Gardeners who want to have flowers in bloom during September have to make plans early in the year. A careful mix of annuals and perennials can keep the beds colourful no matter if the month is a hot one or if it is a cool wet introduction to fall.
The August garden probably featured a lot of tender annuals like marigold and zinnias that love heat and can tolerate long periods without rain. However, September can be a lot cooler, especially at night. So, if you want to have a lot of colour in the garden, you must plan and plant for it in the spring. Start with the late blooming perennials.
September is when the chrysanthemums begin to bloom, if you have kept the buds pruned off until after July 4th. These perennials clump like small bushes and tend to have flowers that are straw coloured, brown, purple, gold or white. Other perennials that bloom with similar colours in September are asters. Monkshood, hardy ageratum and Japanese anemone are additonal late blooming perennials. Once these plants are established in your garden, they will continue to bloom year after year.
Another category of plants that bloom in September are the annuals that must be planted each year and can tolerate the cooler nights. They include pansies, calendula and sweet alyssum. Snapdragons, which have been blooming all summer, will continue to bloom in September as long as you keep them dead headed. Petunias and dahlias will also continue to bloom into Autumn if they are kept picked.
Surprisingly, roses that had their first bloom in the late spring, will put out many new flowers during September and into the late fall. The secret to having fall roses is to pick the blossoms as soon as they finish blooming and before they can form rose hips. Like any plant, once the seeds have developed, the plant has no more need to bloom.
If your garden has a lot of shade, plants like impatiens and hosta will thrive all summer long especially if you keep them well watered. These shade loving plants will continue to bloom into September. Hosta, a perennial will come up year after year. If you take some cutting of the impatiens before the first frost, you can root them in water and replant them in the garden in the late spring.
September is also the time to plant spring flowering bulbs like daffodils, crocus, hyacinths and tulips. Dig up the bulbs that cannot tolerate a freeze. These include gladiolas, canna lilies and begonias. You can replant them in the late spring. Finally, if your peonies have not been divided for 3 to 5 years, September is the time to do that job as well.