“Can you eat them?” is the question I’m inevitably asked when we find dense mats of mushrooms growing up from our wood chip mulch after a good rain.
And while these ones look quite showy and fleshy, you’d easily walk by them without a second glance.
Each mushroom is no more than the size of a pinky nail, just a few millimeters wide and tall. In their immature state, the mushrooms are inconspicuous nubs with spiky or fluted sides, fully enclosed to protect the “eggs” inside.
As they age, the caps rupture to reveal a nest of eggs denotive of the mushrooms’ common name: bird’s nest fungi.
What is bird’s nest fungus?
Bird’s nest fungus — the mushroom — is not the same bird’s nest in Chinese bird’s nest soup (which are actual birds’ nests from the edible-nest swiftlet and black-nest swiftlet).
Bird’s nest fungi are part of the Nidulariaceae family of fungi, known for their stemless, rounded, hollow fruitbodies that resemble egg-filled birds’ nests. They include Nidularia, Nidula, Mycocalia, Crucibulum, and Cyathus.
The fungi that show up most frequently in my garden are Cyathus striatus, which have flared, tan-colored cups (called sporocarp) holding flattened, dark gray “eggs” (called periodoles) that are shaped like lentils.
They are excellent decomposers and thrive in damp, woodsy environments, often appearing in shady vegetable gardens or woody mulched paths. As long as the climate is temperate with intermittent rains, bird’s nest fungi can spread through any decaying organic matter they come in contact with.
You’ll find groups of bird’s nest fungi in dead tree trunks, rotted timber, wood mulch, bark chips, sawdust, decaying vegetation, or humus-rich soil, especially in fall. You’ll even see them pop up in animal dung, as the periodoles can survive a journey through the digestive tracts of cows and horses.
The life cycle of bird’s nest fungus
Bird’s nest fungi are not only fascinating in appearance, but fascinating in their reproductive strategy. They multiply through the “eggs” in their cups, but not in the way you might think.
Up close, the eggs are almost metallic looking, resembling shiny river stones. They’re known as periodoles, and they serve as protective sacs for the mushroom’s spores.
When drops of water from rain or irrigation land in the cups, they eject the periodoles up to four feet away — hopefully to hospitable terrain where they can reproduce.
At the scale of several millimeters, even a single raindrop can exert enough force to launch the periodoles like a water cannon. This unique method of dispersal is why you’ll sometimes hear bird’s nest fungi referred to as “splash cups.”
This is where it gets really interesting: Each periodole is connected to a funicular cord, essentially a long, fine thread with a sticky tail that unwinds several inches. Yes, inches. From that tiny cup!
As the periodole sails through the air, the cord may come in contact with, say, a blade of grass or a twig. It gets caught by its tail and rapidly wraps around the grass, much like a high-flying game of tetherball.
Here it remains until the periodole dries, then splits open to release the spores.
When the spores germinate, they grow into branching filaments called hyphae. The mass of hyphae (called mycelium) weaves through moist woody debris and consumes the wood to fuel its growth.
Bird’s nest fungi are saprophytes (microorganisms that live on dead organic matter) and this natural process is largely how wood decomposes.
When two different mating strains of mycelia fuse together, they form a new bird’s nest fungus that takes nutrients from organic waste and breaks it down rapidly (speeding up decomposition by two-fold.) This cycle usually occurs between July and October.
Having bird’s nest fungi in the garden makes it much easier and quicker to clean up plant debris, since they reduce large chunks into slivers that eventually decay and help enrich the soil.
Is bird’s nest fungus edible?
At a span of just a centimeter across, bird’s nest fungi are considered inedible due to their tiny size, though no study has ever shown them to be poisonous.
Harold J. Brodie, a Canadian mycologist who studied bird’s nest fungi extensively, concluded in his 1975 book, The Bird’s Nest Fungi, that the mushrooms were “not sufficiently large, fleshy, or odorous to be of interest to humans as food,” though some species have been used by native peoples to stimulate fertility.
The 1910 publication Minnesota Plant Studies suggests they are “not edible owing to their leathery texture.”
So we’ll give this species a miss, as there are far more satisfying (and delicious) mushrooms you can harvest in the wild.
How do you get rid of bird’s nest fungus?
Of all the fungi present in a garden, bird’s nest fungus is one of the most beneficial because of its natural composting abilities. It isn’t harmful to humans, dogs, wildlife, or living plants, so control measures aren’t necessary.
But if the “eggs” become a nuisance (sticking to surfaces like cars, houses, or other structures where they’re difficult to remove), you can lessen the chances of bird’s nest fungi appearing in your yard by raking the soil frequently, decreasing irrigation in shady areas, and using living mulches and edible ground covers (instead of arborist wood chips) in your garden beds.
Fungicide should never be used, as it could disrupt the natural processes in your ecosystem.
This post updated from an article that originally appeared on January 15, 2015.