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WSU/Pend Oreille Extension introduced the Sense of Place series in 1999, with a focus on local landscape and natural history of Pend Oreille County, Washington. A partnership with the Kalispel Tribe of Indians Natural Resources Department has allowed us to expand this program through EPA funding to include more classes, a newsletter and this website.

Truffles - the Seldom Seen

by Drew Parker

One needs little more than a passing interest in mushrooms to notice some peculiar aspects of these ephemeral organisms. They appear seemingly out of nowhere in unpredictable fashion, assume a multitude of strange forms, and turn up in all sorts of habitats. Soon they are gone, not to return until once again the conditions are just exactly right, whenever that may be.

As puzzling as the habits of wild mushrooms are, there is a group of fungi that is far more elusive and mysterious than the ones we might see scattered under the trees on a damp autumn day. These fungi are almost never seen while walking in the woods because they develop and produce spores while hidden below the soil surface. As their spores ripen, they enlist a variety of four legged forest dwellers to complete their life cycle.

These subterranean (hypogeous) fungi, collectively known as “truffles”, are typically round to irregular, firm lumps somewhat like small potatoes. The most well-known members of the group are the highly prized and priced European truffles of the gourmet trade such as the French black truffle (Tuber melanosporum), and Italian white truffle (Tuber magnatum). Along the coast of the Pacific Northwest on the west side of the Cascades there are three species of truffles that rival the European delights. They are known as the Oregon White Truffle (Tuber oregonense and Tuber gibbosum), and the Oregon Black Truffle (Leucangium carthusianum). These three species are presumed to be host-specific to the coastal variety of Douglas fir (Pseudotsuga menziesii var. menziesii), and it is under those trees that they are always found. Unfortunately, none of the aforementioned species are known to grow in the soils of Pend Oreille County. However, our truffle populations have hardly been studied, and therefore we really can’t know what might turn up in our forest duff.

Human mycophagy (eating fungi) is not really the point here, at least not in regard to forest ecology. Just about everywhere trees grow in the Pacific Northwest truffles are there with them, and in considerable variety. All truffles are connected to trees through their roots in an ancient and beneficial relationship known as mycorrhiza in which the fungi supply the tree with water and nutrients in exchange for some of the carbohydrates the tree derives from photosynthesis. Many, but not all, above ground (epigeous) mushrooms also form mycorrhizal relationships with trees and other plants. Without the mycorrhizal connection with fungi, forests would be stunted and much less vigorous than they are, thus fungi become important to the forester. On the other hand, from a mycologist’s perspective, it has been said that trees are the photosynthetic appendages of fungi.

By fruiting below the soil surface hypogeous fungi are less vulnerable to dry periods and frosty temperatures than their epigeous relatives. Almost all known truffle genera have closely related counterparts in the above ground mushroom groups. In fact most truffles are thought to have evolved from these above ground forms, adapting themselves to fruiting within the soil. Indeed there are numerous transitional forms in which the spore bearing structures of mushrooms such as gills, tubes, etc. have become convoluted and closed off, preventing the spores from being discharged. To survive underground a new method of spore dispersal becomes necessary. Truffles accomplish this by producing, depending on the species, a palette of aromas as the spores ripen that entices a variety of animals to dig them up and eat them. Animals known to dine on these odorous lumps range from insects to small mammals such as squirrels and voles, to the larger foragers, deer, elk, and bear. The spores pass through the digestive tract unscathed and so are effectively distributed throughout the landscape. Some animals such as certain voles and flying squirrels eat truffles almost exclusively, at times perched on a high branch nibbling away the truffle’s exterior and releasing the spores to waft away on the air currents.

Collecting truffles for the table is probably not practical for the casual forager, or even most avid mushroomers due to the difficulty in finding them and the lack of guidance in the literature. However, should you wish to locate some truffles to satisfy your curiosity by seeing them first hand, there are strategies that are helpful besides using trained pigs or dogs. Most kinds of trees are potential hosts for truffles with some exceptions such as cedar, maple, and orchard trees. Look for disturbances in the litter layer near trees made by animals as they forage for these aromatic fungi. Truffles tend to form at the transition zone between the organic humus layer and the mineral soil beneath it. They may develop along roots and near animal burrows. The tool of choice for truffling is the four pronged garden rake or cultivator, but in a pinch even a stout stick will do as a grubbing tool. Carefully peel back the top layer of soil and work your way inch by inch to the mineral soil normally not more than six or eight inches deep. Keep your excavations small and dispersed, and always replace the litter you remove.

If you are successful, identifying what you find can be just as challenging. There are few field guides that include many truffles. The more comprehensive guides like Mushrooms Demystified by David Arora, or the Audubon Field Guide to North American Mushrooms by Gary Lincoff list only a few. The best source of information is from the North American Truffling Society (N.A.T.S.), an organization of amateur and professional mycologists based in Corvallis, Oregon. View their website at http://www.natruffling.org/. This group will even identify your collections if you fill out one of their field data cards and send them the specimen. Truffles are a seldom seen but vital link in our wild land ecology, and getting to know them will reward the curious with a glimpse into the hidden complexities of life that surround us.


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