I've had some of the legume weeds that RoundUp won't touch. Believe me, RoundUp is not quite as apocalyptically toxic as people think - there are some plants that naturally shrug it of without becoming resistant. I've got some Metsulfuron Methyl from Amazon under the name "MSM Turf" after looking for it under the wholesale names "Manor" and "Spotlight." 2,4-D would get the job done, but I have warm weather grass that is also sensitive to 2,4-D.
Common lespedeza, also known as Japanese clover, (Kummerowia striata syn. Lespedeza striata) is a very common summer weed that can easily choke out thin turf. It is often found in open woods and fields and frequently in disturbed areas and turf.
Lespedeza is a mat-forming, wiry stemmed, prostrate, freely branched summer annual. It has dark green trifoliate (arranged in threes) leaves with three oblong, smooth leaflets. Leaflets have parallel veins nearly at right angles to a prominent mid-vein. Its leaves have smooth edges and a short spur at the tip of each leaflet. Lespedeza has a semi-woody taproot and grows close to the ground, making it difficult to cut with a mower. It flowers in late summer with pink to purple, single flowers found in leaf axils on most of the nodes of the main stems.
But hey thanks for the diary and the chance to point out the RoundUp just isn't toxic enough to kill some fairly ordinary weeds.