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What is Orange Mold?

Laura M. Sands
Laura M. Sands

Orange mold is a particular type of slime mold often found outdoors. It is considered harmless, as it does not damage plants or hurt people. While it is primarily orange in color, this unique type of mold can sometimes also appear to be red or pink at times. When it first materializes, it is moist and fluffy in appearance, but as it ages, the mold dries and becomes crusty.

As it thrives on decaying organic matter, orange mold survives off of bacteria and fungi, as well as tiny organisms that may not be visible to the naked eye, but are nonetheless present in gardens and wooded and moist grassy areas. It also relies on moisture to survive and is common in areas of high humidity. Humid regions that sometimes endure very cold seasons, however, will notice a decrease in mold as temperatures decline. Since it is considered harmless, many who are familiar with the fungus do not attempt to remove it unless it grows to large proportions or becomes too unsightly.

Orange mold is commonly seen in gardens that utilize mulch for moisturizing needs.
Orange mold is commonly seen in gardens that utilize mulch for moisturizing needs.

Black spores live inside of orange mold and may be spread if it is opened. When removing it, experts recommend doing so in such a way as to prevent spores from becoming airborne. Shoveling it away is the method some gardeners use when it is determined that removal can be done without cracking or breaking the mold.

Orange mold quite commonly occurs in gardens that use mulch to help retain moisture needed for good plant nutrition. In these types of environments, however, slime mold is more likely to grow on top of the mulch. Sometimes referred to as dog vomit, due to its coloring and flat, lumpy appearance, orange mold is far more unsightly than it is hazardous.

Slime mold can also take the appearance of yellow or red mold. Often, these growths are vividly depicted in photographs of wooded forests, as they are commonly also found on decaying leaves and rotting logs. Slime mold can also be found atop moist animal feces.

Orange mold is not an actual fungus, but is a Protista. The difference lies in the fact that slime molds are single-celled organisms, while all other fungi are multi-celled organisms. Slime molds grow and move by creeping and, at one point in history, were actually considered a unique animal species.

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Discussion Comments


Can orange mold kill fish? I have a fish tank lid I built from scratch out of wood, and orange mold is starting to grow on top of the lid.


In one room of our Florida home (window faces north) we have a bedroom that had not been slept in over a year (dusted and vacuumed regularly.)

Upon closer inspection, we found comforters stored in the closet dotted with orange "polka dots." Upon a closer look, I found the "dots" on the lamp shades and along the baseboards where the two twin beds hug the walls.

I cleaned the fabric items with bleach, water and sunlight, cleaned the woodwork with Soft

scrub with bleach and a scrub pad. I've never had this problem before. What is it, and will it return while the house is closed for the summer/fall? We are snowbirds and have been here seven years and have never experienced this before and it was only in one room!

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    • Orange mold is commonly seen in gardens that utilize mulch for moisturizing needs.
      By: Wendy Kaveney
      Orange mold is commonly seen in gardens that utilize mulch for moisturizing needs.