If you have pine wood chips and needles available for use as a ground cover or mulch, you probably don't want to use it right after it is chipped. The chips and needles have a high acid content that may affect your plants. But if you let the material sit, after 9 - 12 months, the acidity will be reduced (and it'll be a richer mulch) and it will be safe to use. If in doubt, you can get a soil pH tester and test the material.