budbreak. Today, all the catkins are out and you can still easily distinguish protandrous from protogynous cultivars even before pollen shed.
In the photo at right, you can see a branch cut from an Osage tree (bottom) in comparison with a Kanza branch (top). Osage is a protandrous cultivar and has short fat catkins while Kanza is protogynous as has long narrow catkins. Even though cultivars can vary in the number and size of catkins produced, the obvious difference in catkin shape between protandrous and protogynous cultivars seems to be universal.
Remember, pecan trees have one of two flowering habits. Those trees that shed
pollen before their pistillate flowers become receptive to pollen are
said to have protandrous flowering (also known as type 1
flowering). Pecan trees that shed their pollen late in the pollination
season and produce receptive pistillate flowers before they shed pollen
are called protogynous ( also known as type 2 flowering).
Having catkins and pistillate flowers mature at different times on a
tree is nature's way to ensure cross pollination.