Black Medick isn't the most highly desirable plant. A Google search shows about half of the sites refer to it as a weed and have recommendations on how to get rid of it. It's not native to North America and grows well in lawns and patios.
It looks like a clover but is closer related to Alfalfa, being in the same genus. It's actually rather difficult to differentiate between this and some of the Trifolium "Hop Clover's". I've seen all sorts of descriptions of the lengths of the leaflet petioles and tips at the ends of the leaflets, but the sure way to tell is to find the fruit, which is distinctive for Black Medick.
|Grows nicely within cement cracks|