Blueberries do best with a 2-4" mulch over the roots to conserve moisture, prevent weeds and add organic matter. Pack the soil firmly around the roots, then mulch the planting with 2 to 4 inches of sawdust, peat moss, oak leaf or pine needle mulch. The best way is to incorporate sphagnum peat all around the blueberry plant’s base about once every year. all work well. These types of mulch are acidic and will help maintain a low soil pH. We use clean wood chips, but bark mulch, acid compost, pine needles or grass clippings all work well. Blueberries have dense, shallow roots and do best with 2-4 inches of mulch over the roots to conserve moisture, prevent weeds and build organic matter. Replenish mulch as needed. Mulch also helps maintain soil moisture, prevents weeds, and reduces soil temperature in the summer. Bark mulch, acid compost, sawdust, grass clippings, etc. Mulch for Blueberries. In order to become successful in growing, you will require to pick the best mulch for Blueberries.. Mulch will aid to prevent weeds, correct the soil temperature, and keep a … For effortless growth Blueberries require acidic, well-drained soil and 4-6 inches mulch over the roots. Another method way on how to acidify soil for blueberries is to ensure that you fertilize the blueberries with some acidic fertilizers. Repeat every other year. Mulch well.