#160: Suillus luteus, the Slippery Jack

Often called the “Slippery Jack,” Suillus luteus is a fall bolete notable for its extremely slimy cap. Although you might think this texture is unsuitable for the table, the Slippery Jack is actually eaten fairly regularly. People who do eat this mushroom must make sure to peel off the upper surface of the cap. This is done for two reasons: the slimy layer does not have a very good texture and contains toxins that may cause some gastrointestinal distress.ⁱ

Description

S. luteus is a pretty good example of the genus Suillus (phylum Basidiomycota, class Agaricomycetes, order Boletales, family Suillaceaeⁱⁱ). Theoretically, mushrooms in Suillus can be differentiated from the rest of the boletes by their slimy caps, radially-arranged pores, the presence of a partial veil, glandular dots, and their coniferous habitat. Unfortunately, many Suillus mushrooms only display a couple of these characteristics.ⁱⁱⁱ S. luteus has all of these characteristics, except it lacks radially arranged pores.^iv

As mentioned above, one of the Slippery Jack’s most obvious characteristics is its very slimy pileus. Of course, S. luteus may not be very slimy during dry weather. You can still see evidence of the slimy layer because the cap often has debris stuck to it. In dried out specimens, the pileus will also become rather shiny. Aside from the slimy texture, the pileus is not very distinctive. S. luteus is a medium-sized mushroom, so the pileus grows to about 5-12cm across. Like most other boletes, it is circular and convex but flattens out in age. It is primarily brown in color, though it can range from dark brown to reddish brown to yellowish brown.^v

The pore surface of the Slippery Jack is whitish to light yellow and features very small pores. Unlike most other Suillus species, the pores are arranged randomly rather than like spokes (radially). The pores darken with age and may become yellow to greenish yellow when the mushroom is mature. Spores produced in the pores are colored brown. In young mushrooms, the pore surface is covered by a partial veil. This veil is mostly white and breaks open to reveal the pore surface when the mushroom begins to produce spores. On mature mushrooms, remnants of the partial veil can be seen as a ring around the stipe and small pieces of tissue along the cap margin.^vi

The most prominent feature of the stipe is the fairly thick ring left by the partial veil. Initially, the ring is white. However, it slowly discolors purplish, especially on the lower surface. Above the ring, the stipe is whitish and fades into the color of the cap near the top. This part of the stipe is also decorated with numerous clumps of cells called glandular dots. These glandular dots darken with age and stand out from the rest of the stipe when mature.^vii Glandular dots result from swollen cells and resemble tiny bumps more than scales or hairs. This is a feature unique to the genus Suillus, so finding it helps shorten the identification process.^viii Below the ring, the stipe is whitish and undecorated but discolors brownish purple as the mushroom ages. S. luteus is a rather squat mushroom; the stipe grows only 3-8cm long. The stipe is proportionately thick, growing between 1 and 2.5cm in width.^ix

Ecology

S. luteus can be found in North America, Europe, and Asia^x growing under conifers, particularly Scots pine.^xi Like the rest of the boletes, S. luteus is mycorrhizal.^xii Suillus species are usually found under conifers,^xiii and S. luteus fits this pattern.^xiv In particular, it grows underneath pines like Scots pine^xv (a European species).^xvi This mushroom was apparently introduced to North America from Europe, so in North America it is most common in Scots pine plantations.^xvii Plantations of red pine and eastern white pine are also good places to look for the Slippery Jack.^xviii The mushrooms primarily fruit during the fall^xix but may also be found in late summer or over winter during warm weather.^xx When it does fruit, it is often quite plentiful.^xxi

Edibility

The Slippery Jack is considered an edible mushroom, although it is known to cause gastric upset on occasion. To reduce the likelihood of poisoning, the slimy upper surface of the cap should be removed along with any remnants of the partial veil on the stipe. This also ensures that any dirt, leaves, and other detritus that have gotten stuck to the slimy cap are removed.^xxii Additionally, some people have an allergic reaction upon touching S. luteus that is similar to poison ivy. Other Suillus species can also induce this reaction, though it is relatively rare and affects only sensitive people.^xxiii

Slippery Jack mushrooms are generally not eaten fresh. Instead, they are usually dried first and later reconstituted (by soaking the mushrooms in water). This enhances the flavor of the mushrooms and allows them to be easily preserved. Younger mushrooms tend to have a better flavor, so try and pick ones where the partial veil has not quite broken to reveal the pores.^xxiv