This unusual “fungus” is just one out of over 900 different types of slime mold. Slime mold is the casual name given for a soil-dwelling, single-celled primitive organism that combines with other cells to form a plasmodium—essentially, a blob (kind of like an amoeba).
Slime mold is completely harmless to humans, animals, and plants. Perhaps the only (rare) risk to neighboring plants (particularly small seedlings) is being smothered by the blob as it grows.
But slime mold isn’t after your plants, even if it’s growing around the base of the stems—it feeds on decaying organic matter, which is why it’s often seen in mulched areas where the mulch is starting to break down.
Dog vomit fungi appear on every continent; their origins are in the trees that make up the mulch they usually grow on. They can be found in bark mulch, rotting logs, tree stumps, untreated lumber, and leaf litter.
Like true fungi, slime mold is spread by spores through the air. After it goes through the slimy stage, it begins to crust over and turn brown. If disturbed, the spores will puff up (like a brownish-black cloud of dust) and distribute to nearby areas.