Many gardeners bemoan the coming of fall because they think it means the end of color in the garden. But you don't have to fall into that trap--instead, you can plant a mix of annuals and perennials that bloom in autumn. When you plant them is contingent on the weather, including how much rain or heat you're getting that year. If you're just starting out with fall flowers, ask the staff at a local nursery or extension service for advice on planting times.
Asters are charming fall perennials with starlike flowers ranging from pink to dark purple. Their height varies; tall plants may get up to 4 feet, while smaller varieties don't reach 2 feet. It's a good idea to plant the tall ones about a yard apart and the short ones with at least a foot between plants. Asters enjoy full sun and rich, loamy soil, and they like to stay moist all the time. Many gardeners prefer to plant new varieties because they tend to be more resistant to mildew than older ones.
Gardeners plant the perennial Russian sage for its gray-green leaves and long-lasting spikes of small purple-blue flowers. This plant loves sun and well-draining soil, and it can grow about a yard tall and 2 feet wide. You should water it consistently while the roots are forming, but it needs very little moisture after that--in fact, overwatering may cause it to rot. Some people let sage spread naturally, but others like to stake it for a more upright appearance.
Winter pansies are annuals that provide a blast of color during the fall and beyond. Their flowers tend to be smaller than those of regular pansies, but you still get a spectacular range of tones from rich blue to bright yellow. Choose a spot where they'll get full or partial sunlight, and plant them at least 8 inches apart in loamy soil. Water the pansies well, especially when you first plant them. Cut off flowers once they're past their prime to promote new growth.