I have two Purple Dome asters. One stays short and the other gets very tall. Perhaps one was mislabeled or some nursery grown plants were not stable and reverted to a taller parent. If you want a shorter aster try a different Purple Dome plant.

I have one that I received at a MN GW plant swap about 6 or so years ago. It was passed up by everyone there, so I rescued it. It was labeld Purple Dome Aster and I beleive it is such. Since it had been passed up by everyone I was leary of it (hadn't looked up anything on it) so I planted in the gardens at the lake. BIG mistake since it has grown into a 2ft bush that blooms beautifully and I only get to enjoy it on the weekends. If I would have known it was going to be such a nice plant I would have planted at home to enjoy nightly in the fall. It's vey well behaved, has not seeded all over the place like other Asters.....

Sandy

My Purple Dome gets about 13-14 inches and is covered wi th blooms every fall. My problem is that the deer love it and just eat all the blooms off, So I start spraying it as soon as buds appear. Mine are just in good garden soil,