Where there's tags, there's no plants.
That happens at our arboretum rock garden, too. Our NARGS Chapter does all the weeding and planting, but no one wants to move or pull tags on the chance that there are not supposed to, or they are just not confident, or they are stepping on someone's toes, as they say. Once in a while, two or three of us better informed members go through and pull and re arrange labels. The fact that many go dormant and retreat underground complicates things, and visitors like to move tags, too. It's been a few years now, and label verification should be on our agenda again soon.