Hardwood Mulch Killing Perennial Plants

Asked April 25, 2015, 8:15 AM EDT

I recently added a top dressing (about 1 inch) of recently purchased hardwood mulch to my perennial garden and it appears to be "burning" the young plants. Some plants die back outright and some have the outside leaves turn almost white in color. I've done this process for many years without experiencing this result: can you tell me what is happening? I fear that the mulch may contain some sort of toxin: can you test for that? I live up the road in Monkton and would be very happy to come to the Hunt Valley office to discuss this matter. Thanks for your help

Baltimore County Maryland dieback sour mulch perennials

1 Response

From your description and photo it looks like you may be dealing with 'sour mulch'. We do not test for this. Mulch that has developed "Wood Alcohol Syndrome" will have a very strong alcohol-like odor as opposed to the pleasant mild smell of properly stored mulch. If you have any doubts about your mulch, aerate the pile and allow it to dry out before using the mulch. See our website for photos and more information. http://extension.umd.edu/hgic/toxic-or-sour-mulchwood-alcohol-annuals-bulbs-groundcovers-perennials-...
Once the mulch is spread the alcohol evaporates fast. Spread or rake the mulch out and make sure there is no smell. The sour mulch usually burns the foliage and does not affect the roots too bad. Cut back any damaged annuals and perennials and remove any dead plants.