It's been growing for several years now, and is about six feet tall. (My oval leaf Cassia, Cassia bicapsularis, that I planted at the same time is well over ten feet tall now.)

I think this plant is Privet Cassia, Senna ligustrina. There are so many kinds of Cassia that it's hard to tell. Regardless, my sulphur butterflies lay eggs on it, so I like it.

The seeds form in long sprawling pods.