Fall is Prime Perennial Season

Andrew Bunting

As the days get shorter and cooler, the garden transitions from summer into fall. This period in the garden is highlighted by myriad autumnal colors as green leaves turn to vibrant hues of orange, red and yellow.  

Top: Begonia grandis
Bottom: Aster laevis

Fall is the time when many annuals and perennials come into flower. A common fall plant often purchased at garden centers is the garden mum. While the garden mum provides a burst of vibrant daisy-like flowers, it’s short-lived in a container or garden, often due to insufficient watering or being damaged by cold weather. Most garden mums cannot be effectively planted in the garden as a permanent plant. They’re often purchased and used for a short-season impact in the garden, and then simply discarded in the trash.

There are many fall-blooming perennials that can serve as excellent plants to be sold for more long-term enjoyment. These plants will offer equal “flower power,” have a diverse range of flowering colors in the garden and, most importantly, are hardy and will come back in the garden for years to come.

Fall-blooming perennials can flower in September, October, November and sometimes even into December. Because perennials come back year after year, they’re more sustainable in the garden and cost effective over time. 

Top Fall-Blooming Perennials for Color and Interest
Similar in shape and form to the garden mums are the many flowering asters. The native asters, unfortunately, had a taxonomic revision about 10 years ago, so many of the new genera which were once aster are now hard-to-pronounce genera like symphyotrichum, doellingeria and eurybia. 

Some of the best mum-like options are two selections of the aromatic aster, Symphyotrichum oblongifolium Raydon’s Favorite and October Skies. Usually around the beginning of October, these native asters, which reach about 18-in. tall with an equal spread are covered in lavender-blue, quarter-sized flowers with a yellow center. The plants are completely covered in flowers. Like other late-flowering asters, they provide an important nectar and pollen source. 

Asters are a keystone plant species, which are a host of plants that are most critical for supporting biodiversity in the garden. A little taller in stature is the smooth aster, Symphyotrichum laeve Bluebird. The flowers are comparable to S. oblongifolium, but the form is more upright. A stunning selection of the New England aster is Symphyotrichum novae-angliae Purple Dome. The stature of this aster is very similar to a garden mum. The flowers are a brilliant, saturated purple.

For white flowers in the autumn garden, the Montauk or Nippon daisy for all intents and purposes looks like a Shasta daisy with pure, alabaster white flowers with a golden center. Nipponanthemum nipponicum (syn. Chrysanthemum nipponicum) will reach about 2-ft. tall and flowers in an amazing profusion from September through October. This plant is often associated with maritime climates where it thrives. It also makes an excellent late-season cut flower.

Unique Fall Blooming Perennials
Fall-blooming perennials aren’t limited to only the daisy-like flower plants; there are many others to be considered. Most begonias grown in the garden are showy annuals in pink, red and white, such as the wax begonia or the Rex begonia. Begonia grandis is the hardy begonia. This is a late-flowering perennial begonia with broad leaves that have a beautiful reddish cast on the underside of the leaf. In September, wiry stems rise above the foliage and pendant pink flowers are formed. Once flowering ends, a three-parted pinkish-red seed capsule is formed, bringing extended ornament to the garden. 

The hardy begonia is a spreading perennial, but also populates the garden by seeding. In the spring, new seedlings will serendipitously emerge in the garden. If they seem out-of-place, they can simply be weeded out. There’s also a white form called Alba. Bells and Whistles is a newer introduction with pink flowers and leaves with silver markings. It’s worth noting that Begonia grandis is very late to emerge in the spring. It might appear that the plant is dead, but it’s likely that it hasn’t yet emerged.

Another group of fall-blooming perennials worth considering are the toadlilies, tricyrtis. Sinonome is an excellent selection with orchid-like, skyward-facing flowers spotted with purple. This slowly spreading woodland perennial blooms throughout the fall.

There are many selections of fall-blooming anemones, as well. Commonly called the Japanese anemone or windflower, they’re characterized by basal foliage and tall wire stems that grow to 3- to 4-ft. tall. Anemone x hybrida Honorine Jobert has single white flowers with a yellow center. September Charm has pink petals with white tips and a yellow center. Anemone hupehensis var. japonica Pamina has a bright pink flower. Over time they’ll quickly spread and colonize in the garden, making impactful swaths of color.

Top: Tricyrtis hirta
Bottom: Symphyotrichum oblongifolium Raydon’s Favorite

Care and Design Tips
Fall-flowering perennials can be planted from spring through the fall. After flowering, the plants can be left through the fall and into the winter. Plants can be cut back in the spring. If they need to be cut back earlier for aesthetic reasons, then stack the perennial stems in aesthetically arranged piles. This allows insects that might be harboring in the hollow stems to be able to effectively emerge in the spring.

From a design perspective, fall-blooming perennials combine beautifully with ornamental grasses, shrubs with excellent fall color or autumnal fruiting displays and comparable ornamental trees. 

Combine fall perennials with ornamental grasses for a dynamic contrast in texture and to add graceful motion in the breeze. Create succession plantings by layering early-, mid- and late-season bloomers to ensure continuous color from late summer through fall. Incorporate daisy-type flowers like Montauk daisies for a classic cottage garden aesthetic that feels nostalgic yet fresh.

Together, these combinations provide a vibrant display of color, form and seasonal interest that extends the beauty of your garden well into autumn.

Beyond Mums: Building a Better Fall Garden
Fall-blooming perennials are generally long-lived in the garden and require minimal maintenance from year to year. They’re a great complement to the decor focus of the short-lived garden mum. There are many exciting choices to experiment with in the garden, including fall-blooming aster, the Montauk daisy, hardy begonias, toadlilies and fall-blooming anemones.  

Selecting some native flowering perennials will also add important biological functions to the garden and enhance your garden’s biodiversity. This fall, encourage customers to plant something that will reward them year after year with vibrant color, seasonal interest and lasting impact for both the garden and the environment. GP

Andrew Bunting is the Vice President of Horticulture for the Pennsylvania Horticultural Society (PHS), which uses horticulture to advance the health and well-being of the Greater Philadelphia region. Visit PHSonline.org.