Continuing our cool new monthly series, Mushroom of the Month, brought to you by Michael W. Hopping, co-author of A Field Guide to Mushrooms of the Carolinas:  A Southern Gateways Guide — this month it’s Painted Suillus, Suillus spraguei.

Mushrooms in the wild present an enticing challenge: some are delicious, others are deadly, and still others take on almost unbelievable forms. A Field Guide to Mushrooms of the Carolinas introduces 650 mushrooms found in the Carolinas–more than 50 of them appearing in a field guide for the first time–using clear language and color photographs to reveal their unique features.

A Field Guide to Mushrooms of the Carolinas is available now in both print and ebook editions.

Look for more Mushroom of the Month features on the UNC Press Blog in the months ahead.

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Painted Suillus, Suillus spraguei

Summer brings bolete season to the mushroom woods. More than a hundred kinds of these fleshy ground-dwellers are native to the Carolinas. Boletes resemble gilled mushrooms when seen from above, but pick one and turn it over. Where the gills ought to be you’ll find an undersurface like sponge rubber shot full of little holes or pores. Some species are erratic fruiters, perhaps appearing for a week or two every third year if and only if a Star Wars sequel rules the box office. Painted Suillus isn’t finicky in that way. Where there is Eastern White Pine, it pops up repeatedly from Memorial Day to Halloween.

Painted Suillus is an edible species with a cap diameter of 4-12 cm. The scruffy, burgundy red cap stands out well against a background of needle duff. Unlike most of its pine specialist cousins these mushrooms are dry, not sticky to the touch. Pores are fairly large, radially arranged, and yellow, bruising reddish brown. They are protected against premature exposure by a fibrous sheet of tissue called a partial veil. This tears away as the mushroom matures, leaving remnants on the cap margin and stalk. Stalks, like the caps, are clothed in red fibrils over a yellow background. The flesh inside both is yellow, often bruising like the pore surface. If Painted Suillus has a detectable smell, it is unpleasantly sharp, like an industrial chemical. That odor intensifies when the mushroom is cooked fresh, probably accounting for the mediocre edibility ratings it often receives. Dried and reconstituted prior to cooking, it does much better. Chopped fine, Painted Suillus imparts a grilled flavor to meats, soups, and sauces.

This species is limited to association with one type of pine. The story of what’s up with that offers a glimpse into the interconnectedness of plant life on land. From the fungal point of view it’s about sugar, the cellular equivalent of gasoline. Plants produce their own sugars via photosynthesis. Fungi, animals, and most microbes have to import their fuel supplies. The soil fungus that fruits as Painted Suillus accomplishes this by establishing mutually beneficial relations with a pine. In return for sugar, the tree receives water and minerals from its fungal partner. The trade occurs at nodules known as mycorrhizae, where feeder roots deactivate their interspecies rejection mechanisms and become encased with fungal threads.

Although Painted Suillus only pairs with Eastern White Pine, there’s no expectation of fidelity to a single partner. A fungal body or mycelium may be involved with multiple trees. The pines, and most other types of woody plant for that matter, connect to several mycelia, often belonging to various species of fungus. Considered at the level of forest, rather than individuals, the result is a community of networked trees. Studies of these linked systems have produced surprising results https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4497361/. Trees use mycorrhizal networks to share nutrients and chemical information with each other. Networked seedlings, for example, can survive longer under a dense canopy than would otherwise be the case. Incredibly, preliminary evidence suggests that mature “donor” trees might be able to selectively advantage their own kin, compared to unrelated seedlings of the same species.

Mycorrhizal relationships with woody plants are a common way of life for mushroom-producing fungi. Not to be outdone, the survival of a fungal group not known to make mushrooms depends on similar arrangements with grasses and herbaceous plants. Here, the trading happens at an even more intimate level. Mycelial threads are allowed to penetrate the plant roots, passing through microscopic gaps in cell walls, and then set up shop between one of them and an underlying cell membrane.

But I digress. Mushrooms are normally thought of as reproductive structures. And so they are. However, research into mycorrhizal networks shows us that mushrooms of Painted Suillus and other mycorrhizal species are also the natural equivalent of utility markers, signifying the underground presence of a living communications system with capabilities we’ve only begun to explore.

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Michael W. Hopping, a retired physician and author, is a principal mushroom identifier for the Asheville Mushroom Club. You can read his previous blog posts here.