If they have four petals then they are dames rocket - a prolific self seeding plant/pest (depending upon your point of view) If five petals then it is probably phlox. If it is dames rocket, then they have shallow root systems and can be transplanted anytime. If you do so while blooming, it will probably die back until next year.

Hi Shari. Good call. You were absolutly correct. That's what they are! They looked like phlox to me but as you said they are Dame's Rocket - Hesperis Matronalis. I may try them in a contained spot. They are quite pretty and bloom as my azaleias are ending and before most of my early summer perenials. A web site mentioned that they are know for attracting wild life. I assume that they mean bees and butterflies, and perhaps humming birds. I think I will collect a few from an aquaintance's lot.
I'll let you know how it works out. Thanks for the info.
Jim D

I'd thought that dame's rocket was an invasive, but I may be mis-remembering...

Rh

be very careful with dames rocket..just spent most of a week transplanting dames rocket and garden phlox from what used to be a beautiful garden..they had crowded out almost everything but the daylilies! we moved them to our back fence..figure our hell-hound dogs will keep them in check..any dames rocket or phlox that can survive being run over or dug up can stay..the others can think about what they did to my Irises, balloonflowers and poppies before they go to plant heaven!

I will try them. I intend to contain them by planting them in containers and deadheading them. I will definatly keep my eyes on them. I am a robo weeder.
JD

I, too, live in SE Chester County.
I planted Creeping Phlox 2 years ago, unaware of how fast it spreads.

You can simply shear it off midway down and it'll bloom again.
If it spreads too much, I just pull some out.

I enjoy Dame's Rocket and have created large patches of it through harvesting and intentional spreading of seed. They are a prolific reseeder and can be invasive so don't plant near any native prairie plots and be careful with it in your flower gardens. Specimen plantings can be quite easy to control, though. Let the plants bloom and when they are finished simply cut off the entire stalk of green immature seed pods before they ripen and shatter - the stalk is unsightly anyway. If you forget to do this you could have tens or even hundreds of new plants.

BTW I have had good luck moving Phlox divaricata Woodland Phlox. It is fairly common around here but I wouldn't recommend transplanting if they are rare or uncommon where you live. Please don't dig them or anything else up from public lands either. Better to appreciate them in the wild.