Try a mattock or pick axe to dig up the roots and stumps. That's what
my husband uses. If you leave the stems and roots, the plants will
probably sprout again or spread underground to another area where
they'll sprout. We've cleared a large area in our back yard that was
full of vines, weeds, brush, etc. As we clear another spot, my husband
digs up the stumps and roots and then we put topsoil and sod down.