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Backyard Gardener: Fall asters for autumn color

Hello Mid-Ohio Valley farmers and gardeners. After a few days of extreme heat and humidity, fall weather is finally here. The plentiful rains provide a great opportunity for fall planting of trees, shrubs, flowers and vegetables. Get those plants in the ground as soon as possible so they can establish a good root system before winter arrives.

This week I want to discuss fall asters. I know, the chrysanthemum is the go-to flower for fall and with good reason. However, we need some variety in plants and colors. Look no further than the fall aster.

Fall asters can be a great addition to flower beds and gardens. When we think of fall flowers, mums are the king, but asters can provide a diversity of autumn color to stretch out until winter arrives. They come in a range of colors from red to purple, bluish to white, and provide a nice complement to the colors of fall mums.

Furthermore, asters are a late-blooming plant which provides food for pollinators, especially the honeybee. Asters and goldenrod can be major sources of fall nourishment for our native pollinators before the cold winds of winter set in. So, if you are planting a pollinator garden you definitely need to include this native flower.

Fall asters will begin to bloom when the days get shorter in late summer to early fall. Their general range in bloom time is from early September to late October, with a particular species or cultivar usually blooming for two or three weeks or longer. They are short-day plants, similar to mums, meaning they need long periods of darkness to initiate flower buds.

The asters (Asteraceae) are an enormous family of flowering plants. Daisies, sunflowers, zinnias, marigolds, and more are all grouped together in this category. Most aster species can be recognized by their composite flowers. Composite flowers are made up of hundreds of tiny flowers, with disk flowers at the center and ray flowers around the edges.

Fall aster varieties can be broken down into several types, including the New England aster, (Symphyotrichum novaeangliae), the aromatic aster, (Symphyotrichum oblongifolium) and the New York (Aster novi-belgii).

There are thousands of varieties of asters to select from. Many are native to West Virginia and the Eastern U.S. It may get a bit confusing, but asters native to North America and native to Europe are classified differently. Most Eastern North American aster species belong to two genera, Symphyotrichum and Eurybia.

Purple is a very common color identified with asters, probably due to them being the first varieties grown in the U.S. in New England. However, there are many varieties to choose from. As I stated earlier, these daisy-like flowers range in color from purple, white, pink, and red, all with bright yellow centers.

Varieties may vary in height from six inches to six feet. Taller varieties can be pruned back by a third several times throughout the summer, stopping in late July, to create a more compact plant. This will also increase the number of blooms on the plant.

“Purple Dome” is a popular choice. It is a New England type aster that blooms in early fall with hundreds of deep lavender-purple flowers. This dwarf plant (12-24 inches tall) has a neat mounding habit and is a perfect choice to edge pathways and fill small spaces.

The aromatic aster, “October Skies,” is also a good pick. Aromatic purple to lavender-blue flowers with yellow centers create dazzling purple mounds in the fall. The blooms make good cut flowers and are attractive to butterflies.

The plant is easily grown in average, dry-to-medium, well-drained soil in full sun, but it also does well in sandy or clay soils and can withstand drought. It slowly colonizes by stolons, and regular thinning can help control its spread.

Although many asters like drier conditions, the swamp or purple-stemmed aster can be planted in wet areas. It is native to the eastern U.S. and has a long bloom period (August-November) with many light-violet or violet-blue rays surrounding yellow centers. It has bristly, purplish stems and toothed, glossy, lance-shaped leaves. This aster is a stout plant growing 4-8 feet tall.

Calico aster (lateriflorus horizontalis), named from the appearance of its many tiny pink and white flowers, is a species reaching one to two feet. Unlike most asters, stems of this species are arranged in horizontal layers giving rise to another common name, horizontal aster.

Aster variety trials (56 varieties tested) were held from 2003-2006 at the Mt. Cuba Research Center in Hockessin, Del. Results can be found at mtcubacenter.org.

Home gardeners can manage asters as you would other perennials. The good news is they tend to be low maintenance plants and are very hardy, thriving even in drought conditions. They grow best in full sun to partial shade areas with well-drained soils.

Plant at least one foot apart for the shorter varieties, three feet apart for the taller ones. Some light fertilizer such as one-fourth to one-half cup of an organic fertilizer early in the season will help.

Although they are considered perennials here in the valley, they need to be planted at least six weeks before it freezes to develop a good root system and overwinter successfully. Cut the plants back to about two inches above ground level after the first hard frost has turned the foliage brown to prevent plants from self-seeding and spreading.

You may choose to allow plants to develop seeds for the birds to enjoy. Divide the plants in early spring every two to three years, or when the center dies out to keep fall asters healthy. Some varieties are unfortunately prone to powdery mildew, which can be reduced with good air circulation and watering in the morning at the base of the plant.

Again, fall blooming aster are a major food source for pollinators. They also serve as the larval host plant for several butterflies and moths, including painted lady butterflies. Asters also make great cut flowers for mixed fall arrangements. Arrange them with bright yellow goldenrod and ornamental grasses for a stunning fall decorative display.

Contact me with questions at the WVU Extension Office at 304 424 1960 or at jj.barrett@mail.wvu.edu. Good Luck and Happy Gardening!

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