A friend in Transformative Adventures was asking how to get rid of crabgrass that’s taken over a veggie bed. I replied:
When a patch of something tenacious grows, I put some old carpet or other thick material over it and wait for it to die and become a nice brown sponge of carbon-rich organic material. I then remove the carpet, and slash-plant my preferred plants into the brown sponge.
(Works for all other types of grass and other things you don’t want as well.)