Sow the seeds indoors in pots or containers, about 15-20 days before the last frost. The seeds are big enough to be sown directly in the intended location, which can be done after the soil begins to warm in the spring. Sow them in light soil, cover them lightly and water just enough to moisten the soil.
Caring for Aster Flowers
Once transplanted, give them time to establish themselves by regularly watering them. Caring for them includes watering, fertilizing, pruning, and keeping an eye out for pest and diseases. Pinch off the main stem to make way for lateral shoots, to give it a more compact and bushier look.
If you want large but few flowers, pinch off excess growth, else let all buds bloom. Remove all deadheads after the flowering season is over.
Aster care, as you must have realized, is quite minimal, but what you get in return for this little effort is the enormous pleasures of seeing these blooms, bloom well!