Why are mushrooms popping up in my yard?

By Georgianne Messina

Note:
This article will not identify poisonous versus edible fungi. Identification of mushrooms should be done by experts -UC Master Gardeners are not mycologists either professionally or as hobbyists. Mis-identification of mushrooms has had lethal effects on humans and pets.

This winter, there seems to be no avoidance in spotting a multitude of mushrooms growing in yards, park trails, and occasionally in houseplants. Are we being invaded by UFOs (unidentified fungal objects) more than last year? It seems like it. Why? Are these mushrooms harmful to people and pets? Should I get rid of them and how can I dispose of them in a safe manner?

Why are there so many mushrooms this year?

Alameda County, along with the rest of Northern California welcomed the abundance of rain that fell this season (2021-2022). No sooner did one bout of rainfall stop, another began. The ground is still moist from all the rain. The moist, damp soil combined with decaying organic matter is an ideal environment for fungal growth. Mushrooms are the fruiting bodies of airborne spores that have found their happy place in your soil. “Fungal fruiting structures release tiny spores that are easily carried on air currents to new sites. When spores reach a favorable place to grow, they germinate and send out long thin filaments called hyphae”. Hyphae (not visible to the human eye) are the building blocks of the fungus, but when you see it in a clump, this is referred to as mycelia (visible threadlike network of hyphae). Perhaps you have seen these networks forming on a decaying root system of a plant, in a compost pile, or even in a mulched area in your yard.

Mushrooms – good or bad?

The appearance of mushrooms in a garden or yard brings anxiety to many. Though wild mushrooms can be harmful, if ingested, they also are essential supporters of plants such as native oaks, pines, and conifers. They may serve as indicators of plant or soil health.

Are Mushrooms Beneficial?

While mushrooms are beneficial for many reasons, we will focus on just two in this blog. Please note that mushrooms and fungi will be used interchangeably.

1. 

   Photo submitted to our Help Desk-Author photo (Palomares Hills) – mushrooms on decaying birch roots
   Mushrooms aid in the decomposition of matter. They secrete enzymes that begin the process of decomposition. In fact, they sprout up in soils that are rich in organic matter – indicating healthy soil. You will see mushrooms in all sorts of decaying materials … compost, decaying tree roots, leaf litter, old wood, especially when moisture/dampness is present. Mushrooms are often seen at the base of a tree and can indicate that the tree is not doing well. Those mushrooms are likely a common species found in our area, the Armillaria (often called honey fungus), one of the largest living organisms in the world. It is a parasitic fungus that feeds on living and dead plant material.
2. 

   R Photo:Jerrold Turney, Los Angeles County; Dept. of Agricultural Commissioner L Photo: adeleon (Palomares Hills)
   The relationship between fungi and mycorrhizae are critical to the optimal growth of plants. Fungal hyphae and plant roots working together are called mycorrhizae. Mycorrhizae in the soil has been found to suppress soil-borne pathogens and protect plants from root diseases.

Are Mushrooms Harmful?

Despite the beneficial attributes of fungi to your soil and plants, they are often harmful to humans and pets when eaten. Several varieties of mushrooms are toxic, but very few are actually deadly
This article will not identify poisonous versus edible. Identification of mushrooms should be done by expert mycologists. UCCE Master Gardeners are not mycologists either professionally or as hobbyists. The misidentification of mushrooms has had lethal effects on humans and pets.

As East Bay Regional Parks (EBRP) website points out: “The Bay Area is home to two of the world's most toxic mushrooms. Amanita phalloides (the Death Cap) and Amanita ocreata (the Western Destroying Angel). Both are robust, handsome mushrooms that grow near oak trees, and both contain lethal toxins.” The article goes on to say that these two mushroom species are responsible for most of the mushroom poisonings; however, Galerina and Lepiota species are poisonous as well and are found in the Bay Area."

Text and photos by Trent Pearce, Naturalist, Tilden Nature Area
More photos can be found on the EBRP website.
Erring on the side of caution seems to be the best way to approach an unidentified, wild mushroom.

