being taken over by some form of wild, fruitless strawberry.

Fruitless or small fruits? Yellow or white flowers? (Not that it
really matters, I'm just curious whether it is the same one we have).

I have another place under some white pines where low-growth
blueberries are growing wild. I've seen wintergreen growing with low
growth blueberries in the wild, so I'd like to transplant my
wintergreen to this more hospitable area.

Yes, give this a try. They both like acid soil. The pine needles
probably make a better mulch than anything you would add (you *are*
leaving the pine needles there, I hope). If you want to add compost
or mulch, make sure it is acidic - such as pine bark or coffee grounds
- but if there seems to be a reasonably rich layer of organic matter I
might leave well enough alone.

I'm jealous. We've tried to grow wintergreen, but we're much more in
the situation of trying to manufacture a suitable place for them,
rather than having pine trees or anything similar. I think we've
killed 2 nursery plants so far, with one hanging on for dear life (and
probably doomed unless we can get the soil pH down and who knows what
else). At some point we may give up and pick plants to match our
soil, rather than trying to amend soil to match the plants.