Garden Tasks for Fall (September - November)

Yes, it's getting colder and the daylight is fading, but there is still much to do.

Preparations 

Remove dead and dying stems and foliage from perennials.  Be sure to to leave a few to protect the roots over winter.

Planting

• Plant hardy perennials and hardy evergreen shrubs in early fall.
• Plant deciduous shrubs and trees late in season when leaves have fallen.
• Remove and compost summer annuals.
• Plant spring-flowering biennials and bulbs.

Other Chores

• Transplant deciduous shrubs in late fall.
• Lift and divide hardy perennials.
• Lift and store, or insulate, tender perennials and shrubs before first frost.
• Lift and store dahlias and cannas after the first frosts.
• Take hardwood cuttings of deciduous shrubs.

This list was found in Learn to Garden: A Practical Introduction to Gardening.  I did modify the list a little.