Star Cluster has now been here 3 summers and 2 horrible winters: one sopping wet winter and one polar vortex. It has been disease free and flowers well. However, it's very large. Grows about 24" tall, then flops over and grows up again. If I let it keep going, it would most likely cover a good 4' space. Good coreopsis if you can find the right spot in your garden.
Hi Patty
From the picture you posted your star cluster looks solid white? Does it have a dark spot on the petals near the center?
I purchased one this spring and it has some dark on the petal.