Q. What do they look like?
A. The color of the ascocarps varies from light to dark brown, and they range in size from a buckshot up to the size of a golf ball (occassionally larger). Some will be round, but most will have lobes and irregularities. They will be relatively dense, and the interior will be very firm, lighter in color, and have a conspicuously “marbled” appearance with alternating streaks of brown and white. They will also have a very strong earthy aroma.
Q. Where are they found?
A. In south Georgia, we find them in association with pecan trees, although apparently they can be found in association with other species of trees. They can be anywhere around the tree, although most abundant between the drip line and the trunk of the tree. Some specimens can be found protruding from the soil, but most are subterranean in the upper inch or two of soil.
Q. Do you find them in all pecan orchards?
A. No. They are usually found in well-irrigated orchards, particularly those with sprinkler irrigation. They tend to be in more crowded, shaded sections of the orchard, often in heavier clay soils, and on the shaded east and north exposures. We have found them on numerous varieties of pecans, but their distribution within an orchard is definitely not uniform. There may be numerous truffles under some trees, and very few or none under adjacent trees.
Q. Where did they come from and how do they spread?
A. Presumably the inoculum could have been introduced on the roots of pecan trees planted in the orchards. Alternatively, the fungus may have been present in these locations on native plants and simply found a compatible symbiont when the pecans were planted. The truffles themselves are the fruiting bodies of the fungus and contain thousands of spores. These spores are spread by wind and water, or often in the droppings of animals that consume them. They then germinate and grow in association with the roots of a new host plant.
Q. Why do they grow around trees?
A. The hyphae of T. lyonii and other truffles form mycorrhizae in association with the roots of certain plants. These relationships are mutually beneficial, with the fungus obtaining some nutrients from the plant. In return, it provides protection for the plant roots from pathogens and also enhances the availability of nutrients to the plant.
Q. When do you find them?
A. In south Georgia truffles usually appear in mid summer and last on into the fall, generally November. Late season specimens often start to degrade and get soft, and they do not weather a frost very well.
Q. How do you find them?
A. Although they may occur in other settings, they are most easily found in commercial pecan orchards. Growers often maintain weed-free strips around the trees, and these are prime locations for truffles. We have found them by simply raking the surface of the soil with a stiff-tined garden rake. Of course, a trained dog or pig would help since they are not usually visible above ground! They can be seen sometimes following pecan harvest where the soil surface has been swept clean by the harvest equipment. Truffles often reoccur in the same areas year after year, and harvest does not appear to be detrimental to future production.
Q. Is it safe to eat them?
A. The pecan truffle, as with other members of the Tuber genus, is considered nonpoisonous. As with any wild mushroom, however, it is an “eat at your own risk” situation. Specimens should be fresh and have a firm texture. Avoid older, darkened specimens, especially if they are noticeably softer than usual. Many cases of “mushroom poisoning” are simply cases of food poisoning. Truffles from commercial pecan orchards could also have low levels of pesticide residue, although the small quantities consumed would reduce the potential risk. One pesticide that should be avoided is aldicarb (Temik). This insecticide is highly toxic and is applied directly to the soil in some orchards. Although it is not known if aldicarb is found in truffles, DO NOT CONSUME TRUFFLES FROM ORCHARDS TREATED WITH TEMIK.
There are other fungi that can be mistaken for truffles. Puffballs are the most common. Several features distinguish puffballs from truffles. Puffballs usually are uniformly round or pear-shaped and grow above ground. They are often white and will have a sterile base or stalk. Fortunately puffballs are generally edible, except for the genus Scleroderma which will be purple when cut open. Potentially the most serious case of mistaken identity would be to consume a mushroom “button” (ie. small, unexpanded mushroom) from a highly poisonous genus such as Amanita. Slicing a mushroom button in half will reveal the stalk and cap instead of the uniformly marbled interior of a truffle. AS WITH ANY FUNGUS, IT IS IMPORTANT TO PROPERLY IDENTIFY IT BEFORE EATING.