This quick update will cover our recent project with Dr. Rytas Vilgalys, Professor of Biology at Duke University. Dr. Rytas was kind enough to do some PCR DNA and get an ITS sequence of some of our various collections of Pleurotus that were found growing on pine wood.

Over the past 2 years, James and I have been on the hunt for an oyster mushroom that grows on pine. To explain, I should first give a little background about these particular fungi. They tend to favor deciduous wood, especially poplar trees in Colorado. To most fungi, pine wood isn’t something easy to eat. Coniferous trees contain natural resins that tend to contain chemicals that are quite anti-fungal. This does not mean that fungi cannot eat coniferous wood, it is just quite difficult for them to do. However, Pleurotus are special fungi. They have discovered a quite efficient method of decomposing their substrate, excreting powerful digestive enzymes able to breakdown many different types of freshly cut wood. There is even a type of Pleurotus that can grow on cactus skeletons! The Pleurotus that James and I had found were growing from the cut stumps of pine trees and a spruce log growing at 10,000′ in elevation. These were cultured in our lab in Denver and were eventually sent to Dr. Rytas. He was interested in them because of their unique habitats they were found growing in and was wondering, as we were, if they were a possible new species of Pleurotus. He also received a few control collections of Pleurotus pulmonarius from various locations in the state, growing from cottonwood trees. These were tested against the mushrooms that were found growing on conifers. This testing is basically done by taking known sets of genes from a specific species of fungi and testing samples of DNA against those genes to see if they are similar enough to be the same genetic group (hopefully that wasn’t too over simplified?). Much to our surprise, every specimen came back as P. pulmonarius! It is well documented that P. pulmonarius grows occasionally from conifer, but these specimens also had unique morphological features that were distinctly different, even with indoor grown mushrooms in a controlled environment! Just goes to show that morphology sometimes can tell you very little about what type of fungi you have. We now know that our cultures of oysters collected from these conifer habitats are P. pulmonarius, but have somehow developed a unique set of digestive enzymes to deal with the oils in the wood that tend to inhibit fungi.

The reason James and I are extremely interested in pine loving oysters is because the Rocky Mountains are plagued with a pine eating beetle that is destroying our forests by the entire mountainside. The general way to deal with this problem (due to the extreme fire danger it creates) is to cut down the infected trees and pile them in large piles. They are used mainly for fire wood, but the pine loving  mushrooms would decompose the wood much faster, creating larger soil depth. Paul Stamets has a discussion in his book, Mycelium Running, about the honey mushroom and its method of creating a deeper humus depth. Many of these plagues, whether they be a fungus or an insect, may look very disastrous to the environment to humans. This is only because of our perception of time. The trees that once stood as a forest are now decomposing, increasing the potential of the forest to create more life. As soil depth increases, the forest can house more and more plants. We would like to make these Pleurotus part of the solution to this large problem we are facing today.

Now that we have received our spring rains, the Colorado mushroom season has begun. I have seen quite a few Coprinus comatus around the city, but if you look in your local riparian areas you may come across the infamous oyster mushroom, Pleurotus pulmonarius in most cases, growing on dead or dying deciduous trees and stumps. Pleutotus pulmonarius is the most common species in lower elevations, favoring cottonwood trees. Colorado also has a couple other species, Pleurotus populinus probably being the next most well known. It is found growing on aspen and has more delicate ‘shelves’. Another species, Pleurotus dryinus has also been found in Colorado. It is usually has less of a clustering habit, longer and larger stems, a mostly centrally attached stem and a very distinctive cap. All oyster mushrooms have a very distinctive shape, sometimes growing in fans that are shaped closely to an oyster shell. They also are known to have a slight shellfish odor, making the common name ‘oyster mushroom’ very fitting.
To make sure you have a Pleurotus species take a spore print. Put a mature mushroom cap on a piece of white paper and with your finger, moisten the cap with a little bit of water. Then put a glass over top of it to reduce air flow around the cap so the spores fall off of the gills and onto the paper. Leave it over night until the next morning. You should be left with a gray or gray/lilac spore print.
James and I have been finding quite a few oysters out already, as the weather is permitting them to fruit. They are just beginning as most of the logs we know have large amounts of mushrooms have yet to show major signs of fruiting. Nonetheless, there are still pounds of mushrooms already out and ready for picking!
Below is a gallery featuring some of the oyster mushrooms we have found in the past few days. Bert, the newest member of Amateur Mycology is shown above with a particularly large cluster of Pleurotus pulmonarius I found on a cottonwood stump yesterday in Boulder. He brought us to a couple other oyster mushroom spots as that were very interesting! Stay tuned for an Amateur Mycology Video Magazine episode featuring our early oyster hunts!
P.S. No morels seen yet, but we will keep you posted. Still to early.

While driving through Littleton, Colorado James and I came across a park that had many different species of mushrooms growing in it. What first got our attention was large fruiting of Agaricus in the area, and as we were working on the Colorado Agaricus Project, this park was an interesting find. Unfortunately for us, most of the Agaricus found in the area were the yellow staining, foul smelling and poisonous Agaricus xanthodermus (the bane of most Agaricus hunter’s existence) and the giant mushroom of culinary disappointment, Agaricus bernardii. However, in one corner of the park, a cottonwood stump had been chopped to just above ground level. This stump had Oyster Mushrooms (Pleurotus pulmonarius) growing out one side, and Velvet Foot Mushrooms (Flammulina velutipes) out the other! Luckily for the Amateur Mycologists, we are able to culture these fungi in sterile lab conditions, as well as establishing them on cardboard for a more ‘natural’ form of storing the mycelium, making them the newest members of the Amateur Mycology Culture Library. Remember… the Amateur Mycology Culture Library page has an updated list of species in cold storage, and make sure you check back soon to see a full explanation of cardboard/stembutt culture from the exact oyster mushroom cluster pictured above!