I live on a street that borders the RiverLine tracks. Between the street and the tracks is a ditch that is about 4-6 feet across and maybe 1-2 feet below grade. Usually this fills up with grass and weeds (and litter). The ditch is well watered with runoff from the track ballast, so weed growth is very thick and lush.
My first thought was to put sunflowers there, but this area does occasionally get mowed. I think wildflowers would be a great idea, since they would generally recover from mowing and would self-seed. One good, heavy application of wildflower mix should be enough to fill this ditch with flowers for years, and may even choke out the weeds.
I have a can of wildflower seed, but the area I'm talking about is probably a half-mile long. If anyone wants to get in on this, please leave a reply.
Our town is pretty good on flowers and gardens, but there are still areas we could improve.