Answer: Mulch can help suppress weeds, moderate soil temperatures and help slow water evaporation. In the case of organic mulch materials (compost, shredded leaves, bark chips, etc.), as the matter decomposes it will leach nutrients into the soil. It's a win-win situation. In the case of non-organic mulches, they won't break down, but they will still suppress weeds, etc. When mulching around trees and shrubs, keep the material a few inches away from the trunk or main stems of the plants. If the mulch, whether organic or not, is piled up against the base of the plant (like a volcano), it will hold too much moisture against the bark and can cause rot. A mulch 3-4" thick works best to suppress weeds. Yes, you can apply too much of a good thing. A very thick mulch tends to shed water so getting water to the roots of your plants can be difficult. If you think the mulch is too thick, rake it away and then replace some of it. 3-4" of mulch is just about right.
Best wishes with your landscape!
Q&A Library Searching Tips