Purple Dome Aster

I am a bit cautious about asters .. I have ripped out quite a few in the back garden but allow some sneaky ones their space as long as they behave. Powdery Mildew is what really makes me crazy .. thus the ripping out of etc ... This is Purple Dome aster which is supposed to be rather resistant to that unspeakable scourge I battle .. not too bad looking an aster .. and not too leggy at the moment .. still on probation though !