Here's a quick overview of fall-blooming perennials that are hardy in our Northern Minnesota zone. Plan now for fall color!
Aster (Michaelmas Daisy)
Asters are the respected standby for all fall-blooming gardens. They are most familiar in purple shades but also bloom white, pink, and blue. Their fine-petaled flowers are between half an inch and two inches across.
Asters begin to bloom in August and continue until frost. Pinch the tops in early summer to promote bushy growth and dozens of flowers. Asters like to creep through the perennial garden but they blend nicely with other flowers.
The chelone is a joy in the perennial garden. It stays put without invading its neighbors, grows in a dense mound, and blooms red, pink, or white. The flowers are indeed shaped like turtle heads and the fine leaves look great before blooming sets in.
Partial shade is OK for chelone, and protect from excessive heat if planted in full sun. Keep well watered. Divide chelone every three years in the spring.
Choose hardy mums for the perennial garden. In Northern Minnesota, many mums are grown as annuals. Transplant as early as possible so they have time to establish good root systems. Mums bloom in almost every color, can be tall or short, and generally keep to themselves without spreading.
It's very important to mulch hardy mums heavily after first frost to protect them from our harsh winters. Water well, give them full sun, and they'll be reliable fall bloomers for many years.
Eupatorium (Joe Pye Weed)
Eupatorium is a native plant that does extremely well in northern perennial gardens. They tend to grow tall so plant at the back of the bed to provide structure. The plants have a dense appearance with typically purple flowers and look nice all summer before blooming really gets going.
Joe Pye Weed is an adaptable plant that doesn't mind being a little dry or growing in poorer soils. It's absolutely perfect in cottage-style gardens.Formal-style gardeners may not like its weedy appearance.
Heliopsis (False Sunflower)
Heliopsis blooms small, happy yellow flowers. It begins a little earlier than most fall-blooming perennials and continues for weeks until first frost. Plant in masses for best effect (three or more plants in a group).
False Sunflower stems tend to be fine and somewhat fragile, so grow this plant in a perennial cage to help it stand up. If you like, allow the plants to trail on the ground. Some varieties are lower-growing on sturdier stems so they flop less.
Sedums are awesome. Their foliage is deeply colored from lemon yellow to deep green and they bloom profusions of flowers later in the season. The Autumn Joy variety is perhaps the finest example of the sedum.
These plants tend to spread slowly through the garden and require minimal attention. Water occasionally if there's been a dry spell, but otherwise you can leave sedums alone and they'll thrive. They look best when interplanted with each other so foliage can contrast.