I have Brass Buttons planted in my garden in Puyallup, WA and it is spreading like wildfire! It is growing right up to and around all the perennials in the garden and I am wondering if this will be a problem or if I should just leave it be.
You could always send it to me! :) I'm looking for something like this to put into my flagstone patio I'm making, to fill in between the rocks.
Personally, I've never dealt with this plant, but I would think that with plants like daylilies, iris and hosta, or others with a thicker base, it should be no problem. But you might want to watch any that have less substance to their roots and stems, in case it strangles those.
It is so low growing, it will not be a problem crowding out any larger growing perennials. And like most creeping, mat-like groundcovers, it is pretty easy to remove where not wanted.
I doubt one would have great success with this plant in zone 3/4. While it is alpine in origin so supposedly tolerant of cold, hardiness in zone 4 is dubious and it certainly wouldn't be evergreen. Most sources list it to zone 5, others zone 7.