In the photo above, look carefully at the shape, size, and texture of the catkins produced by the Kanza and Osage cultivars. At this time during the season, the catkins on the protandrous Osage shoot have already grown plump with the individual pollen sacs clearly visiable. It won't be long until these catkins will begin to shed pollen. In contrast, the catkins on the protogynous Kanza shoot are narrow, not yet fully extended, and the pollen sacs still tightly bound along the catkin's stem. These catkins will release their pollen much later.
As the season progresses, the differences in catkin size and shape become even more striking. Check out the photos from last spring.