How do I safely remove and dispose of a UFO (unidentified fungal object)?

To remove the mushrooms, carefully rake them up in a small pile or dislodge them manually (wear nitrile gloves). Place the mushrooms in a paper or compostable bag and place it in the green bin. Discard the gloves, wash your hands after this activity, keep pets and children away from the area while you are working. Again, best to err on the side of caution since you do not know the type of mushroom you are dealing with.

Are Mushrooms Harmful to Children?

Wild mushrooms certainly have the potential to be harmful. From November 2016 through January 2018, there were about 1038 cases of mushroom poisoning in California Of those cases, 433 (41.7%) were children under six years of age*. Eating poisonous mushrooms can cause abdominal pain, cramping, vomiting, diarrhea, liver damage, or death. Anyone who develops symptoms after eating wild mushrooms should seek immediate medical attention. People who develop these symptoms should immediately contact the California Poison Control System at (800) 222-1222 or their health care provider

Are Mushrooms Harmful to Pets?

Again, wild mushrooms DO have the potential to be harmful to pets. Dogs are affected differently than cats. Some mushrooms have a fishy odor which attracts pets.

According to the UC Davis School of Veterinary Medicine,” It is safest to assume that all wild mushrooms that your dog encounters are toxic.“ If your pet may have been poisoned by mushrooms, try to get a sample of the same mushroom or mushrooms from where they were found. This will help aid in identification.

Place any available material in a paper bag or waxed paper, not plastic, and refrigerate until it can be examined. Note where the mushrooms were collected in case the mushrooms may have been contaminated by uptake of pesticides or heavy metals from lawns, roadsides, or industrial areas.
Symptoms are delayed after ingestion (up to 12+hours). Do not wait for the mushroom to be identified or wait for symptoms to start - call your veterinarian or contact an emergency veterinary hospital as rapid treatment is critical.

Resources:

Why are mushroom growing in my lawn?

UC IPM Pest Note: Ammilaria Root Rot

UC IPM Wood Decay Fungi in Landscape Trees

Mushroom Toxicity in Dogs

More resources:

Mushrooms in lawns  

http://ipm.ucanr.edu/PMG/PESTNOTES/pn74100.html

Armillaria Root Rot Management

Armillaria Root Rot Management Guidelines--UC IPM

https://ucanr.edu/blogs/uccemgsantaclaranews/index.cfm?tagname=Mushrooms

* California Department of Public Health - Urges Caution When Collecting Wild Mushrooms

https://www.cdph.ca.gov/Programs/OPA/Pages/NR18-007.aspx

East Bay Regional Parks - Toxic Mushrooms

https://www.ebparks.org/safety/trails/toxic-mushrooms

California Poison Control System

https://calpoison.org/about-wild-mushrooms#:~:text=The%20most%20serious%20illnesses%20and,prevent%20exposure%20to%20wild%20mushrooms.

Stanislaus County Master Gardeners - Magical Mushrooms

https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=51028

Mycological Society of San Francisco

https://www.mssf.org/

Toxic Fungi of North America

https://www.mykoweb.com/TFWNA/Toxic_Fungi_of_Western_NA.pdf

Mushroom Poisoning in Dogs

https://www.aspcapro.org/resource/mushroom-poisoning-dogs

https://namyco.org/mushroom_poisonings_in_dogs_an.php

Want to learn more?

This blog post is brought to you by the Help Desk of the UC Master Gardeners of Alameda County.  Subscribe to our blog!

Have a gardening question? We'll help. You can reach us by:

• Emailing acmg@ucanr.edu. Please include a photo of the problem, if you can, plus your name, phone number, city and a description of the problem.
• Using our online form.
• By phone, during our office hours, 10 am to noon Wednesday and 11 am to 1 pm Thursday: 510-670-5645. At other times, please leave a message and we'll return your call during our office hours.
• In person at our Hayward office, during our office hours, only by appointment.