Late Blooming Annual Flowers
In late September two annual flowers stand out for their late season performance: begonias and impatiens. Beds and baskets are still in full bloom. Others, like marigolds and geraniums still have a moderate amount of bloom. Petunias only have a few scattered flowers. This is a good thing to remember when you are planting beds and baskets next spring.
Why do some annual flowers continue to bloom later in the season? My guess is it is largely due to day length. Most annual flowers are “long day plants” Their flowering is triggered by the long days of late spring and summer. When the days become as short or shorter than the nights, they quit blooming. Impatiens and begonias are apparently “day neutral plants”. Day length does not affect their flower formation.
We are familiar with “short day plants” such as chrysanthemums and perennial asters which begin blooming as the days get shorter in the fall.
So if you want more color this time of year, plant more begonias and impatiens