What was the white area that developed on mulch after a heavy rain?


After a severe rain storm the other day, this white area developed under a grouping of trees, on some mulch. The next day it began turning black. What would be happening and are the plants near by or the trees in jeopardy of getting some form of fungus or disease?


Jonathan Foster, Home Horticulture Outreach Professional

I believe what you are looking at are slime molds, a somewhat distasteful name for a fascinating life form! It looks most like the truly awfully named dog vomit slime mold. While they can be quite scary to see appear in the yard, they are actually beneficial protists (a separate taxonomic kingdom from both fungus and plants) that feed on decomposing organic material. They don’t pose any risk to your trees and will typically disappear when things get hotter and drier.

Happy gardening.