By Bruce Wenning
Every fall I get questions from people who are worried about the appearance of mushrooms (toadstools) growing in their lawns and gardens. Some people feel that they are unsightly and sure that their presence indicates that something is wrong. Others welcome these fungi and are delighted when they learn that mushrooms serve an ecological purpose by helping in the decomposition of soil organic matter. Only one caller has mentioned that the mushrooms growing in her garden and lawn added interest as "colorful little plants."
Mushrooms are fungi. Green plants (trees, shrubs, lawns and garden plants) contain chlorophyll in their leaves, and, by the action of photosynthesis, produce sugars and other compounds from carbon dioxide and water. Mushrooms, on the other hand lack chlorophyll and cannot undergo photosynthesis. They must derive their nutrients from dead plant and animal matter.
How do they do this? Mushrooms colonize organic debris in the soil by hyphae (fine branching tubes). As their hyphae grow and "seek out" organic debris such as buried wood chips, dead roots, pieces of wood, lawn thatch, etc., they gain more mass by branching outward and fusing together forming a larger structure called a mycelium. Mycelium is the body of the fungus and hyphae are its individual components.
As the mycelium moves or grows through the soil by way of multiple growing points, it increases in size as a diffuse, loosely combined fungal mass-producing various enzymes and other chemicals to digest or feed on organic compounds in the soil. Mushrooms and other decomposing fungi are important garden organisms involved with organic matter break down and nutrient recycling. They are welcomed additions to the organically-tended lawn and garden.
Mushrooms are the above ground portion of the underground growing mycelium. Mushrooms are the actual fruiting body or reproductive structure of the fungus. They are the "tip of the iceberg" of the entire fungus. In general, a mushroom is composed of a cap, gills, ring, stalk, cup and root-like extensions (rhizomorphs). Under the cap, spores are produced in the gills for release into the air. Boletes mushrooms release spores from pores instead of gills.
Spores, when released, can be carried by wind, rain, irrigation water from sprinklers, animals, insects and gardening tools that come into contact with the mushroom. For a spore to germinate into hyphae, the right combination of moisture, temperature, and available organic compounds must be present for growth and eventual development to occur. The process from spore to hyphae to a mycelium that produces a mushroom could take weeks to years depending upon the fungal species and environmental conditions.
Fairy rings are groups of mushrooms growing in lawns and pastures that form circular or semi-circular patterns. These mushroom rings occur during spring and fall in all types of grasses when temperatures range between 45 and 65 degrees F. Many species of mushrooms can form fairy rings, however these three species are the most common; Marasmius oreades (small, tan color), Agaricus campestris (edible, sold in grocery stores), and Chlorophyllum molybdites (large, white poisonous).
Fairy rings can vary from a few inches to more than 50 feet in length. The mycelium producing the fairy ring mushrooms can be as deep as eight inches or more, impeding water from reaching turfgrass roots. This is the reason why fairy ring fungi are considered a disease in lawns. Grass is killed inside the ring of mushrooms and grass. The outer ring of mushrooms and grass is alive with the grass exhibiting deep green color and a faster growth rate. This is due to the mushrooms' decomposing soil organic matter and releasing nutrients to the grass as a natural fertilizer. It is not unusual for a fairy ring to resemble a bulls eye appearance similar to dog urine spots on a lawn. However, dog urine spots lack mushrooms.
Fairy rings spread outward from a few inches to several feet per year. According to Mass Audubon naturalist, Dan McCullough, if the fairy ring mycelium hits a rock, fence post, bird feeder post or some other impeding object, the ring will become interrupted, possibly loosing its circular or semi-circular pattern. Digging out the mushroom-mycelium mass and replacing with good topsoil will help eliminate this problem.
McCullough owns fourteen mushroom field guides and still has problems identifying certain species. He strongly urges the beginner to use caution when looking for edible mushrooms. Identifying mushrooms is not like identifying birds, where one bird guide may cover all the birds in an area. You must use several guides when trying to identify mushrooms and it is strongly advisable to take a class to sharpen your skills.
While this summer was filled with warm, sunny days that encouraged recreation on the Charles River and in its parklands, it also saw an explosive growth of a potentially harmful algae in the Lower Charles. First identified in early August, the fluorescent green algal bloom extended from the Harvard/Massachusetts Avenue Bridge east to the Museum of Science, with dense, floating mats of algae most visible in lagoons, canals and along the river’s edge in Boston and Cambridge.