This fast growing, strong rooted clover showed up in my yard this year. It grew in both a shady moist area and in a very sunny dry area. Due to the long, slender nature of its stems, it flops over onto the ground, which is why I didn't notice it at first. It looked like small clover from a distance. It is actually a few feet tall when not laying on the ground.

I have not seen it flower yet (it is September 26, so I cannot identify if it's helping insects, etc). While the plant and leaf color is attractive, it is quickly taking over the undisturbed areas where it volunteered itself. I tried digging one out, and the roots are very, very long, tough and hard to get out. 

The photos on this webpage show the flowering White Sweetclovers are pretty. Careful - it is aggressive in growth.