toxic mulch

Asked June 1, 2017, 11:17 AM EDT

Hi. I just recently put down 3 yds of mulch. Two days later I noticed that the leaves of my various plants (e.g., hydrangea, flower plants, hosta, asitble, other) that were touched by the mulch when I spread it, have withered and browned or died back completely.
Is that normal or could there be something in the mulch toxic to the plants? I am concerned that eventually the rain will cause the whatever is in the mulch to reach the roots of the plants. Thanks for taking my question. Rodger

Stark County Ohio

1 Response

Hardwood mulch can go bad when improperly stored and the reaction in the pile goes from aerobic to anaerobic. The mulch develops a vinegar or sour smell. This type of problem does not occur if the pile of mulch is properly stored. If purchased and you notice the odor do not spread the mulch but spread it out away from the plants and allow air and water to penetrate the mulch and change the reaction back to aerobic. Then the mulch will be fine again to spread on the beds. If already spread and the plants are suffering, you can remove the mulch but some plants may die from the gases that have been already produced by the mulch. This article from Michigan State extension provides more info.