Answer: Black-eyed Susans will bloom naturally over a long period, but if you deadhead the plants by cutting them back by about half once the main flush begins to fade, you may stimulate another (smaller) flush of bloom in the fall. Some gardeners simply allow the seedheads to remain and consider them an attractive fall and winter feature in and of themselves, and the birds will enjoy the seeds. The plants would then be trimmed back very short in the spring.
Tall phlox will bloom over a longer period if spent flowers are removed one by one. In general, phlox (except creeping phlox) should be trimmed off very short in the fall once frost has browned the tops. All of these plants will give their best display in full sun with rich soil that is kept evenly moist (but not soggy).
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