Keeping good records - A is for Aster

Late summer flowering in Mrs. Phactor's perennial garden runs largely to the color pink but in a wide variety of plants. Here and there a little white and pale blue sneaks in.  In the ongoing quest for more diversity, an aster was purchased at a native plant sale and then another aster purchased at a perennial sale elsewhere and both were planted to help fill in an area largely denuded by herbivores of one sort or another.  And now several months later both asters are flowering, and both have pale blue-lavender ray flowers and yellow disk flowers (Does anyone need a refresher lesson on the inflorescences of composites?  Remember, those ray flowers are not petals.). Exactly what is what is a fairly reasonable request, and one species was written down in a notebook, maybe, if that's what it refers to, and the other one was not, but which is the "other" one? Well, you don't teach plant ID for over 40 years and not be able to deal with this. Ah, yes, a quick garden check on the plants in question, asters indeed, and to make matters short, sweet, and easy, name tags had been placed appropriately at their bases when these were planted. Yea! The larger species was Aster laevis, the smooth blue aster, the Illinois native, standing about 4' tall with flowering heads (remember they aren't flowers) little over 1" in diameter (top - 2 heads). The smaller species was Aster azureus, the sky blue aster, standing about 2.5' tall with flowering heads about a half inch in diameter. Not sure if smooth refers to blue or something else, and both look pretty lavender.  Both are quite delicately handsome, but TPP predicts having trouble remembering which is which in the future, which is why they were planted almost next to each other to aid the memory. To aid our recall, some notes were added to the master list of garden plants.