Guessing Silphium owing to the broad phyllaries and opposite leaves. Here is a link that might be useful: Silphium radula This post was edited by saltcedar on Mon, Jun 3, 13 at 10:25

1. Japanese Knotweed. 2. Campanula divaricata? Here is a link that might be useful: Fallopia japonica This post was edited by saltcedar on Tue, Aug 20, 13 at 21:45

I don't think that is Lespedeza cuneate, because that species has leaves that are squared off a bit on the tips. Leaf tips on the first plant appear to be acute. The second one may be Agalinis fasciculata. It seems to be too leafy for A. purpurea.

I could be wrong, but your photo looks a lot like what my Dad always ID'd as Jerusalem Thorn. He actually planted a few on his property in Texarkana. They look a lot like your photo when very young but more like a weeping willow to me with age. https://images.search.yahoo.com/yhs/search?p=Jerusalem+Thorn+Tree&fr=yhs-mozilla-001&hspart=mozilla&hsimp=yhs-001&imgurl=http%3A%2F%2Fpictureplants.com%2Fsites%2Fdefault%2Ffiles%2Fplants1%2FPicture%2520Plants%2520Jerusalem%2520Thorn%2520tree.jpg%3F1330109798#id=26&iurl=http%3A%2F%2Ftoptropicals.com%2Fpics%2Fgarden%2Fm1%2FPodarki_13%2FParkinsonia_aculeata1005OlgaB.jpg&action=clickThe soft frond-like leaves flow beautifully in a breeze and in Spring, they have delicate yellow blooms. I used to see them all along the roadways in southeast Texas and they were all around Texas City when I lived there.