Slime Mold Solutions for Your Garden

The colorful fungus known as slime mold isn’t a threat to your garden, but it still may provoke some questions. Howard Garrett profiles slime mold and provides some tips on how to deal with it.

  • slime-mold
    Though it may be a surprising sight in your garden, slime mold doesn't pose as a threat to your plants, especially the larger ones.
    Photo by Howard Garrett

  • slime-mold

Question: I’ve noticed a strange fungus growing on my mulch. Do I need to worry about it affecting my garden or ornamental plants? 

Answer: You may have seen this strange, vomit-looking mass in landscape beds, in the vegetable garden, or even around trees. It could be white, yellow, tan, bright-red, or most any color — even multi-colored. This visitor is a fungus commonly called slime mold, and thankfully it’s not a problem, especially for larger plants.

Slime mold grows and feeds on dead and decaying organic matter. It generally doesn’t hurt anything, isn’t dangerous to pets, and usually needs no treatment. The only scenario I’ve ever seen in which this fungus hurt plants is when it grows over small plants and smothers them. When simply growing on the mulch (the most common place to see it), there’s no danger of plant injury. Its name — slime mold — sounds scary, but it’s just a saprophytic fungus helping break down organic matter, especially in moist environments. It can even be seen growing on hard surfaces that stay moist. Some of the slime molds in turfgrasses look like cigarette ash and will leave black stains on your shoes. This form of the fungus can also be yellow or other colors.

If you want this interesting-looking visitor gone, any of the organic fungicides will kill it. Slime mold, as well as any mushrooms or toadstools, can be knocked out with baking soda, potassium bicarbonate, cornmeal, cornmeal tea, hydrogen peroxide, or commercial products like BioSafe Disease Control. Physical disturbances, such as mowing the grass or scratching the slime mold in beds, are also effective.

All these growths are mostly prevalent when there’s excess water and organic matter — so, watch how much you water your garden. 

--Howard Garrett, host of The Dirt Doctor and author of more than a dozen books, including The Organic Manual

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