Dividing An Aster: How and Why

The aster is a genus of the family Asteraceae, native to Europe and North America, that contains hundreds of species. They're known for their small white, pink, red or lavender daisy-like flowers that grow in clumps from 6 inches to 7 feet tall. Asters are commonly grown for their fall blooms that keep gardens colorful past the summer months, often through October. 

Dividing Asters

Dividing plants is the process of taking one grown plant and breaking them apart to form 2 or more "new" plants. Many perennials should be divided for best results; the aster is one of these. Divide perennial asters every other year in the spring. Dividing in the fall will not give your aster enough time to settle in before the frost, and dividing in the summer may result in no blooms, because the summer heat is too much of a shock for them.

Step 1: Dig Up the Aster

Using a shovel, press several inches into the ground all around the plant. Keep the blade a few inches away from the plant. Once you have cut all the way around, use the shovel as a lever, lifting the plant out of the soil. 

Step 2: Divide Aster in Half

Take the aster in your hands and shake off the soil from the roots. Divide by cutting your aster in half with a spade or shovel. Some people discard the very center of the plant, as the outside tends to be healthier. Remove any dead or withering leaves and stems.

Step 3: Replant the Aster

Dig a hole slightly larger than the size of the roots and replant. Be sure to replant in well-drained soil and in an area that receives at least 6 hours of sun a day. If you are living in USDA zones 7 to 9, asters can tolerate partial shade. Plant the two "new" asters at least 18 inches apart, since they grow out in clumps. Water immediately and keep watering generously throughout the growing season.

Why Divide?

Asters should be divided every other year for a number of reasons.

  • It controls the size. Asters are fast growers, and they can look scraggly and out-of-control if not divided regularly.
  • Dividing will produce a tighter, bushier and healthier looking clump.
  • It keeps them fresh and and sprightly-looking.
  • It may decrease the size, but it increases the quality.
  • Dividing increases your numbers. When you find an aster that you love, don't buy another one; just divide in half. 

Follow these guidelines for dividing asters, and you will have multitude of new and improved versions of your favorite flowers.