I find white asters tricky to identify. There are a lot of them, and they all just look like white asters. Getting into the weeds with them is a really good puzzle. Part of the identification of Ontario aster can be the relative size of those tiny little lobes of the yellow center flowers. Apparently the pros found them tricky too, because they now have decided they're not Asters. The chromosome crunchers have been at it again. Sometimes I almost wish they could leave well enough alone. Daisies used to be Chrysanthemum leucanthemum. Almost poetic, and kind of fun. White flowered yellow flower? Now they're Leucanthemum vulgare. Ugh! And now what used to be the familiar Asters have become the very unpoetic Symphyotrichum. But of course it is important to get it right. Isn't it?