Q&A: Acidic mulch

A: Actually, oak leaves and pine needles are two of my favorites for mulching. Although they can lower the pH of the soil, the degree to which they do is negligible. But if you're concerned about the effect either material might have on your soil's pH, you can use them to mulch plants that prefer acidic soil. Or you can compost them first, because the pH of finished compost is usually neutral, regardless of what you put in the pile.