7. Spore print olive-brown; spores smooth and spindle-shaped.