Extension Educator, Horticulture
Don't neglect the late bloomers: flowers that are content to stay in the background while the other floozies flaunt their frills far ahead of fall. Just as most flowers are frying or fading, the late blooming perennials take off and steal the show.
Fall Anemones which include an array of species (Anemone hupehensis, A. x hybrida, A. tomentosa, A. vitifolia) are reliable late bloomers. Some start blooming in July and continue to bloom into November. Fall Anemones prefer moist well-drained soils in a garden shaded from late afternoon sun. They can take full sun if given plenty of moisture.
Anemones have dark green leaves with 2 to 3-inch diameter flowers held high on delicate wiry stems. Colors range from pure white to pink or purple. Flowers may be single to semi-double or double-petaled. The cultivar 'Margarete' has semi-double flowers of striking pink with yellow centers. At three feet tall it's an amiable choice for backgrounds. A 150 year old cultivar 'Honorine Jobert' has white single-petaled flowers offering a stunning contrast to the dark green leaves. 'September Charm' has single rose pink flowers. 'Robustissima' with mauve-pink flowers can be too robust in a shady garden. It's best in full sun where it's not so vigorous.
In trials at Chicago Botanic Gardens the three highest rated fall anemone varieties were cultivars of Anemone x hybrida: 'Andrea Atkinson', 'Max Vogel' and 'Serenade'. 'Andrea Atkinson' grows to nearly 3 feet tall with white flowers and creamy yellow centers. 'Max Vogel' and 'Serenade' have similar pink flowers with yellow, globe-like centers. Both selections have bloom periods of more than two months. Their vigorous growth and strong stalks make them less susceptible to flopping. 'Max Vogel' is about 3-4 feet tall with an upright, clumped habit. 'Serenade' at 24 inches tall could be a good choice as a ground cover.
Fall Asters come in a wide range of colors and sizes, however, not all asters bloom in fall. Numerous species of asters are in the trade and many are native to North America. Most asters prefer full sun and may need a good pinch of the stems a couple times a season to keep them from getting too lanky. 'Purple Dome' is a particularly nice rounded aster with deep purple flowers.
A few lesser known asters include Heath Aster and Calico Aster. Heath Aster, Aster ericoides has numerous tiny white, pink or blue flowers similar to baby's breath on 3-foot tall plants.
The Calico Aster, Aster lateriflorus var. horizontalis is almost a shrub. The small white flowers with red centers are borne on many horizontal stems for a stunning midnight show.
Russian Sage, Perovskia atriplicifolia, is not a culinary sage but a beautiful three to four feet tall background plant for a sunny border. The spikes of long lasting blue flowers on silvery stems are a nice contrast with the other late bloomers in the garden. The leaves are small and silvery green. When crushed the leaves smell "like the feet of Russian soldiers" but fortunately their placement in the back of the flower border protects our noses from assault. Russian Sage starts blooming in mid-summer and continues well into fall. Full sun is a must as is well-drained soil. Sometimes Russian Sage flops. Be sure to cut back to about 6 inches in the spring. Plants can also have 4-5 inches removed by pinching when the plants are about 12 inches tall. 'Blue Spire' has deep blue flowers. 'Longin' has a narrow upright habit.
Remember to add late bloomers for a late season flower show.