Guide To Growing Asters for Fall Flowers

A highlight of autumn in my garden is seeing the purple, pink, and almost blue flowers of fall asters. They bloom later in the season and are often covered with butterflies and bees.

In my garden, they’re at their peak toward the end of September. I especially like when an unexpected seedling hidden among other perennials reveals itself by flowering when most are done for the season.

What Are Fall Asters?

Fall asters are native perennials that bloom late in the year, usually after Labor Day. Though recently given the tongue-twisting botanical genus name Symphyotrichum, everyone still calls them asters.

They’re also commonly called New England asters or Michaelmas daisies, the latter because they’re often blooming on the September 29, the Christian feast day of St. Michael the Archangel.

Types of Fall Asters to Grow

Most asters are hardy in U.S. Department of Agriculture Plant Hardiness Zones 4 through 8. They come in several sizes and colors. Some popular types of fall asters include:

• ‘Purple Dome‘: Hardy in Zones 4 through 9, it grows just two feet tall and wide with dark purple flowers.
• ‘Raydon’s Favorite‘: Hardy in Zones 3 through 8, it grows three feet tall. Flowers are lavender blue.
• ‘Alma Potschke‘: Hardy in Zones 4 through 8, it grows up to four feet tall. Flowers are dark pink.
• Smooth Aster: Hardy in Zones 4 through 8, it grows up to 3 feet tall. Flowers are almost blue.
• Wood’s Asters: Hardy in Zones 4 through 8, it grows just a foot tall and two feet wide. Varieties are available with blue, pink or purple flowers.

Should You Buy Plants or Sow Seeds for Fall Asters?

Fall asters are most often sold as plants. You can often find them at a local garden center in fall when they’re in flower. You may also find the plants in spring, but they won’t have flowers yet.

Asters aren’t often grown from seeds. Many seeds sold as “asters” are not the fall asters, but summer-blooming annuals that look like asters.

How To Grow Fall Asters

Once established, fall asters don’t require a lot of extra care.

Planting

Fall asters grow best in full sun to part shade in well-draining soil.

To plant an aster, dig a hole the same depth as the container the aster is growing in, and slightly wider. Pop the aster out of its container, spread the roots out a bit (especially if the plant has been in the container a while), place it in the hole and backfill with the soil you’ve dug out. Tamp down the soil around the plant and water it well.

You can plant asters at any time. If planting in fall, do so at least six to eight weeks before your first frost. This gives the plant time to become established before it gets too cold.

Watering

Fall asters don’t usually need extra watering. Once established, they’ll withstand periods of dryness in the summer. When newly planted, water once a week if you don’t get rain.

Fertilizing

In most cases, fall asters won’t need fertilizer. A layer of compost around the plants adds soil nutrients.

Dividing

Fall asters will continue to grow out from the center of the plant each year. That sometimes creates a donut effect, with the center becoming bare. If this happens, dig up the aster, divide it into sections with a sharp knife or shovel, and replant the sections.

Digging and dividing will often give you extra plants to share with others or plant elsewhere in your garden.

Deadheading

Fall asters don’t have to be deadheaded, but cutting back spent blooms in early winter keeps them from self-sowing in the garden.

Many gardeners, including me, will cut back fall asters in late spring to encourage branching and more blooms in the fall. To do this, cut each stem a few inches in late spring, then repeat a month or so later. Don’t cut back stems after mid-summer (around July 4) or you may be cutting off flower buds.