Asters produce large clusters of delicate daisy-like flowers in white, purple, lavender, pink or red. They are at times mistaken for daisies, especially the white ones. They grow in abundance and love full sun.
Asters can be planted under full sun, which is by far the best spot. They can tolerate a little early morning shade, but too much shade will bring on the powdery mildew.
Use a fertile loam that is well drained but can retain adequate moisture. Clay soils are not preferred as they hold the winter water and the roots will rot. Sown aster seeds at least 18 inches apart.
If there are prolonged dry spells during the growing season, give extra water to the plants to keep them turgid. If they wilt or die back from lack of water, they will recover fully after a heavy rainfall or will become dormant until the following season.
Young plants need to have sufficient water to become established but they should not be watered once they are growing satisfactorily, except in very dry weather. Add irrigation tubing planting areas if you live in regions where summer drought is normal.
Mature clumps will need to be divided every three to four years in the early spring or late fall after the flowering has finished. When shoots have reached one-third of their final height, pinch out the top 1 to 2 inches (2.4 to 5 cm) to promote bushier growth and to prolong the fall bloom.
If soil has been thoroughly prepared before planting, few perennials require more than an annual top-dressing of a balanced slow-release fertilizer, preferably applied in early spring after rain.
Plant bugs, earwigs and slugs are common problems.