05/30/2026
There are different kinds of mulches:
--Living: ground covers, cover crops
--Synthetic: such as recycled pieces of rubber, landscape fabric, sheets of black plastic
--Inorganic: stone, concrete, bricks
--Organic: cardboard, newspaper, compost, sawdust, nutshells, wood chips
According to a published* review of research articles on the topic, the overwhelming choice for most beneficial landscape mulch is arborist wood chip mulch. This kind of mulch provides many more benefits than drawbacks than the other choices. The benefit of any kind of mulch is to: reduce the loss of moisture from the soil, reduce soil erosion, moderate soil temperature and reduce w**ds. Some kinds, though, can actually damage soil and plants or do as much harm as good. Living mulches can compete with the desired plants for water, nutrients and space. Synthetic mulches can contaminate the soil as they decompose or reduce the movement of water and air between the soil and the atmosphere; landscape fabric reduces the movement of gasses by a factor of 100 compared to 4” of arborist wood mulch! This movement is necessary for plant and soil health. While inorganic mulches don’t have to be replaced frequently, they can also be less effective as methods of reducing w**ds. W**d seeds and soil can blow in on top of stones, leading to the growth of w**ds that are difficult to control.
Wood chip mulch can be applied in a deep enough layer (4”) to restrict w**d growth without reducing the exchange of air and water. Wood mulches also support beneficial microbes that support soil and plant health. Arborist wood chip mulches—as the name says—are available from tree services that run clippings, limbs and trunks through the chipper. Some homeowners and landscape professionals have been reluctant to use these because of some misconceptions about wood mulch: 1. According to this article, wood chip mulch which is acidic will not change the pH of the soil—the sheer volume of the soil in a yard or landscape offsets any possible change. 2. Coarsely chopped wood chips won’t injure plants or spread disease even if they come from diseased trees. 3.Some finely textured, shredded wood mulch can form an impermeable mat, restricting air and water flow. A homeowner can offset this by breaking up the mat during a season with a heavy rake or other implement. 4. One myth is that woody mulches attract pests, but the decomposition process increases microbial growth that overcomes harmful pathogens. W**d seeds are inhibited from growing due to the lack of light in lower layers of deep mulch.
A study reported in the American Society for Horticultural Science journal (https://journals.ashs.org/view/journals/hortsci/44/5/article-p1419.xml) confirms the benefits of mulching, noting that it increases soil moisture retention by reducing evaporation and competition from w**ds for that moisture. A nine-year study compared the growth and health of shrubs in similar plots that were mulched with various materials or not mulched. At the end of the nine years, the mulched shrubs “continued to have a significant growth advantage over unmulched plants.” In addition, there was no significant nutrient “tie-up” effect, that is, the myth that wood mulch reduces the amount of nitrogen in the soil that is available to plants. There actually were higher nitrogen levels in the leaves in the mulched plots. This expected disadvantage is one reason people cite for avoiding the use of wood mulches.
While putting wood chips on garden beds is a hard job, it has a great reward in healthier plants and soil. For more information on mulch options, see ’s fact sheet on mulch at https://extension.illinois.edu/sites/default/files/how_to_select_mulch.pdf.
*In the Journal of the National Association of County Agricultural Agents, December 2022.(https://www.nacaa.com/journal/c6b61258-c158-478e-b92d-a6aaa73a71b8).
