Plants often develop a very shallow root system that is more subject to damage during severe drought or cold weather. Excessive application of mulch can result in a situation in which roots are growing in the mulch and not in the soil. Over-mulched plants are easily damaged when herbicides and fertilizers are applied and during periods of drought stress. Mulching an area that is poorly drained can aggravate the condition. Their role is to break down the organic matter, which releases nutrients.
Slugs are the most likely harmful pest.
An application of wood ashes or diatomaceous earth at the base of the plant should provide some slug control. An alternative is to use slug baits or pellets. In some cases, mice and voles may tunnel under mulch and cause damage by chewing the plant bark. Pull the mulch back 6 inches from the stems. Published by the North Carolina Cooperative Extension Service Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914.