Late August to September is aster blooming time. Most grow well in USDA zones 4 - 8 in dark purple, light purple, blue, and pink. Choose 'Purple Dome' for instant colour. While many asters grow 3-4 feet tall, 'Alert' grows only a foot. If you don't want asters to self-sow, cut off the seed heads after they bloom.
Goldenrod (Solidago sp.) has become popular. Many varieties of this perennial add gold to the fall garden and provide nectar for pollinators. Most goldenrods grow in USDA zones 4-8. 'Fireworks' is a 3-foot-tall variety. Cincinnati Zoo & Botanical Garden recently selected 'Solar Cascade' Most goldenrods spread by underground rhizomes and are easy to pull out.
Mums can be grown as perennials in the garden or in containers in the fall. Some, like the 'Igloo' series, can survive in USDA zones 3 - 4. Mums in the garden are looser and taller than in pots. They thrive in full sun and add fall colour.
Tall sedum prefers dry, sunny spots. Hylotelephium plants grow one to two feet tall and produce star-shaped flowers. Many still call them Sedum. They also attract pollinators. 'Autumn Joy' is a classic. Tall sedums are hardy in USDA zones 4-9. Leaving the seed heads alone gives winter interest.
Japanese anemones, also called windflowers, are perennials that thrive in partial shade and well-drained soil. Once established, they can take over an area. 'Honorine Jobert' is 4 feet tall with white flowers. 'Robustissima' blooms pink. 'Prince Henry' adds bright pink to fall gardens.
Fall colchicum flowers will make your neighbours think you have magical gardening powers. Colchicums' spring foliage dies by midsummer. Mid-fall, purple, pink, and white flowers bloom, making your fall garden look like spring. Colchicums need well-drained soil and full or partial shade. Immediately plant bulbs. Divide and share spring clumps.
Boltonia is called false aster because it resembles asters. It grows 5-6 feet tall and blooms in August-September like asters. Full sun and well-drained soil are ideal. White flowers bloom in USDA zones 3-10. Popular variety: 'Snowbank' Fall pruning prevents self-sowing.
Oxblood lily, Rhodophiala bifida, is hardy in USDA zones 7 - 10 and blooms in early fall, when schools start. These flowers, introduced by German settlers, are common in older gardens in central Texas. After blooming, the foliage lasts through winter and spring/summer. Oxblood lilies like full sun and well-drained soil.
Try Eutrochium purpureum for a tall flower in a sunny border. Joe Pye weed grows 7 feet tall in USDA zones 4-9. It likes shade and wet soil. If Joe Pye weed is too tall, plant Eutrochium dubium, 'Little Joe' Both have fall mauve flowers that attract pollinators.
Joe Pye Weed