Pretty Purple Flowers Everywhere: Late Summer Asters

By Annie Rzepka, Horticulturist

While we display many different types of asters at the Arboretum, some of our best will be in full bloom in the next month.  You can find New England aster (Symphyotrichum novae-angliae) in the Myrtle S. Holden Wildflower Garden and in the Arlene and Arthur Holden Butterfly Garden.  New England asters make a big impact in the landscape.  They can reach 6 feet tall and are covered with a profusion of purple ray flowers which surround a yellow central disk.  ‘Purple Dome’ is a commonly cultivated variety that can be purchased at many local garden centers.

Fall is great time of year to consider adding plants to the garden that look good and have an ecological landscape function. Plant enthusiasts typically looking to extended late season blooms to prolong color should think about adding some fall blooming perennial asters to their home landscape.
Asters are part of the composite family.  They have daisy like flowers characterized by one central disk surrounded by what looks like many colorful petals.  Despite their relatively simple appearance, the asters are highly evolved plants.  If you think back to your high school botany class, you may remember the parts of a flower.  Most flowers have a ring of sepals on the outside, then a ring of petals surrounding a ring of stamens and the pistil.  Asters are a bit more complex; the sepals are actually modified leaves (think of the scales on an artichoke) and the ‘petals’ which make it appear to be one large flower are actually individual flowers as well. This large flower is called a ray flower.  If you take the time to look closely at the central disk, you will see many, even hundreds of tiny little flowers.  These tiny flowers, called disk flowers, have their own set of sepals, petals, stamens and a pistil.  With all these flowers, there are plenty of opportunities for pollination and for seed production.  Dandelions make up one of the subfamilies of the asters – just think about how many seeds they produce!

According to Mabberley’s Plant-book, there are over 25,000 species of Asters worldwide and numerous tribes associated with the aster subfamily. There are over 2,600 species of aster in North America alone! For butterflies like the painted lady and monarch, asters provide high quality food in the form of nectar.  This food helps give them the energy they need for their long migration journeys.  For those pollinator species that overwinter here in Northeast Ohio, this extra fuel allows them to fatten up and fill their reserves in preparation for a long winter.

Another beautiful late season aster is the aromatic aster (Symphyotrichum oblongifolium).  Cultivars such as ‘Raydon’s Favorite and ‘October Skies’ can be found throughout the Display Garden and in the Rhododendron Discovery Garden. Aromatic asters typically grow 1-2 feet and feature flowers that are about 1 inch wide with violet blue rays and bright yellow central disks.  As the common name suggests, the foliage of this aster is fragrant.

Aromatic and New England asters bloom from September through October and are easily grown in average garden soil in full sun.  They are deer resistant but must be considered a delicacy by rabbits because they do like to nibble on them! (This is not a problem I have observed on a wide scale at the Arboretum but certainly is a possibility.) You can fence your plants if rabbits become a problem or select one of the many natural rabbit repellents available on the market.  So next time you select plants, remember to purchase some late blooming asters!  They will provide great late season interest in your garden and give your local pollinators the boost they need to prepare for the next season.