Slime molds are unsightly but harmless visitors
A word of caution: Unless you share my fondness for fungi and decomposers, you might want to wait to read this until after breakfast!
Now that you have been warned, the yellow or white blob growing in the mulch in your backyard is not the regurgitation of the neighbor’s cat or dog. The brightly colored pile is a slime mold that is feeding on decomposing plant material, fungi and bacteria, and it will disappear with warmer weather.
If the idea of growing something accurately named as the dog vomit slime mold is too much for you, simply remove the offensive organism with a shovel. You could also try calling it by one of its other common names, including scrambled egg slime mold, yellow blob slime mold and regurgitated cat breakfast slime mold.
Scientifically speaking, Fuligo septica is an interesting primitive organism. Wet weather and increasing temperatures trigger growth that first appears a bit slimy. This early stage is when the slime mold is typically a vivid yellow or orange. With age (a few days) the mass begins to dry and fade into a less-noticeable white or tan. Eventually, the blob will turn gray and powdery and disappear back into the mulch.
The dog vomit slime mold also appears occasionally in turfgrass. Use a strong spray of water to dislodge the blob and disperse the spores if it is intolerable on the lawn.
Two other interesting decomposers that often appear in late spring are bird’s nest fungus and artillery fungus.
Bird’s nest fungi are named for their cuplike shape. Individual “nests” are very small (up to one-quarter inch in diameter) but appear in masses. Look closely if you observe this fungus in your garden; the tiny “nests” also contain tiny “eggs.” As water splashes into the cuplike structure of the fungi, the “eggs” are splashed out and dispersed to start new colonies.
Like the slime molds, bird’s nest fungi feed on decomposing plant material and are very seasonal. If you find them growing in your mulch, share this little wonder with a child.
If artillery fungi find their way to your mulch, you might not detect the actual fungus, but you will see their black, sticky spore masses. The fruiting body of the artillery fungus is shaped similarly to the bird’s nest fungus but is only about one-tenth of an inch in diameter.
The artillery fungus gets its name because of its ability to invert the cuplike fruiting body and shoot spore packets as far as 20 feet away. The fungus has the ability to orient itself toward light-colored structures, making your white house or car a primary target. The first time I saw this in Lawrence, the spots were not on the house itself but on the white gutters, the concrete steps and the light-colored wooden shelf on the barbecue grill.
Spore packets of the artillery fungus are sticky and difficult to remove. If you suspect artillery fungus in your yard, your best bet is to remove the mulch from your plantings and replace with fresh mulch. This is one instance when inorganic mulch, like gravel or stone, might be beneficial.
— Jennifer Smith is the Douglas County Extension Agent-Horticulture for K-State Research and Extension. Contact her or an Extension Master Gardener with your gardening questions at 843-7058 or firstname.lastname@example.org.