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Growing Tips: Asters for the Autumn garden

PHOTO PROVIDED Asters form a cloud of fall color in this Clinton County garden.

When thinking of fall, shades of yellow, orange, red, and brown often come to mind.

Bright orange pumpkins, chrysanthemums in hues of gold, rust, red, and pink, and golden corn stalks seem to be everywhere. Central Pennsylvania’s trees and forests are awash in these warm colors, creating a truly beautiful display. Visitors often drive for miles just to take it all in.

As attractive as they are, I have to admit that these warm colors are not my favorites. I prefer a cooler palette that includes plenty of blues, purples and greens. That preference is reflected in the flowers that bloom in my gardens at this time of year. While I have plenty of hardy chrysanthemums and numerous trees and shrubs displaying their warm fall colors, I’ve made it a point to incorporate some cool colors into my autumn landscape. To do this I turned to hardy, fall-blooming asters.

The aster family (Asteraceae) is a big one, and contains several members which are native to Pennsylvania, including Smooth Aster (Symphyotrichum laeve), New England Aster (Symphyotrichum novae-angliae), and New York Aster (Symphyotrichum novi-belgii). These native asters are a source of nectar and pollen for adult bees and butterflies and their foliage provides food for their larvae. Numerous cultivated varieties of asters have been developed to meet preferences for height, color, form and bloom season, giving gardeners plenty of choices.

To begin incorporating blue shades, I choose a cultivar of the native Smooth Aster called “Bluebird”. This very attractive plant has bluish-green leaves and produces an abundance of blue-violet flowers with yellow centers. It reaches a height of three to four feet and is a reliable, prolific, late season bloomer. It does best in full sun and prefers dry soil.

I placed several of these plants at the back of a sunny border and planted shorter chrysanthemums in a variety of warm colors in front of them to create a contrast. I’m happy to say that this year’s drought didn’t seem to bother them at all.

I selected Aster oblongifolium “October Skies” for the front of a different border because it only reaches a height of about eighteen inches. It prefers a sunny location, is drought tolerant and forms bushy bright green mounds approximately 18 inches wide which are cloaked in blue-lavender flowers in fall. Aster oblongifolium is commonly called aromatic aster because its stems, when cut or crushed, are fragrant.

I was so pleased with the appearance of both “Bluebird” and “October Skies” that I decided to try some of them in a bed of their own. When in full bloom, the foliage is nearly obscured by the profusion of blooms and this bed looks like a blue-violet cloud of flowers.

To introduce some deep purple shades, I choose “Purple Dome,” a New England Aster cultivar that produces rich purple flowers on strong stems. The bushy plants create mounds approximately 18 inches tall and two feet wide. Their height makes them a good mid-border plant and they contrast very well with chrysanthemums in shades of gold, yellow and orange.

While these fall-blooming asters have certainly added to the beauty of my gardens, they have another very important role. They provide pollen and nectar for bees and butterflies late in the season when other sources are becoming scarce. It’s been several years since I decided to expand the color palette of my fall gardens to include blues, purples, and greens and I am happy with the results. In fact, those cool colors seem to enhance my appreciation of the warm orange, yellow, and red flowers and foliage that are so much a part of autumn in Central Pennsylvania.

More detailed information on asters and the many cultivars that have been developed is available from the Chicago Botanic Garden at https://www.chicagobotanic.org/downloads/planteval–notes/no36–asters.pdf and the University of Vermont at http://pss.uvm.edu/pss123/peraster.html.

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Debra Burrows, PhD, is a retired Penn State Extension educator and coordinator for the Clinton County Master Gardeners. She can be reached at dcb3@psu.edu.

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