The answer to 'why is my mulch dead trees' is that old, decomposed mulch can actually be harmful to plants and trees. As mulch breaks down over time, it can become dense and matted, preventing water and air from reaching the roots. Additionally, the decomposition process can release compounds that are toxic to plants.
Some common signs of dead or dying mulch include a foul odor, a slimy or compacted texture, and a lack of new growth or discoloration in the plants or trees it surrounds. To fix this issue, you'll need to remove the old mulch and replace it with a fresh layer of high-quality mulch, such as wood chips or shredded bark. Be sure to spread the new mulch in a 2-4 inch layer, leaving a few inches of space around the base of the plants or trees.