Melissa Caggiano, from the Executive Board of the NYS Nursery and Landscape Association asked for information on the horticultural science behind the use of mulch in garden beds. I put together this statement, which I hope helps.
*** If you need a more formal version of this on letterhead, please contact me at firstname.lastname@example.org.
Mulches are frequently used in landscape beds to reduce weed pressure. Cregg and Schutzki (2009) found that mean weed counts for dandelion, annual grasses, and redroot pigweed were significantly lower in plots mulched with organic (bark or wood based) mulches than in plots with no mulch and that the weed control was as good as that with hand weeding plus chemical control. Amoroso et al. (2010) found similar results with different types of mulches. Weed control , as grams of weeds per pot, in mulched treatments was equal to or better than chemical weed control. In a review article, Chalker-Scott (2007), documents reduced water loss from soil, reduction in compaction and loss of soil to erosion, and moderation of changes in soil temperature with the use of mulch, all of which maintain plant health and survival.
Amoroso, G., P Frangi, R. Piatte, A. Fini, and F. Ferrini, 2010, Effect of mulching on plant
and weed growth, substrate water content, and temperature in container-grown
giant Arborvitae, HortTechnology 20 (6):957-962.https://doi.org/10.21273/HORTSCI.20.6.957
Chalker-Scott, L. 2007, Impact of mulches on landscape plants and the environment – A
review, J. Environ. Hort. 25(4):239-249.
Cregg, B.M. and R. Schutzki, 2009. Weed control and organic mulches affect physiology
and growth of landscape shrubs, HortScience 44(5):1419-1424