No. Preen has no effect on any plant that is already growing. It only obstructs root development of newly germinated seeds.

I have to disagree on this one... sort of. Bigger plants will probably not suffer much, but I have had the experience of Preen's presence actually stunning the growth of small/young plants near the Preen's area, so there must be some lateral spread of the anti-growth stuff in Preen. I also have a friend that couldn't understand why her Sweetpea transplants were all dying. Turns out the neighbor on the otherside of the fence had Preened his whole fenceline.

What about planting next to the path after Preen is applied in the pathway? Thanks for the good information but I'm really interested in far a reach Preen's effect is? Of course I'm not going to plant in the path itself *lol* but can I plant next to the path after Preen is applied? I was thinking for next year putting down Preen early in the season to hopefully cut down on weeds asap and then planting some plants that want to warm up a bit more before their planted.

Once again, IMHO, it depends on the age of the roots.... baby plants with a young root system might have a problem anytime after the Preen is applied.