How about low growing wildflowers?

Seriously, you need to look at the soil, moisture and sun conditions of the ditch, then select plants that will do well in those conditions. Whether you choose wildflowers or a ground cover, if you use seeds, not plants, you will need to weed the area at least once a week for the next year or two or three until the desired plants are large enough and dense enough to compete with weeds.

Or you chould mulch with 4 to 6 inches of mulch to stop new weeds from germinating and use nursery grown plants or plugs instead of seeds.

Have you considered crown vetch? It grows just about anywhere and chokes out everything else. As Judy B ON said, the first year is critical and requires you to keep the competition at bay. You buy these as crowns and set them out in the fall or early spring. Pretty clover-like blooms and take the Pennsylvania winters and road salt without a care (developed right here at Penn State).
Later,
Chiz