Answer: Early spring is really the best time to transplant and divide asters, but you can still transplant it now. Be sure it is well watered the day before, try to take the entire root ball, and then water it in well afterwards. Be sure it receives adequate nutrients and moisture while it reestablishes, too.
In my experience, asters do best if divided about every other year. If the plant is three years old, it is probably in need of division. You might want to consider doing that early next spring because it will rejuvenate the plant, help with size control and also give you more of them to add to the garden!
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