The leaves fall, the wind blows, and the farm country slowly changes from the summer cottons into its winter wools. ~Henry Beston
Fall is a great time to plant perennials, but make sure the soil temps are above 40 degrees in your area. Once the soil is colder than this on a regular basis the roots will stop growing. Planting now does give them a head start though. You can find some really great bargains out there right now!
Dividing and cutting back-- Hosta flower stalks can be cut back when they are finished blooming. The leaves can be cut back anytime before a heavy frost--after the frost they become mushy. If you prefer to leave them be or run out of time, you can just rake up anything left in the spring. I also transplant mine in the spring and divide them if needed.
Butterfly bushes should be cut back in November before the snow is heavy. In colder zones like ours cut it back to 2 or 3 foot and warmer climates can cut back to a foot or so. Mulching it with straw, hay or grass clippings is good too. Transplant it if necessary in the spring.
Black-eyed Susans: I leave the seeds for the birds, plus they reseed which is fine with me. If you want to cut them back you can do it after the blooms are finished. I also transplant in the spring and very early in the summer and they do well. If you want to reseed them elsewhere in the landscape, just grab a few dried seed heads and sow in the new location, covering lightly with soil.
On OFL we have tips on growing Lords and Ladies this fall for spring bloom:
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