I dug up wild lupins on the side of the road and planted them in my yard. They have flowers on them. should I cut them down.
I would think anything to decrease the stress on the transplants would help. So, I would cut the flowers off and let the plants concentrate energies on new roots.
Lupins dislike transplanting especially this time of year. Better to do it in spring or fall. Or collect seeds and plant. Most "wild" lupins are garden escapes not native plants.
You do know it is illegal to dig up plants without permission from the landowner. That includes plants at the side of the road.
It is also very unethical where native plants are concerned. It contributes to population decline. If they dont' make it, that is a few less lupines around. If you want these plants, please buy them from a responsible grower (check them out, there are a fair share of wildflower "nurseries than dig wild and sell them, stay away) or collect the seeds and grow them. Remember that native plants are often hosts plants to many wildlife species so they should remain where they are.