Have you noticed a connection between hot, humid weather and the growth of a bright yellow, rather unsavory looking (unsavory is an understatement) organism on your mulch? You might be dealing with slime mold, a creature with a name as gross as it looks that thrives on wet, hot mulch.
Despite its name, slime mold is not an actual mold (molds are classified as a type of fungus). Rather, it belongs to the Protista family, and, unlike mold, it is capable of independent movement. It ranges in color from bright yellow, to orange, to brown and grey during the latter part of its lifespan. Though slime mold poses no significant threat to you or your garden, it can be a huge eyesore when it comes to family barbecues and outdoor parties, and most homeowners would prefer to see it quickly eliminated. Luckily, slime molds can be controlled, but not through traditional mold-fighting techniques. Chemical killers have no effect on slime mold, and they can be extremely toxic to your yard. The best way to fight slime mold is through preventative techniques that limit the amount of moisture your mulch is getting. It’s impossible to control how much rain your yard will get in a given summer, but, for those of you with irrigation systems, heads and spray times can be adjusted to ensure that mulch doesn’t get soaked through when grass and plant beds are being watered. An irrigation system that lets too much water seep into your mulch is a quick culprit for slime mold growth.
Even during particularly wet summers, you can utilize a number of tactics to keep your mulch from getting too wet. For instance, periodically raking and loosening mulch chips will let air into your mulch and prevent it from becoming water-logged. Raking up accumulated plant debris and overgrowth will also help prevent slime mold growth by limiting areas in which water might pool. Generally, keeping your yard well-aerated and free of excess growth and debris will control slime mold populations. If it does pop up, keep in mind that it is not harmful, and can simply be dug up and disposed of with a shovel if it becomes an issue. When handling slime mold, be sure not to get it too close to your clothing or skin, because it can leave a staining residue the approximate color of dog vomit, and nobody wants that.