Could it be a Chamaecrista ?

http://www.missouriplants.com/Yellowalt/Chamaecrista_nictitans_page.html

https://www.google.com/search?client=firefox-b-1-d&biw=1280&bih=625&tbm=isch&sa=1&ei=G3ndXK-eKoiYsAW4vqnoBA&q=Chamaecrista++seed+pods&oq=Chamaecrista++seed+pods&gs_l=img.3...46062.48626..48833...0.0..0.95.961.11......1....1..gws-wiz-img.......0j0i67j0i30j0i8i30.hgcmuG7DeOM

No, because the seed pods are different, and the leaves aren't sensitive to the touch.

Maybe a yellow dwarf poinciana?

Nope, I have one of those. Seeds are way different.

I'll wait until it gets larger and the seed pod fills out. That will probably help identify it.

Looks like a Sesbania but don't know which species. Some become small trees, others stay shrubby.

That looks similar to something that popped up randomly in my garden. I havent pulled it up yet because I was curious to see what it was. I will try to get a photo tomorow. My luck, its some hideous weed!

A sesbania species or a rattle bush? In Texas we have S. drummundi.

wantonamara, I think you have it. I found a Sesbania herbacea that looks a lot like it, although it seems to grow very large and change a lot as it grows. I'm going to let it grow just to see what it turns out to be.

Our prettiest sesbania is probably the Scarlet Wisteria, S. punicea. It's an invasive, but I've been trying to grow it anyway. I had one started, but it got root rot. I just pick the seeds off before they split open, so it doesn't spread.

Is the rattlebush anything I want growing in the yard? Do butterflies like them?

Sultry, bees love them. Not sure about butterflies. I had a few seeds left over, but can't find them now. They grow wild up here, so people say, but I've yet to find one. If anyone has seeds, I'd love to have some more, but only the orange/red one, not the yellow.

Speaking of yellow, do you have yellow dwarf poinciana? Mine should bloom this year, and they're cold hardy. I probably have a couple of seeds leftover I could send you.

Just be aware that they do seed out a bunch and can spread.

I think I'm going to toss it. The flowers aren't that pretty, and it doesn't have any other redeeming characteristics.

Wise decision. The one here is not that attractive either. It is a good stream bank stabilizer. Very useful in riparian restoration after a flood.

I have these around a small pond and they have been there for years. They are called Spanish Gold here. Also, I have never seen them anywhere else on this property

I have never seen butterflies on rattlebox.... but there is a little pink month that likes it as a host plant. Not sure what it is.... but when my daughter was in kindergarten some 20 years ago I had a butterfly month garden for her here at my house. Nobody could identify the month but is was pink.

It's gotten larger and I finally got to see a bloom open, and the seed pod get larger. Except for the seed pod, it's looking more like a partridge pea. I'm loathe to tear it out until I can see exactly what it turns out to be, but I'll take seeds pods off so it doesn't spread.

I think I found it. Sesbania sesban. It evidently changes a lot as it grows, having large drupes of flowers. I'm going to keep it, I think.

You will like it. They never get large here and these are growing two feet from the water.

Is it a type of cassia... I have several cassia plants... some trees others bushes... The way it has a nice green branch with the other two that seem to be dying back reminds me both of the popcorn or the peanut butter cassia... plus it looks like you have a yellow flower on it... neither of those cassia's are sensitive to the touch.