If you cut the heads off of tall Phlox paniculata, often they will send out side shoots to bloom some more. If you cut them down, you will loose out on any of that extra blooming but it probably would not hurt the plants if you want to clean up the garden. It seems a bit early to me, however, to be doing this but whatever. I have never heard of burying the seedheads to get more phlox, as the seeds may not be ripe yet, and then I think they would just rot in the ground. If you cut them off the seeds will not ripen either. Even if they do come up, you are not guaranteed what color you will get as they don't come true from seed. If you want the same color, you should dig and divide your plants and replant where you want them. If you move the small plants now and relocate them, they will probably survive, and grow and may bloom next year if they are old enough to bloom.

thanks, john. i didn't think they came back true to color, and you've confirmed it.
Pat (not the Original Poster)

Thanks. The reason I wanted to cut some down was also for the fact that they have powdery mildew so I wanted to get those out of there. I'll split some I would like to move elsewhere. thank you again.