Woodchips are a popular mulch for many; it’s long-lasting, helps to keep weeds out, and it gives gardens a tidy appearance. But under certain conditions, wood mulch can be the breeding ground for some rather weird stuff. For instance, after an extended rainy spell you may find among your perennials a yellowish mass of, well…something.
This would be Fuligo septica, more commonly known as dog vomit slime mold or scrambled eggs slime, which gives you an idea of its appearance. Slime molds - a sort of catch-all term to encompass a group of some 900 species that are not closely related to one another even though they share some traits - are fascinating, if not particularly photogenic. They’re not fungi, though they reproduce by spores, and they’re not animals, though they can move several feet per day. F. septica actually starts out as a collection of single-celled, but when conditions are right they swarm together to form a plasmodium, essentially a giant cell with one membrane but thousands of nuclei. This plasmodium may even lurch over your flower beds like something out of The Blob, feeding on the bacteria it encounters on mulch. Fortunately, though, it only looks for microscopic-scale victims; after this short feeding phase the plasmodium disperses into its reproductive phase and vanishes.
People will call in from time to time in the summer to report that the sides of their house, or their car, is peppered with tiny black spots, and that no amount of scrubbing seems to get rid of them. Invariably, the side of the house that’s affected or the car is next to a flower bed that’s been mulched with woodchips. The culprit is the artillery fungus, a group of species in the genus Sphaerobolus. The reproductive structures on these small (1/16th of an inch in diameter) fungi feature tiny cups with a packet of spores in the center. When there’s enough moisture, these spores shoot out as much as twenty feet and stick tenaciously wherever they land, completely harmless but unsightly. Incidentally, the vigorous scrubbing you do trying to remove these spots may do more damage to the paint than the spots themselves – you’re better off just letting them wear off over time.
And then there are stinkhorns – various fungi of the Phallaceae family. Occasionally, you may find an odd egg-shaped structure in your garden. This may not attract much attention until you notice that it keeps growing, and that one day a bizarre creature seems to emerge from it – bright red tentacle-like arms, or a stalk topped by a slimy green cap. Perhaps even worse than their shocking appearance, they emit a fetid odor. This charming group of mushrooms relies on flies to disperse their spores, and so it attracts them by smelling like something horribly rotten that only a fly would be interested in. The mushrooms wither away after a few days, but not before offending the sensibilities if nearly everyone present.
It’s perhaps ironic that the mulch that people use to beautify their gardens may bring things that few people find in the least bit beautiful, but that’s Nature for you. Fungi are the organisms responsible for decomposing wood, and the mulch you laid down is an ideal site for them to settle down. When you get spells of extended rain or humidity that provide the moisture that these organisms need, they make themselves unwelcome guests.
Fortunately, slime molds, stinkhorns, and artillery fungus don’t present a serious threat. They won’t hurt the plants in your garden, and they won’t hurt people as long as you leave them alone. There aren’t any fungicides registered for dealing with them, and there really isn’t any need to treat them anyway. If you’d rather not deal with them at all, consider using other mulch materials – bark mulch tends to not harbor artillery fungus; pea stone doesn’t harbor any of these species. Slime molds will disintegrate with a blast from the garden hose, though that will help to spread them over a wider area. If you’re hosting a garden party that will be attended by individuals with delicate constitutions, you can simply pick up stinkhorns or slime molds and remove them.
