The answer to 'why is my mulch invasive plants' is that certain types of mulch can contain weed seeds or plant fragments that can sprout and spread, becoming invasive. This is common with wood chip or bark mulches that are not properly composted or heat-treated before application. The mulch can also act as a growing medium for existing weed seeds in your soil.
To prevent this, it's important to use a high-quality, weed-free mulch from a reputable supplier. Opt for finely shredded or composted mulch that has been processed to kill any weed seeds or plant material. Apply a 2-4 inch layer of mulch around your plants, being careful not to let it touch the stems or trunks. This will help block light and suppress weed growth while also retaining moisture in the soil.