Asters are perennial plants with star-shaped flowers that add a splash of late-season color to the garden. There are more than 180 different species of aster to choose from, in shades that include white, pink, purple and red. Asters grow from 8 inches to 8 feet tall, depending on the variety. They prefer full to partial sun and soil that is well-drained. Asters are hardy in USDA zones 4 through 9 and require very little maintenance in order to thrive.
Prepare the planting site by removing all weeds and rocks. Loosen the soil to a depth of 6 inches and amend with a 2-inch layer of compost. Plant the asters 18 inches apart and water until the soil is thoroughly moistened.
Add a 2-inch layer of mulch around the plants to hold in moisture and prevent weed growth. Water the aster plants one to two times per week, depending upon the amount of rainfall received.
Feed once each month with a general purpose fertilizer mixed according to package instructions.
Pinch the top of the asters back 6 to 8 inches in early July. This will promote bushier growth and a longer blooming cycle.
Examine the plants regularly for signs of disease or pest infestation. Asters are especially vulnerable to fungal disease, such as powdery mildew and verticilium wilt. Remove affected plants promptly to prevent the spread of the disease and treat the remaining plants with fungicide.