Do pine needles make the soil acidic for mulch?
If pine needles makes an acid soil, are there certain plants that do not like having them used as mulch around them? We had grape vines die because they were close to pine trees. Now at our home here we have a peach and plum tree close by. Use them for mulch or not?
Also, Would it help our pine tree to keep a layer of needles under it out to it's drip line to keep moisture in, or does it not help or harm the tree.
You can use pine needles as mulch around anything you would like. It takes years for the pH in the needles to change the soil and by then, the tannins are gone.
You would have to use very large quantities of pine needles to effect the soil pH. It will help your pine tree hold its water very well.