How to Care for an Aster

Care for your asters with some basic rules of thumb, and be rewarded with spectacular blossoms in a variety of colors. Planting these wonderful stars (aster is Greek for star) will uplift and brighten your fall garden. This Michaelmas daisy (another name for the flower) produces blue, white, red, purple, pink and lavender flowers. Ranging from 8 inches to almost 8 feet, these flowers make good border plants, but be careful of mildew diseases that attack them.

Propagating Asters

Asters can be grown indoors or may be sown into the garden directly (providing danger of frost is well past). Plant them in early spring, preparing gardens with a tiller to loosen soil. Sow the seeds approximately 1 foot deep into a mixture of compost and garden soil. Germination usually occurs after approximately 1 month.

Plant in well-drained, moist soil in either partial shade or morning sun. Some varieties can be planted in full sun, but this varies, so be sure to check planting instructions. Compost, peat moss or mulch will retain moisture, control weeds and ensure plants have sufficient nutrients.

Your hole for transplanting asters should be twice as wide and deep as the plant's container. Plant the crown of the aster even with the ground level. Plant and thin plants to at least 18 inches apart to avoid overcrowding

Caring for Asters

Divide mature plants in spring, just as the new shoots begin to grow. This should be done every few years to avoid crowding of plants.

As with many other flowering plants, dead head (cut back spent flowers) to make room for newer blossoms. This will extend the health and flowering of your plants. Be sure to dead head early on in the blooming season. Blooming will be reduced if done too late. This will also restrain unwanted reseeding which will cause plant overcrowding.

TIP: Our expert gardening advisor, Karen Thurber adds, "To produce a fuller, shorter plant, that requires less staking, pinch your asters when they reach 10 to 12 inches. The first pinch should remove 5 to 6 inches and leave 3to 5 internodes. Asters can be pinched 2to 3 times during the growing season, with your last pinch before July 25th. A pinch later than July 25th will delay flowering."

Remember, asters are prone to mildew so be careful to plant them in areas with good circulation and good sun exposure.

As with other flowering plants, do not allow water to saturate leaves. Be sure to water at the plant's roots to prevent mildew and mold. Drip irrigation and utilization of a soaker hose work very well in watering these plants.


In addition to accenting rock gardens, grow your asters in succession, so that have an ongoing blooming season. Planting asters will also deter some insects in your garden. Plant them throughout your garden to limit pesticide use.

Asters attract butterflies, which will enhance the beauty of your garden.

Unlike marigolds and similar plants, aster seedlings are unlike the parent plant and may not be desirable to allow to reproduce. Remove the flower stems before they set seed to prevent this cycle from occurring.

Water asters as directed, but remember that they are considered a "drought tolerant" plant and do not like standing water.