While studying permaculture and regenerative agriculture I came across this thread on native species and it stuck with me. I’m now in the camp of, “the world is changing and what grew in an area before night not be the right thing to grow there now”.
Typically wildflowers in an area are synonymous with weeds. They shouldn’t have any trouble growing if you break the current grass monopoly even a little. Most people have a hard time getting them to NOT grow in their yard. I had good luck including Jerusalem artichokes (sunchokes) in my yard. They are HUGE when fully grown and you will basically need a flame thrower to get rid of them but the birds and bees love them. They also spread risomatically by sending out root runners, so they break up compacted soil. A combination of those and sunflowers would basically be a 2 meter tall flower bed. I don’t think you would even need the cardboard.
This is a great take on the subject. In my area the Jerusalem artichoke would mostly be competing with Asian honeysuckle and Bradford pear trees which have already escaped captivity and killed everything else, but I completely agree that releasing virulent species into any kind of intact ecosystem can be very damaging.