Help! “Dog Vomit Slime Mold” is popping up all over our new garden. - Ask Extension
My husband and I purchased 12 yards of shredded bark mulch from our local landscaping business this spring. Since early July we have had this mold pop...
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Help! “Dog Vomit Slime Mold” is popping up all over our new garden. #941789
Asked August 07, 2026, 9:57 AM EDT
My husband and I purchased 12 yards of shredded bark mulch from our local landscaping business this spring. Since early July we have had this mold popping up and spreading all over our newly landscaped gardens. We still have a lot of the mulch sitting in our driveway but the mold is growing all over that as well. We have used shredded bark mulch from bags before without any mold problems in the past. We are removing the mold daily by spraying it with 50/50 vinegar and water, then removing all the affected mulch but sometimes it is actually climbing up our new shrubs as well and this is becoming a lot of extra garden work to keep up with. The garden is in full sun and we water our new shrubs and flowers at the base of the plant so this mulch isn’t wet unless it rains. Is this a normal issue with shredded bark mulch or should we ask our landscaping supplier to take this back and refund our money? Also what is the best type of mulch for flowers and shrubs in a sunny garden?
Washtenaw County Michigan
Expert Response
Hello
Yes, slime molds are a normal occurrence on shredded bark or wood mulches when they are constantly moist.
You are doing everything correctly. Do check that the mulch does not touch the stems or trunks of the new plants- each plant should be in a “ donut hole” surrounded by mulch. Keep the mulch no thicker than 2-3 inches high around small plants like flowers or hostas, and 3-4 inches high around trees and shrubs.
Slime molds do not harm anything. You can rake them to break them up. In highly visible areas that you water often, you could pull the mulch back, water the plant, then redistribute the dry mulch around the plant. Water the soil, not the mulch where this is practical or is worth the extra effort.
You can also place a soaker hose below the mulch and perhaps use “quick connect” type connectors to set up a watering system so you don’t have to pull back mulch every time you water.
Another method is to water early in the day, letting the surface of the mulch dry out in the sunlight.
Here are bulletins for you about slime molds-
https://www.canr.msu.edu/news/unsightly_slime_mold_sighting_on_landscape_mulch
Scroll down in this bulletin, which has additional ways you can discourage slime molds- https://plant-pest-advisory.rutgers.edu/control-of-nuisance-fungi-in-landscape-mulch/
Yes, slime molds are a normal occurrence on shredded bark or wood mulches when they are constantly moist.
You are doing everything correctly. Do check that the mulch does not touch the stems or trunks of the new plants- each plant should be in a “ donut hole” surrounded by mulch. Keep the mulch no thicker than 2-3 inches high around small plants like flowers or hostas, and 3-4 inches high around trees and shrubs.
Slime molds do not harm anything. You can rake them to break them up. In highly visible areas that you water often, you could pull the mulch back, water the plant, then redistribute the dry mulch around the plant. Water the soil, not the mulch where this is practical or is worth the extra effort.
You can also place a soaker hose below the mulch and perhaps use “quick connect” type connectors to set up a watering system so you don’t have to pull back mulch every time you water.
Another method is to water early in the day, letting the surface of the mulch dry out in the sunlight.
Here are bulletins for you about slime molds-
https://www.canr.msu.edu/news/unsightly_slime_mold_sighting_on_landscape_mulch
Scroll down in this bulletin, which has additional ways you can discourage slime molds- https://plant-pest-advisory.rutgers.edu/control-of-nuisance-fungi-in-landscape-mulch/
