Unlike annuals, which are mainly purchased in the Spring and early Summer and only last for one season, perennials are best planted in the Fall. Autumn planting gives the plants time to get settled in, grow roots and be ready to go in the Spring.
Many times, gardeners, especially new ones, buy their plants in the spring when they are in bloom. And often times these plants have been grown in warmer climates and shipped North so they are in bloom when they hit the garden centers. They may have also been treated with growth hormones to force them into bloom.
When the gardener gets them home and transplants them, they are often disappointed that the plant wilts and the blooms fade and die quickly. This is due to transplant shock. The plant senses that something has changed and goes into a survival mode to grow roots, the result is the plant shuts down the blooms and puts it’s energy into growing the roots necessary for it’s survival.
Planting perennials in the fall avoids this disappointment. The plant still experiences an amount of transplant shock, but due to the cooler and wetter Autumn climate, the amount of shock is lessened. Also since the plant doesn’t have blooms to support, all of it’s energy can be put into growing roots and getting ready for next spring.
Trees and shrubs can be transplanted right up until the ground freezes. Other perennials will benefit from the warmer ground temperatures of early Autumn.
Your new plants will still need to be watered if we experience a dry Autumn, but fertilizing them should be delayed until the next spring, you don’t want to encourage new growth when the plant is about to enter dormancy for the winter.