COLUMBIA, Mo. – Some Missouri trees are producing a gooey, orange slime that seeps and grows.

Bright orange tree slime brings wonder to the woods after cool, wet spring days, says University of Missouri Extension horticulturist Tamra Reall.

This slime from Mother Nature grows from a number of fungi, including budding yeasts that feed on the sugary sap flowing from tree wounds, says Hank Stelzer, MU Extension forester.

One such fungus with the long name Cryptococcus macerans gives no hint of how fun this basidiomycete yeast can be to watch, says Reall. She and Stelzer call it a “slime volcano” because it bubbles and spews goo from common hardwood trees found in Missouri.

The bright orange color results from the production and storage of carotene—the same pigment found in carrots—within the yeast cells.

The slime causes no long-lasting harm to the tree, says Stelzer. Damage is primarily cosmetic and needs no treatment.

Find something interesting on your walk outside? Send questions to @MUExtBugNGarden (Twitter and Instagram). You may ask MU Extension specialists about horticulture topics on Wednesdays, 11 a.m. to noon, at the MU Extension Home Horticulture Town Hall. Register and submit questions at ipm.missouri.edu/TownHalls.