I can't remember where I read this, but within the last year I know I've read that research was published indicating that soil acidification via conifer needles does not occur on anything but a temporary basis. Over time (a few years or so) whatever acidification initially occurs reverts back to the natural pH of the soil.

Pine straw is used a lot here too (Georgia) and I doubt it makes much difference in the PH.

The things I don't like about pine straw is that it breaks down easily, tracks into the house (on your feet if you are in the beds a lot) and really needs to be refreshed every year or even twice a year. I prefer pine bark nuggets. I only use pine straw on hillsides because it doesn't slide down the hill.

Are you going to use your own pine straw or buy bales? I would leave the old pine needles and just put more on top. As I said, they break down easily and make good organic material in the soil.

If they are present on your property, you should use them.

I get some from two white pines on our property and like it a lot - wish I had more.

We use pine straw (same as needles)in our Memorial Garden down town. We replace it every year. We do not rake it off, but rather add the new on top of the old. It breaks down and into the soil making the soil more friable.

For me, pine straw is pretty close to being the ideal mulch. It's easy to move around when I want to scatch materials into the soil (like Mills Mix or RoseTone). I've found that my roses have far fewer problems with diseases when I remove old mulch every year. Pine straw makes that task much easier. Also, if applied at a reasonable thickness, it controls weed growth as well as other, more expensive, types of mulch.

Thank you so much for all the responses. Yes, abundant amounts of pine needles are present on my property, and every fall the rose beds naturally end up being covered by the winter with pine straw anyway.

That makes me feel better!