Gardening tips: slime mold!

How to deal with an unsightly garden visitor

Editor’s Note: The University of New Hampshire Cooperative Extension provides weekly gardening columns in which Jeremy DeLisle answers questions from local gardeners. 

Q: After the recent rain showers, which I am so happy to receive, there is a strange pinkish-orange slime in my garden which looks unsettlingly like my dog couldn’t keep his meal down. It’s pretty gross-looking stuff. Any idea what it could be? Should I be concerned about an alien invasion?

A: It sounds as though you have an interesting garden visitor know by the not-so-flattering name of slime mold. These are fungus-like organisms often recognized by the aggregation of tiny amoeba-like organisms that swim or drift together in films of water on the surface of decomposing organic matter. As they merge, they consume bacteria crossing their path.

Once several of these cells merge, they form an aggregation in which the cells fuse together to form what is known as a plasmodium. This is what we see and recognize in our gardens. It may range in color from white or yellow to pink, orange, or brown. Although brainless, this plasmodium is able to move in search of food and can determine when resources are scarce enough to warrant reproduction for survival. Eventually, spores are produced that will drift away on wind or be carried on by animals to settle in new locations where the process will begin all over again.

Where to find them
Preferred habitat for slime molds include garden mulches, damp forest floors, rotting logs, and anywhere with ample amounts of moist organic matter. Moisture is key to survival for this organism, which will continue to grow and move while suitable conditions exist.

Yes, slime molds can move, although slowly in relation to the pace we are accustomed to, and may grow up to a foot or two in diameter. Some species grow much larger, but those we regularly see in the garden here in New Hampshire generally don’t exceed this size. This is to say, gardeners needn’t worry that they will grow to envelop their gardens. Whew!

What’s a gardener to do?
Control in the home garden is for aesthetic purposes only, as the slime mold will not cause harm to your healthy garden plants. It will, however, aid in the decomposition of decaying organic matter, thus fulfilling its role in the nutrient cycling process. Once moist environmental conditions recede, slime molds will release their spores and the aggregation will die.

Gardeners looking to quickly remove these interesting growths from their gardens need only rake or cultivate them into existing mulch or turf to break them up, or collect them along with a small portion of surrounding organic matter and remove it from the garden.

In-the-know gardeners should know that these little marvels of nature will likely return at some point when conditions are favorable; however, we can all rest assured that we are not witnessing an alien invasion or reoccurring case of canine indigestion. Rather, our gardens are functioning as they should, serving as a healthy environment for fascinating organisms such as slime mold to complete their life cycles. From this gardener’s perspective, a garden good enough for slime mold is good enough for me.

Jeremy DeLisle is the program coordinator for the UNH Cooperative Extension Education Center. The center answers questions about gardening and more at [email protected], or by calling 877-398-4769 Monday through Friday, between 9 a.m. and 2 p.m.