Lake's Bolete Identification Guide

Standing Under Douglas Fir

This is one of the rare boletes where you can name the tree before you name the fungus and be most of the way there. Suillus lakei is bound to Douglas fir, Pseudotsuga menziesii, and to nothing else. In its native Pacific Northwest that means damp coastal and montane forest with a deep needle mat; in Europe, New Zealand and elsewhere it means planted Douglas fir stands, where it travelled with nursery stock and now fruits reliably in plantations and large gardens.

So the first move is to look up. Douglas fir has soft flat needles arranged all round the twig and distinctive cones with three-pointed bracts poking out between the scales; find those cones on the ground and the habitat half of the identification is done. Fruitbodies appear in the needle litter, on mossy banks and along trail edges, singly or in scattered groups, from late summer well into autumn and sometimes into early winter in mild coastal conditions.

First Impressions

What you notice is a medium-sized bolete with a dry, shaggy, brick to rusty-red cap, which is unusual for the genus. Most Suillus are slippery and smooth; this one is matted with fibrous scales. Caps run 5 to 15 cm, convex then flattening, with a margin that often carries hanging remnants of a whitish veil in young specimens.

Working Through the Cap

Look closely at the surface with a lens. The ground colour is a dull yellow or ochre, and over it lie appressed to slightly upturned fibrous scales in brick red, reddish brown or cinnamon. On young caps the scales are dense and the whole surface reads as red; as the cap expands they separate and the yellow ground shows through between them, so old caps look mottled or streaked rather than uniformly red.

The cap is dry to slightly tacky in wet weather but never carries the thick glutinous coat of the slippery Suillus species. The skin does not peel away in a clean sheet the way a glutinous pellicle does.

The Pore Surface

Turn it over and expect something coarser than the typical bolete underside. The pores are wide, angular and irregular, and they are arranged in radial rows running outwards from the stipe, sometimes almost forming shallow gill-like plates near the stipe apex. Colour is a dull to bright yellow, ageing dingy olive-yellow or brownish.

Press the surface with a thumb and watch. Most collections stain a slow dull brown or reddish brown where bruised; some show a faint blue-green tint, especially in wet material. The reaction is gradual, not the instant ink-blue of a blueing bolete.

The tubes are shallow, yellow, and run down the stipe slightly, and the whole layer is difficult to peel cleanly from the cap flesh.

Stipe, Veil and Base

The stipe is 4 to 10 cm long and 1 to 2.5 cm thick, more or less equal or slightly swollen, solid, and firm. Its upper part is yellow and finely dotted; below the veil zone it is streaked and smeared with reddish brown to brick fibrils that echo the cap.

The veil itself is the character to check next. Young fruitbodies have a cottony whitish partial veil stretching from cap margin to stipe. It tears as the cap expands, leaving either a soft, fibrous, collapsing ring or, more often, an untidy ring zone of cottony fibres with fragments still hanging from the cap edge. It is never a firm membranous collar.

Now the base. Slice the very bottom of the stipe across and look at the exposed flesh for a full minute. In most collections a distinct blue-green or greenish stain develops in the basal flesh, sometimes only as a narrow band. This is a well-known character of the species and it appears in the base far more reliably than higher up.

Flesh and Colour Change

Split the whole fruitbody vertically. The flesh is pale yellow throughout, deeper yellow near the tubes, sometimes with a reddish flush directly under the cap skin where the scales sit. On exposure it may stain pinkish, vinaceous or slowly brownish in the cap, while the stipe base does its blue-green trick. None of these changes is fast or dramatic, so give the cut face time before you decide it is unchanging.

Taking a Spore Print

Cut the stipe off flush with the tubes and set the cap pores-down on white paper under a bowl, in still air at room temperature, for six to twelve hours. Suillus caps are moist and the shallow tubes release spores steadily, so a good deposit usually forms overnight.

Expect a cinnamon-brown to olive-brown print, warmer and browner than the olive of the big Boletus species. Under the microscope the spores are smooth, elongate-ellipsoid and roughly 8 to 11 by 3 to 4 micrometres. A pale or pink deposit rules out Suillus entirely.

Substrate and Season

Ectomycorrhizal, obligately with Douglas fir. It grows from soil and needle litter, never on wood, and never with pine, spruce or larch, however similar the surrounding forest looks. Season is late summer to late autumn, extended in mild oceanic climates. Where Douglas fir has been planted outside its native range, this bolete is often the first Suillus to appear beneath it.

Separating It From Look-alikes on Morphology Alone

Suillus spraguei (also called S. pictus) is the closest visual match: a red, densely fibrillose-scaly cap over yellow ground with radial pores and a cottony veil. It is separated by its host, five-needle white pines, by a more strongly shaggy and often deeper crimson cap, and by flesh that stains pinkish rather than developing a green base.

Suillus ochraceoroseus is a larch associate with a pinkish to rose-ochre cap that is felty rather than sharply scaly, and yellow pores that are less strongly radial.

Suillus cavipes also grows with larch and has a dry, brown, hairy cap, but its stipe is distinctly hollow at maturity, which nothing in the lakei group is.

Suillus grevillei shares yellow pores and a ring, but its cap is smooth and thickly glutinous, golden to chestnut with no fibrous scales, and it grows only with larch.

Suillus luteus and Suillus granulatus are smooth, slimy, brown-capped pine associates with tiny round pores rather than wide radial ones.

Xerocomellus and Chalciporus species may have reddish scaly or cracked caps but lack any veil, lack the radial pore arrangement, and are not tied to Douglas fir.

Field Summary

Douglas fir overhead, dry brick-red fibrous scales over a yellow cap ground, wide angular radially arranged yellow pores, a cottony veil leaving a soft ring or ring zone, yellow flesh with a blue-green stain in the stipe base, and a cinnamon to olive-brown spore print.