Plants don’t really change their names by themselves. Botanists change the names of plants, and when they do, life can get confusing, even frustrating, for anyone interested in gardening. Let me start at the beginning. My plan for this week’s column was a straightforward report on those favorite fall perennials, asters and chrysanthemums.

The first article I read about asters said that the genus Aster once contained about 6oo species in Eurasia and North America, but new scientific information in the 1990s resulted in that number being dropped to about 170 species in Eurasia and only one species in North America. Are you following me? Basically, it means that those lovely, purple and white, daisy-like flowers that our grandmothers called asters are no longer members of the genus Aster. They are now members of the genus Symphyotrichum.

I suppose I should back up even more to try to clarify what I am saying. Every plant is a member of the Plant Kingdom. Other categories, in descen...