Slime Molds

Slime molds are the red-headed stepchildren of the garden world. Not a plant, not an animal, recent research has created more questions than answers about this garden visitor.


This species will appear in your garden. It won't hurt your crops, in fact, it makes nutrients more readily available. This is one of those topics that just caught my attention and I decided to share what I found. Enjoy!


Slime molds often appear after it rains. They can be yellow, red, orange, blue, gray, black, clear, beige, or even hot pink. They can be flat, lumpy, or a fat, rounded glob. Some slime molds look like thousands of tiny balls, while others look like thready networks. One group is called dog vomit slime mold! Slime molds usually grow on rotting wood and mulch, but they can also occur on tree and shrub leaves, berries, succulents, and other plants. The presence of slime mold does not hurt living plant tissue, since it doesn’t usually last for very long. At one stage, they look like somebody spilled something foamy on the ground (the infamous dog vomit slime mold). Slightly disturbing, these shiny, lumpy spills move on their own volition, yet they have no brains. At another stage, tiny, individual critters look more like flowering moss, with a small sphere waving around at the end of a stalk. Slime molds (myxomycetes) are affectionately referred to as "myxos" by scientists and other fans.


Slime mold taxonomy​

Slime molds are members of the Protista kingdom. Believed to be over a billion years old, slime molds are considered to be life’s first attempt at joining individual cells into complex organisms. There are actually two types of slime mold: acellular and cellular. Acellular slime molds have many nuclei (the part of a cell that holds DNA), but only one cell wall, during the plasmodium stage. There are 1,000 known species of acellular slime molds. There are only 70 species of cellular slime molds, which are made up of individual cells.


Slime mold lifecycle

All slime molds start out as spores, but the way they get there is amazing. Cellular slime molds, as individual cells, emit a chemical that calls other cells to huddle up into a slug-like structure that eventually becomes a stalk, rather than a blob. These mindless stalks are able to spew ammonia to keep competitors away, as they generate spores. Spores are then released from these parenting bodies, usually into the wind or on a water spray (like fungi). The spores then germinate (like seeds) and then join with other germinated spores to form zygotes (like mammals). These single-celled zygotes feed on decaying wood, fungi, bacteria, and plant material, growing into a mass called a plasmodium. These plasmodium can reach several feet in diameter, with no neurons and no central nervous system, but a surprising ability to solve problems. [The largest recorded slime mold was nearly 60 square feet in size!]

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Crazy experiments with slime molds

We humans think that we’re pretty smart. We attribute some level of intelligence to our pets and other favored species. As life forms become more foreign, we are less likely to consider intellect or self-awareness, but this might have to change, in light of recent experiments:
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• If you chop up a slime mold and spread its pieces out in a maze, the pieces will pull themselves back together and continue their search for food.
• Also in a maze, slime molds will withdraw from dead-end spaces that have no food
• Slime molds leave behind a mucus trail as a ‘spatial memory’ to remind themselves of where they have already been (and exhausted food sources)
• They will choose the healthiest foods when offered a selection. (How do they choose without a brain?)
• When provided with food located in the same places as primary resources in major cities, slime molds have recreated the railway and highway systems of those cities! (Engineers are now considering using this ability of slime molds to help design cities around geographic formations and other limiting factors.)
• Experiments involving changing conditions from favorable to unfavorable on a timed schedule have demonstrated that slime molds also have some sort of an internal clock.

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Slime molds will not hurt your garden, unless they are very thick and very persistent. In fact, they help break down dead complex structures into nutrients that your plants can use. Usually, they are only visible for a short time. If you absolutely cannot stand the sight of slime molds, you can use a powerful spray of water to break them up (and spread spores in all directions), dig them up with a pitchfork or shovel and add them to the compost pile, or apply fixed copper to the area. Keep in mind that slime molds will reappear in areas with plenty of shade, moisture, and organic material, no matter how many times you try to get rid of it.