I planted lettuce early this year and it didn’t come up. I figured it was bad seed and forgot about it. Then the volunteer black oil suflowers popped up and I let them grow, not weeding under them.
The lettuce came up under the sunflowers as an understory and were very slow to bolt, I think it is because of the shade the sunflowers provided.

Sunflowers are great, they grow like weeds. They, amaranth, and squash were species in the Eastern Agricultural Complex that was the various cultivated crops in the Mississippi valley Indian cultures until mostly displaced by the adoption of maize. They have the benefit of being native and easy to grow, if you are considering an feed plot for pigs. We even call Amaranth “pigweed” here, though it has nicer names as well.