Gotta love Google!
I have not tried these.
OK, natural weed killers include:
Boiling water (applied directly to the weed. According to one site, this kills the weed but not the grass. A good option.)
Vinegar. This kill some weed better than others. I particularly am interested in broad leaf thingies. Clover, I don't consider a weed.
or the following recipe:
1 gallon of vinegar,
1 cup of salt
a squirt of dishwasher liquid (this helps it stay on the weed and not go everywhere or run off.)
Hmmmm...seems like the application of all of the above would be work, but then so would the application of some vile ortho poduct, roundup or some such.