Slippery Jacks Suillus — the slimy boletes of PNW conifer forests
Suillus are the slimy-capped boletes of conifer forests. Pick one up and you’ll know immediately — the cap is coated in a thick, slippery gluten that sticks to everything. Each species partners with a particular group of conifers: two- and three-needle pines, five-needle pines, Douglas-fir, or larch. If you know the trees, you can narrow down which Suillus you’ve found.
Dozens of species occur in the Pacific Northwest. Some are genuinely slimy, others dry and scaly. None of the PNW species is known to be toxic, though several are sour or slimy and a few people react to them (see Edibility). They are among the most common boletes in the region, and in fall the fat jack is among the mushrooms you’ll see most often under Douglas-fir.
Find Pine & Fir Forests on Forayz
Suillus species are linked to specific conifers. Use Forayz to scout ponderosa pine, shore pine, and Douglas-fir stands across the PNW.
Identification
| Feature | Description |
|---|---|
| Cap | 4–15 cm across, convex becoming flat. Surface ranges from extremely slimy and glutinous (most species) to dry and hairy/fibrillose (S. lakei). Colors span yellow-brown, chestnut, olive-brown, and orange-brown depending on species. |
| Pores | Small, round to angular. Yellow to olive-yellow, sometimes bruising brown or blue. No gills — this is a bolete with a spongy pore surface underneath. |
| Stipe | Often short and stocky. Many species have glandular dots (tiny raised specks that darken with age); others, such as S. brevipes and S. lakei, lack them. Some have a ring or veil remnants; others have no veil. |
| Veil | Present in some species as a partial veil leaving a ring on the stipe (S. luteus, S. lakei, S. caerulescens), sometimes thin and soon gone (S. pseudobrevipes). Others have no veil (S. brevipes, S. tomentosus). Veil color varies — white, purplish, or yellow. |
| Flesh | Pale yellow to whitish. A few stain blue, slowly: S. tomentosus mainly in the cap, S. caerulescens in the stem base. S. lakei slowly stains pinkish red. Many do not change color. |
| Spores | Olive-brown to cinnamon-brown in deposit. |
| Habitat | Always under conifers. Each species is mycorrhizal with a particular group: two- and three-needle pines, five-needle pines, Douglas-fir, or larch. |
Slimy cap + conifer partner = Suillus
A bolete with a sticky or slimy cap under pines or Douglas-fir is most likely a Suillus, especially with glandular dots on the stem. But not every Suillus is slimy or dotted, and other boletes can be tacky when wet (the king bolete’s cap is thinly viscid in rain). S. lakei is the common dry one: a scaly reddish cap, no glandular dots, and growth with Douglas-fir.
Key PNW Species
These six are among the Suillus most often recorded in Oregon and Washington. Learning their tree associations is the fastest path to identification.
Western Painted Suillus
Suillus lakei
The oddball — dry to barely tacky instead of slimy. Young caps are covered in fibrous reddish to orange-brown scales over a yellowish base, though the scales can wear off with age. A white veil leaves a band-like ring that may disappear. Usually under Douglas-fir, also in high-elevation hemlock forest. The second most recorded Suillus in Oregon and Washington.
Purple-veiled Slippery Jack
Suillus luteus
The classic slippery jack. Cap smooth and very slimy, dark brown to reddish brown. A thick white veil with a purplish, jelly-like underside forms a flaring skirt on the stem. Introduced from Europe: mostly in towns with planted Scots pine, but spreading into native pine forest.
Short-stalked Suillus
Suillus brevipes
Slimy, brown cap that fades with age, and no veil or ring at all. The stem is short, white, and usually without glandular dots. Common under two- and three-needle pines across Cascadia, especially in coastal dune forest and on the east side of the Cascades. One of the better-tasting slippery jacks.
Blue-Staining Slippery Jack
Suillus tomentosus
Yellow to golden cap covered with small fibers or scales, grayish at first and reddish brown later; sticky but not thickly slimy. The stem is covered in glandular dots. The flesh slowly turns bluish, best seen by pinching flesh from the middle of the cap. Under two- and three-needle pines, especially shore pine on the coast and lodgepole in the mountains. Edible but very soft and sometimes sour.
