Might be Grain Amaranth. HTH Chris Here is a link that might be useful: see botton of this page

Ricinus communis I believe. Here is a link that might be useful: 'Carmencita' Ricinus Flower

Kelton, Has your lot been cleared recently (within the last few years)? The reason I ask is that redbuds will almost always resprout in that situation. You may have well established root systems sending up shoots. Also, even if the ones you are seeing are new seedlings (not regrowth), they have a much better root system than your transplants. Redbuds are notorious for being finicky to transplant. The ones you planted will only start growing at rates similar to permanent residents when their root system catches up with them. It usually takes a while for a redbud to decide it even wants to live when transplanted. Chris, Transplanting redbuds may be more difficult than many other trees, but it can be done. Most of the redbuds you see at nurseries are pot grown and root pruned. If you do decide to transplant yours and they make it after the trauma, give them a few years to get established and then chop them off at ground level just above the root collar in late winter/very early spring. Chances are about 97.643% (or at least real good) that they will resprout, and when they do, they'll send up a few nice straight trunks fairly quickly. Just remove all but one shortly after you see them, and keep an eye on the one you keep to make sure it develops a good branching habit, etc.

@macranthos, yes there are quite a few river birch in the neighborhood, some within a block. Thanks for pointing that out, I didn't know what kinds of trees those were before your comment. And it probably explains this other volunteer I have (picture below), which seems likely to be Betula nigra. Interestingly it has the same red stem as the smaller seedlings I originally asked about, which look a great deal like the photo you posted. And yes, I also have them all over the place in my back yard and deck container pots.