Yes, you can use untreated wood chips mulch. First, pile them together so that they can start to break down and decompose. Then transfer them to your plants, providing rich mulch for your plants. Untreated wood chips are safe for your soil as they have no traces of herbicides or pesticides.

Untreated wood chip mulch is better for the environment, but won’t do a great job of suppressing weeds. It also has the potential to attract termites, especially if you live in an area where they’re common. Treated mulch either comes from recycled wood that was pressure-treated in a previous life or has been pre-soaked in herbicides.