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Fall Fungus Among Us

Some of the most curious fungi appear in the fall. With names like stinkhorns, puffballs, bird’s nests, and even jack-o'-lanterns, all are interesting; many are intriguing.

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Updated:

September 19, 2023

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Figure 1. Fairy ring by William M. Brown Jr. on Bugwood.org. CC BY

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A warm and wet autumn is the ideal time for the fungus among us to appear. This natural occurrence may seem unsettling. Many people notice mushrooms popping up in the lawns and landscapes. When mushrooms, also known as toadstools, appear in a circle or arc, it is commonly called a fairy ring. Over fifty species of mushrooms in the class Basidiomycetes can grow in a circle. According to folklore, this is where fairies danced in a circle. Often, there is a slight discoloration of the turfgrasses near the fairy rings. Over the years, the rings of toadstools widen and may overlap, perhaps as the fairy population increases. I look forward to seeing them appear in my backyard each year.

Puffball and mature puffball — Figure 2. (Left) Puffball (*Lycoperdon pyriforme*) by Joseph OBrien, USDA Forest Service on Bugwood.org. CC BY and (Right) Mature puffballs by Mandy L. Smith, Penn State

Puffballs start small, perhaps the size of a marble, and can become as large as a baseball, softball, or basketball, depending upon the species. The giant puffball (Calvatia gigantea) can reach the size of a bushel basket! Unlike mushrooms, puffballs may have a short, wide stalk. The ones on my lawn look like white, leathery golf balls. They seem to appear overnight. I patiently wait for them to mature, and then I step on them to see the plume of brown spore-filled “smoke” puff into the air, helping establish the next generation of puffballs.

Bird’s nest fungi (Crucibulum spp. and Cyanthus spp.) resemble miniature birds’ nests with tiny eggs! A large nest might be one-half-inch in diameter. These are common in wood mulch, but I’ve found them on cones under white spruce trees. No stalks grow on these fungi. The spores are released from the mature “eggs.” Children, as well as curious adults, find these harmless little fungi adorable.

Figure 4. Dog stinkhorn (*Mutinus caninus*) by Chris Evans, University of Illinois on Bugwood.org. CC BY-NC

Stinkhorns (family Phallaceae) emerge from witch’s eggs, especially in mulched landscape beds. The half-buried, elongated ping-pong balls open to release orange-red finger-like stalks that are four to six inches tall. The stalks are topped with narrow caps of brownish-green slime. The caps smell awful! This putrid smell attracts flies that land and then carry off spores to germinate in other locations. The good news is that stinkhorns are very short-lived. While striking at first, within a day or two, they collapse and vanish entirely in a week.

Jack-O\'-Lantern mushroom — Figure 5. Jack-O'-Lantern mushroom (*Omphalotus illudens*) by Stephanie M. Adams, The Morton Arboretum on Bugwood.org. CC BY-NC

The Jack-O'-Lanterns (Omphalotus illudens, formerly Clitocybe illudens) are among the most exciting mushrooms. These pumpkin-colored beauties grow at the base of stumps or living oak trees. Each cluster may contain 15 to 20 mushrooms with caps up to four inches in diameter. Search for them during the day and mark the area with a reflective ribbon. Return on a moonless evening and sit patiently until your eyes become accustomed to the dark. Then, lie on the ground and look toward the gills on the underside of the caps. They glow greenish-blue with bioluminescent light! It is one of the most curious effects I have ever seen!

These fungi are all saprophytes. They break down organic matter to absorb nutrients from it. Importantly, they do not cause disease in live plants, so there is no danger to your lawn or landscape plants. No treatment or fungicide will manage saprophytes in our lawns or gardens. Herbicides (weed-killers) don’t work on fungi. Fungicides do not manage these saprophytes. Fungicides prevent disease-causing fungal spores from establishing on a green plant’s living tissue. Fungi are natural recyclers of decaying wood and organic matter in the soil. They are part of the clean-up crew in our environment.

The main portion of a saprophytic fungus remains underground. The mycelium is made of delicate, white, hair-like structures that spread extensively throughout the organic matter or soil. The part that we see is called the fruiting body. It appears above the surface to distribute spores and to intrigue us. If you are concerned about their presence, the best strategy is to remove the fruiting body with a gloved hand or a trowel and drop it into the trash as soon as it appears. Teach children that mushrooms are interesting and fun to look at, but they should never be touched or eaten unless they come from the grocery store.

Penn State Extension does not permit its Master Gardeners to identify mushrooms or other saprophytic fungi as the chance of misidentification is too great. While most fungi are benign (edible or inedible), a few are poisonous. Use printed field guides, online resources, and well-experienced mushroom club members to guide the curious toward identification.