Temperatures are dropping and the days are getting shorter, but that doesn’t mean that you can’t still enjoy some flowers in your landscape — you just have to choose the right ones. In Kansas City, the first frost comes in mid to late October, but asters can survive light frost to provide your landscape with colorful, daisy-like flowers for weeks after your other garden standbys have called it quits. Asters can be a real star in the fall garden, and they’ll reward you by coming back year after year.
Growing Zones: 3-8, depending on variety
Bloom Time: Late summer through late fall
Exposure: Full sun
Mature Size: 1 to 8 feet in height and 1 to 4 feet in diameter, depending on variety
Notes: Asters look like small daisies with yellow centers and finely cut petals. Flowers come in a range of colors, including white, pink, purple and blue. Asters are native to the U.S. and work equally well in mixed wildflower gardens and formal borders.
Growing Asters in the Landscape
Asters come in a wide range of colors and sizes, so consider the variety carefully before deciding where to plant your garden. Their yellow centers make them a nice companion plant for yellow goldenrod and hardy chrysanthemums for an autumn garden, but take their mature height into consideration before you decide whether to plant them at the front or back of the border. Bees and butterflies often flock to asters for a late-season food source.
Plant your asters in a location that receives full sun and has soil that drains well. Average fertility is fine, but heavy clay soil should be amended with compost to aerate and improve drainage. Likewise, very sandy soil will benefit from moisture-retaining compost as well.
Once soil is amended, you can plant asters any time after frost and even up until very early fall. If you plant them after late summer, sprinkle a bit of bone meal in the hole before planting to help roots get well established before winter. It’s easiest to plant aster from transplants, so dig a hole a bit larger than the potted root ball and place the transplant at the same depth it was in its pot. Backfill soil and make sure it is firm around the edges so you can press the plant into place. Water well.
Ongoing Care for Asters
Water your asters regularly for their first season until they are established. After that, these plants need about an inch of rain per week, and perhaps more during very hot summer weather. Asters don’t require much fertilizer to grow well; a layer of compost spread around the roots as a mulch in early spring will serve well to both feed the plant and keep out weeds for the summer.
After three or four years, your asters may need to be dug up and divided to improve vigor or to keep happy plants from becoming too large for their space. This is best done after your last frost but before the plant puts on too much green growth. Dividing plants early will make them easier to handle and will allow the roots more time to establish when you re-plant them.