Do Mushrooms Need Sunlight?

Mushrooms are fungi, a group of organisms that also includes yeasts, molds, and mildews—species that can thrive in shadow and the forgotten corners of your pantry. And while many fungi actually live in sunny spots, they don’t need light in the same way that plants do. Unlike plants, fungi don’t photosynthesize—they don’t use chlorophyll to convert light into chemical energy. Light, then, isn’t their primary source of food or energy. So what is a mushroom’s source of energy? Generally, the answer is organic matter. Mushrooms are heterotrophs, meaning they get their nutrients from other organisms instead of producing their own food. In this way, mushrooms are one step up the food chain from plants. Mushrooms secure their food by secreting enzymes into the surface they’re growing on, whether that’s a tree or the forest floor or elsewhere. The enzymes digest the food, which is then absorbed through the cell walls. What is food for a mushroom? That depends. Most mushrooms are saprotrophic: they eat dead organic material, such as fallen tree branches or leaves. Some, though, are parasitic: they eat living organisms, such as growing plants. Saprotrophic fungi are largely responsible for the decomposition of organic matter. They break down dead plants and animals, converting their food into nutrients that are then released into the soil—which supports the growth of plants, which might later be eaten by fungi, starting the cycle all over again. Though mushrooms don’t use sunlight like plants do, light can still be useful for some fungi. Light triggers some types of mushrooms to grow long stems and produce larger fruit, or mushroom caps. Species that might be helped along by some light include shiitake, oyster, and white button mushrooms all edible varieties you might find on your dinner table.