Suillus pseudobrevipes
Like S. brevipes, but usually sturdier, with a paler yellowish to honey-brown cap and a thin whitish veil that leaves remnants on the cap edge and a slight ring that may disappear. Common under shore pine in coastal dune forest and under ponderosa pine; fruits in fall, and on the east slope of the Cascades fairly often in spring too. Edible, but soft, slimy, and sour.
Fat Jack
Suillus caerulescens
Medium to large, with a buff to yellowish-brown cap that is dry to slightly sticky, and a white veil leaving a band on the stem. The stem base slowly stains bluish when scraped — the species name means “becoming blue.” Under Douglas-fir, not pine. Few mushrooms in Cascadia are more plentiful: it comes up in huge numbers once the fall rains begin (Siegel & Schwarz, Mushrooms of Cascadia). S. ponderosus, also with Douglas-fir, is very hard to tell apart, especially in age.
Habitat & Where to Look
Every Suillus species is mycorrhizal with conifers. Know the tree and you have a head start. Here’s the breakdown for the PNW:
- Two-needle pines (lodgepole, shore pine, planted Scots pine): S. brevipes, S. tomentosus, S. pseudobrevipes; S. luteus mainly with planted Scots pine
- Three-needle pines (ponderosa): S. brevipes, S. pseudobrevipes, occasionally S. tomentosus
- Five-needle pines (western white pine and others): S. americanus, S. subalpinus, S. acidus
- Douglas-fir: S. lakei, S. caerulescens, S. ponderosus
- Larch: S. ampliporus, S. ochraceoroseus
Coastal dune forests with shore pine are a reliable habitat for S. brevipes, S. pseudobrevipes, and S. tomentosus.
Where you find Suillus, look for spike-caps (Gomphidius) too. These slimy, gilled mushrooms are thought to parasitize Suillus and often fruit right beside them.
East of the Cascades, look under ponderosa pine at lower elevations and lodgepole at higher elevations. West of the Cascades, Douglas-fir forests reliably produce S. lakei and S. caerulescens.
Season & Timing
Suillus is overwhelmingly a fall genus in the PNW. The first fall rains start the flush, with October the peak by a wide margin. They taper through November and are mostly done by December. A few species also fruit in spring on the east side of the Cascades (S. lakei, S. pseudobrevipes), but spring and summer are a small share of observations.
Based on 12,031 iNaturalist observations from Oregon and Washington
The October spike is dramatic — more observations than all other months combined. Aim for October and early November. Several species appear in quantity once the fall rains arrive, so check pine and Douglas-fir forests once the rain returns.
Scout Conifer Forests with Forest Types
Forayz Pro includes forest type overlays showing ponderosa pine, lodgepole pine, and Douglas-fir distribution across the PNW. Match Suillus species to their tree partners before you head out.
Edibility & Cooking
No PNW Suillus is known to be toxic, and the common ones are edible. They are not everyone’s favorite: several are soft, slimy, or sour, and the fat jack and short-stalked Suillus are among the better-tasting ones. Here’s how to get the best results:
- Peel the cap. On the slimy species the cap skin peels off easily; grab an edge and pull.
- Pick young. Older specimens get waterlogged and buggy fast. Firm buttons with pores still pressed tight are ideal.
- Remove the pore layer on larger specimens if it’s gotten soft and spongy. Just scrape it off with a knife.
- Dry them. Soft, older specimens can be dried and powdered to use as a seasoning.
- Cook thoroughly. Like all wild mushrooms, eat them well cooked. Saute, stew, or add to soups.
A note on sensitivity: Some people react to S. luteus (Arora), and it can cause short-lived diarrhea if the slime isn’t removed (Lincoff). Handling S. americanus has caused an allergic skin reaction (A.H. Smith, via Arora). If you’re trying Suillus for the first time, peel the cap and eat a small amount.
Try the Bolete Finder
Identify PNW boletes step by step — including Suillus, Leccinum, and Boletus species. Answer questions about cap texture, pore color, and staining to narrow down your find.
Sources: Mushrooms of Cascadia (Siegel & Schwarz, 2024); MycoMatch (© Ian Gibson), a compilation of published descriptions through which most other field-guide authors named here are quoted; iNaturalist observations.