Sour Mulch

 

by Karen Weiland, Advanced Master Gardener

 

 

 

Wood chips and bark nuggets have been used by gardeners for years as mulch around landscape plants.  Mulch is very beneficial to plants in that it prevents weed growth, evaporation of moisture in the soil, keeps the roots cool during the hot summer months and enhances the look of a landscape.  Mulch can however turn sour if it is stockpiled too high (taller than 5 to 6 feet) for a long period of time. This mulch is known as sour mulch or mulch with wood alcohol syndrome.

Mulch becomes sour when lack of oxygen and high moisture towards the center and bottom of the pile starts a process known as anaerobic fermentation.  This process produces by-products such as ammonia, alcohol and organic acids that can harm plants.  Large piles, such as those accumulated at lumber mills or companies that manufacture mulch can develop huge piles that can lead to sour mulch.  Pine bark is not as prone to forming toxic by-products as hardwood bark is.

Once sour mulch is spread, plants usually show symptoms within a day with some recovering and some not.  Many plants can be affected, from herbaceous perennials and annuals to newly planted trees and shrubs.  Plants may show some wilting and the some of the foliage may turn white or light tan as if bleach had been thrown on it. The turf next to sour mulch may turn a light yellow color.  Do not apply fertilizer to plants that have been injured by sour mulch.  If plants recover, but show some lack of vigor, a side dressing of nitrogen can be applied mid summer.  Avoid fertilizing during hot, dry weather.

Sour mulch will have a vinegery, rotten eggs or ammonia like smell which will go away quickly once it is spread out.  It can also feel hot.  If stockpiles of mulch are suspected of being sour, the pH should be checked.  Sour mulch pH will be very low, ranging from 2 to 3.5.  Properly composted organic material will have a pH of 6.0 to 7.2.   If it is found to be sour, the pile should be turned to provide aeration, have lots of water applied to it to leach out the toxins and have an ample amount of lime applied to it to bring up the pH.  The mulch should be safe to use after a few weeks.

In a nutshell, never use mulch around your plants that is hot or smells nasty!

 

As always, Happy Gardening!

 

More information about gardening and related subjects can be found online at www.hort.purdue.edu/ext/garden_pubs   The Purdue University Cooperative Extension Service can be reached at 499-6334 in LaGrange Co., 636-2111 in noble Co., 925-2562 in DeKalb Co. and 668-1000 in Steuben Co.

African Violet Care

by Karen Weiland, Advanced Master Gardener       African violets are one of my favorite houseplants.  Their care takes little effort, they do not take up a lot of space and they bless me during the winter with beautiful blooms. A pleasing temperature for these houseplants is 65 to 80 degrees.  Anything above or …

Read More >

Road Trip Season

Summer is almost over… that’s right, I said it. I’m not happy about it either. But the keyword here is “almost.” That means you still have time to get those last minute summer plans in that you didn’t have time to do before. I know somewhere on that list of things you want to do …

Read More >

Peanut Butter

I’ve lived here most of my adult life and there is one thing I never get tired of… the Amish Peanut Butter!  It’s crazy to think that this little condiment can literally be used for breakfast, lunch, and dinner!  If you are unfamiliar with this gooey smooth rich peanut butter, let me give you a …

Read More >

Get your official copy of our

Destination Guide

Request Printed Guide

View E-Guide

Stay informed and sign up for the

Shipshe E-Newsletter

  • This field is for validation purposes and should be left unchanged.