Weeds are by definition,
a plant out of place. Some are fairly easy to control,
just pull them up and they are gone for the year.
Others, however, art tougher than nails and, once they
show up in your landscape, they are there for a long,
long stay.
The crazy thing is that
we often bring these thugs into our landscapes
ourselves. They masquerade as "ornamental" plants the
might add to the beauty of your landscape. Buyer beware.