Asters - Garden Basics - Flower - Annual

By Josie Borlongan, Garden Guides Contributor

About Asters

Asters are from a genus of flowering plants in the family Asteraceae. They are perennial plants that can be divided. The name Aster comes from the Ancient Greek word astron, meaning star, which describes the shapes of the flowers.

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.

Site Preparation

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.

Choosing a Variety

Some common Aster species are: Aster alpinus (Alpine Aster, which flowers in summer, 8 to 12 inches tall, single flowers); Aster amellus (European Michaelmas Daisy or Italian Aster, flowers in early fall, 24 inches tall, single in clusters); Aster divaricatus (summer bloomer, 12 to 24 inches, cluster bloomer); Aster lateriflorus (Lady in Black); Aster linosyris (Goldilocks Aster); Aster pringlei; Aster scaber; Aster sibericus; Aster tataricus; Tatarian Aster (a late fall bloomer, 36 to 60" tall cluster); Aster tongolensis (a summer bloomer, 18" tall, single blooms) and Aster tripolium (Sea Aster).


Sown aster seeds at least 18 inches apart.

For container-grown asters, first dig a planting hole. Then water the plant thoroughly and remove it from its container, taking care not to damage the roots. To help the plant establish quickly, carefully loosen the sides and base of the root ball, particularly if root bound, by teasing out the roots with your fingers or a hand fork. Plant asters at ground level depth so that the crown of the plant is level with the surrounding soil. Then aback fill with soil and loosen the surface of the soil with a hand fork and water thoroughly.

Plant bare-root aster plants immediately after purchase to avoid dehydration.


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.

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