The fungi kingdom might hold some of the answers for combating climate change. But these answers won’t be found in what you picture when you think of a typical mushroom. Instead, they lie within part of the fungi that are invisible to our daily awareness. Mushrooms have an intricate root system called mycelium that provides the mushroom body with nutrients. Mycelium also cleanses the surrounding soil of toxins while working to decompose dead plant and animal matter. And importantly, these root systems can actually exist apart from a mushroom body. This type of fungi is called mycorrhizal fungi. Scientists are hoping to unlock answers to solving the climate crisis within this category of fungi. Mycorrhizal fungi exist entirely underground and survive by clinging to the root systems of other plants. They form a symbiotic relationship with the plants, in which the mycorrhizal fungi release enzymes to break down dead matter and convert it into nutrients within the soil for plants to consume. These root systems are extremely complex, and their total length in the top 10cm of the soil reaches more than 280 quadrillion miles globally. So how does this help with global warming? Mycorrhizal fungi need carbon dioxide (CO2) to survive. People may think that trees in forest ecosystems do all of the work to absorb CO2, but it is actually fungi that hold down the fort. Mycorrhizal fungi keep CO2 locked in their system to aid in the decaying process. This prevents CO2 from trapping heat in our atmosphere, making mycorrhizal fungi networks one of the earth’s largest carbon sinks. Plants are estimated to transfer 5 billion tons of carbon to mycorrhizal fungi every year. Unfortunately, with increasing forest degradation comes the destruction of mycorrhizal fungi. More and more plant matter is being cleared from construction and agricultural sites. Supporting decomposition by allowing plant materials to decay instead of removing them helps conserve the fungi in the soil. Preserving these systems, instead of removing them, is becoming more crucial by the day. However, there is still room for hope. Efforts to fight deforestation paired with regenerative agriculture provide space for soil restoration by allowing mycorrhizal fungi to thrive.

It’s often said that you can tell how edible a mushroom is by the number of names it has. This concept certainly applies to the edible Flammulina velutipes, which goes by the common names Enokitake (and the shortened form Enoki), Velvet Foot, Winter Mushroom, and Golden Mushroom, as well as many other derivatives and regional names (if you’re outside the United States, you probably call it something else!). Another reason the species has so many names is because it looks very different in the wild than it does in the grocery store: in the wild, it grows as an orange umbrella-shaped mushroom with a black fuzzy stipe, but when cultivated it grows as a pale thin needle-shaped (or perhaps spaghetti-shaped) mushroom with a tiny pileus. I generally use the names F. velutipes, Velvet Foot, and Enoki, since each one emphasizes a different physical aspect of the mushroom. Description Natural Form The Velvet Foot is an umbrella-shaped agaric that grows from dead hardwood in clusters that share a common base. Individually, these are small to medium-sized mushrooms, growing 1-7 cm across and 2-11 cm tall. The whole cluster, however, can get much larger – perhaps a foot or more – although I’ve never been lucky enough to find that many at one time. When fresh, the pileus of F. velutipes is smooth but covered in a thin layer of slime, which makes it slippery to tacky (when dried out a bit). The cap is typically orangish with a lighter margin, although it can vary from reddish brown to bright orange to yellow-brown. Underneath the cap, the Velvet Foot sports whitish to yellowish gills that are attached to the central stipe. The gills form close together and usually dip slightly before they connect to the stipe. Flammulina velutipes spores are white, so the mushroom will give you a white spore print. The Velvet Foot’s namesake is its stipe, which is also its most distinctive – and beautiful – feature. When young, the stipe is yellowish or orangish and covered in tiny white hairs. As it matures, the stipe darkens to dark brown and develops a velvety texture (similar to the surface of a peach), progressing from the base upward. When fully mature, only the very tip of the stipe remains lighter and smooth, staying about the same color as the adjacent gills. Cultivated Form The cultivated form of F. velutipes is so dramatically different from the wild form that it has inspired many common names: Enokitake, Golden Needle, Futu, Lily Mushrooms, etc. The name Golden Needle is particularly apt: the cultivated mushrooms are mostly stipe, topped by a tiny pileus scarcely wider than the stipe. The colors are much paler than the normal form and range from white to light yellow. The largest cultivated enoki mushrooms measure roughly 30 cm long and 3 cm wide at the pileus, although dimensions are highly variable based on when the mushrooms were harvested. You actually find the cultivated form in the wild, whenever the mushrooms begin growing underneath bark. The purpose of a mushroom is to release spores into the air, but a mushroom trapped underneath bark cannot accomplish this task because it has no access to the air currents. The cultivated form of F. velutipes is really just a clever solution to this problem. First, the mushroom senses it is trapped under bark by measuring the amount of light and carbon dioxide. Bark blocks light and traps CO2 (like us, fungi breathe out CO2 as they grow, which leaves the wood and gets stuck below the bark), so the mushroom can tell if the environment is unfavorable when there is very little light and a very high CO2 concentration. Under these conditions, the fungus switches to growing in the cultivated form. Instead of devoting resources to expanding the cap, developing color, and producing spores, the mushrooms instead put all their energy into growing tall. This results in long thin pale mushrooms. As the cultivated form mushrooms extend, they search for any cracks in the bark (places where light gets in and there is less carbon dioxide). Once they encounter a crack, they grow through the gap and escape into the external environment. Upon encountering open air, the mushrooms switch back to growing in the natural form: the pileus expands and develops color and the stipe becomes black and fuzzy. This process ensures the mushroom doesn’t waste energy on spore production until it is sure the spores can be successfully deposited into air currents. The next time you find some Velvet Foot, peel back the nearby bark to see if you can find the cultivated forms as well! Unfortunately, I haven’t been lucky enough to document this phenomenon, but there are some great photos of it on the websites linked under “See Further.” Humans decided that the cultivated form is better for cooking, so we intentionally grow the mushrooms under conditions that mimic bark. This process is explained further under the “Cultivation” section, below. Ecology In the wild, F. velutipes can be found decomposing hardwood logs, usually with the bark still attached. Its fruiting season starts in fall and continues throughout the winter, which earned it the common name Winter Mushroom. However, you occasionally find the Velvet Foot at other times of year as well. It particularly likes warm spells in the winter and cold snaps during other seasons (whenever temperatures drop below 60°F for long enough to initiate fruiting). The mushrooms decompose various kinds of hardwood and will sometimes grow from roots or buried wood and may therefore appear to be growing terrestrially. The Velvet Foot seems to have a particular affinity for elms, so it is especially common in places recently impacted by a wave of Dutch Elm Disease. Other Flammulina Species Currently, there are 11 recognized species of Flammulina, but it seems likely there are at least two more hiding in Asia. All species in the genus have the distinctive black velvety stipe, making it easy to get to genus. Distinguishing the species, however, is best done with a microscope. Fortunately, you can get pretty close by looking at the pileus and checking the habitat. In North America, there are five Flammulina species you have to consider. If the species is growing on poplar or aspen