They’re not exactly beautiful. At first glance, you might guess that your neighbor’s dog has vomited on your lawn, but don’t go knocking on their door quite yet. These flattened slimy or spongy masses are actually living organisms known as slime molds.
Growing up to two feet in diameter, slime molds may be white to yellow, pink or tan. Although they look slimy, they are actually fairly resilient when prodded. Unlike plants, slime molds can travel several feet a day. And despite their name, they are not at all related to molds or other fungi. Rather, they’re considered members of the Protista. If you want more detail than that, let’s just say it’s complicated.
Slime molds feed on microscopic organisms that live in rotting plant matter. They are found on lawns, wood bark mulches (or stumps, as shown here), and even on the decaying leaves in your gutters. Damp weather encourages their spores to germinate and grow. When conditions dry out, puffball-like structures produce a new generation of spores. The slime mold will then break down, leaving its spores behind as a brown powdery legacy.
Although they don’t feed on your plants, any slime mold covering and shading a plant should be removed. No pesticides are labeled for use on slime molds. Instead, you can rake them up, bag them for disposal, or disperse them with a strong jet from the hose.
You can also do nothing. They will eventually disappear on their own.