I live in zone 5b- in West-Central Illinois, and wonder what's wrong with the Aster's in my full-sun garden. My soil is very rich and black, and I have the garden paths mulched with wood chips. I've had the asters for 2 years, and both years they have turned brown/black. From the ground up nearly 3/4ths of their stalks- they look like they are dying. Very few blossoms.
I have a Michaelmas Daisy (Aster novi-belgil) and a New England Aster (Purple Dome). We had a WET June followed by extremely dry and HOT July here in West-Central Illinois. Maybe these plants are not suited for my garden. Any help will be greatly appreciated.