Great Flowering Plants for the Fall
In the Garden with Andrew
Andrew Bunting. Photo courtesy of the Pennsylvania Horticultural Society.
Today I thought I would walk around Swarthmore to see what interesting perennials are in flower this time of year in the town’s many great residential gardens. Most years, in the Delaware River Valley, we expect good flowering throughout October. Some years, flowering extends well into November.
Fall is for asters, and they come in many types and sizes. In the “good old days,” all asters belonged to the genus Aster. But taxonomists have made many revisions, and the North American native asters have been fractured into many genera.
Great for its bold flowers is Symphyotrichum novae-angliae ‘Purple Dome’. This time of year, they sport a dome of vibrant purple flowers on a plant that can reach 3-4 feet tall. Josh Coceano, Scott Arboretum horticulturist, recently posted to Instagram a picture of S. ‘Alma Potschke’ — an old favorite of mine with stunning cerise flowers. His post showed the aster in combination with the red stems and leaves of the tropical red Abyssinian banana, Ensete ventricosum ‘Maurellii’. The lilac-blue flowers of S. ‘October Skies’ and ‘Raydon’s Favorite’ cover plants that are 2-3 feet tall. Perhaps no other plant has such a stunning profusion of flowers as these two asters. Out front in my gravel garden, I have planted the ground-covering Aster ericoides ‘Snowflurry’, which is covered in tiny white flowers and is great for cascading over rocks or covering the ground.
All over Swarthmore in the fall, you see the native snakeroot, Ageratina altissima (syn. Eupatorium rugosum). Reaching a height of about 2 feet tall, it is covered in white flowers. It can grow well in sun or shade, and it seeds serendipitously here and there.
Another favorite white flowering perennial is the Japanese anemone, Anemone x hybrida ‘Honorine Jobert’. Arising from a rosette of foliage are 3-feet tall wiry stems covered with multi-petaled white flowers with yellow centers. With the slightest breeze, the stems have great movement in the garden.
Symphyotrichum oblongifolium ‘Raydon’s Favorite’ has a stunning profusion of flowers. Photo: Andrew Bunting
Tonight, I saw a fall-flowering bulb growing in the front of Charles Cresson’s Hedgleigh Spring. Sternbergia lutea, commonly called the autumn daffodil, looks somewhat like a daffodil and somewhat like a crocus. The intense golden-yellow flowers are great for massing under shrubs.
I love the ironweeds, Vernonia. Some of the species can tower to over 12 feet tall, but others are more diminutive and suitable for most gardens. Vernonia lettermannii ‘Iron Butterfly’ has very fine foliage, as well as an abundance of small purple flowers in the autumn. The green foliage ultimately turns golden-yellow and has a similar impact in the garden as the thread-leaf bluestar, Amsonia hubrictii.
As you drive along roadsides or look into meadows or pastures this time of year, you often see many species of goldenrod, Solidago. A popular cultivar with cascading sprays of flowers is the aptly named ‘Fireworks’. It combines beautifully with another fall-blooming plant, Sedum ‘Autumn Joy’, which has burgundy flat-topped clusters of flowers.
Another great perennial with an amazing cascading effect in the garden is Lespedeza thunbergii ‘Gibraltar’. This perennial member of the pea family can grow to 5-6 feet tall. In mid-October, the foliage is festooned with small vibrant pink flowers.
There are many other great perennials to consider for fall, including the toad lilies, Tricyrtis; Russian sage, Perovskia; and even a hosta with very late lilac flowers, Hosta tardiflora.
Happy gardening!
Andrew Bunting
Reader Questions:
Q: I’d like a refresher on when and how to divide daylilies, including tips for actually cutting through the clump.
A: The easiest time to divide daylilies is the early spring right before they emerge or as they are emerging. You can simply dig up a clump and cut it into smaller chunks and replant. It will seem brutal, but the daylilies will not skip a beat.
I cut the clumps with a spade or shovel.
Q: I wonder about dividing Siberian irises — when and how. By the time I think about doing it, it’s really hard to manage those clumps.
A: For Siberian iris, you can follow the exact same approach as for daylilies. Early spring, in general, is the best time to divide most perennials.
Send your gardening questions to editor@swarthmorean.com.
Andrew Bunting is vice president of public horticulture at the Pennsylvania Horticultural Society and vice president of the Swarthmore Horticultural Society.
