I have a Japanese Rose and I was wondering if it is invasive and how should I look after it? Also will deer eat phlox? Thanks Marie
Kerria japonica spreads by underground suckers. Many plants do so. I don't think it will take over your garden though, just sever the sucker from the parent and pull it up whenever you see it.
Specimen is too constricted in its present condition, it suckering and becoming broader would make it more relaxed and attractive looking.