Mission for Duh
Birr was the home planet of the Verdant.
The First Doctor met the Verdant leader Phlege there. On his return visit, he discovered that a Rostrow space mission led by Lahk had arrived to gather plant specimens, unaware that they were taking intelligent beings prisoner. In return the Verdants were preventing the Rostrow ship from leaving. The Doctor, with the assistance of Duh, helped to make peace between the two peoples. (Mission for Duh)