On Dec. 8 The Sacramento Bee ran a story on the death of an 8-week old puppy from poisoning by ingesting a “death cap” mushroom (Amanita phalloides) growing in its owners’ lawn. Amanita phalloides can be found anywhere that oak trees, especially live oaks, grow. Last year’s wet winter has caused a burst of mushroom growth this fall and early winter, even though rainfall has been light and soils are mostly dry. Mushroom identification is best left to expert mycologists. Several types of less lethal mushrooms or fungal puff balls are more commonly found in our gardens than the “death cap” type, but common sense dictates that great care be taken to protect pets and humans by attempting to control for mushroom growth in the urban landscape. Immediately call your vet or doctor if you suspect that any type of mushroom may have been eaten by pets or children.
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“Fairy ring” mushrooms grow in turfgrass. The mushrooms grow in rings or circles that can be a few inches or many feet wide. The superficial type of fairy ring mushrooms grow in thatch (a layer of dead grass) and in decomposing organic matter (leaves, small twigs, etc.). The center of the circle is often depressed and surrounded by a dark green ring of grass. The fungi that produce the non-superficial type of fairy ring mushroom grow in the soil. The center of the circle has a hard surface that prevents water penetration so that the grass in the center dies.
Removing thatch and litter will help eliminate the superficial type of fairy ring mushroom. Removing the soil and any decaying organic matter including dead tree roots and old lumber scraps (often found in subdivisions where left over construction materials have been covered over with top soil) will reduce the food source for non-superficial fairy ring mushrooms. Well-fed and properly irrigated lawns have fewer problems with mushrooms.
Most of the mushrooms growing in fairy rings are not considered to be poisonous, but just in case – rake out the mushrooms or mow them down and wear rubber gloves when picking them up to dispose of them in the trash, not the compost bin.
Here in the Central Valley, many tree and other plant species suffer from armillaria root rot (Armillaria mellea): infected plants produce mushrooms that are associated with the disease. In our dry climate, root rot is mostly caused by overwatering and the disease can be lethal to the tree or plant.
The honey-colored mushrooms that grow in clusters on the bark or lower trunk of the trees appear (briefly) from October to February in California. Avoid overwatering trees that have become adapted to our arid hot climate and eliminate any insect pests that may stress plants. Treatment with topical fungicides has limited success in controlling the disease and soil fumigation can damage or kill neighboring plants. Remove honey mushrooms carefully and dispose of them.
A few weeks ago, a reader sent a photo of the weirdest-looking puffball fungus with a young lettuce plant growing on top of it. He’d added topsoil purchased at a big box garden center to his planting bed and it’s likely that the topsoil had not been thoroughly sterilized or screened. Since we have no idea of what could have been in the soil (chemicals, organic matter) and what type of puffball this was, I advised replacing all the soil and against eating any of the vegetables.
Send Elinor Teague plant questions at firstname.lastname@example.org.