Back in 2012, I photographed some terminal branches that had already started vegetative shoot elongation. By that time, the differences between cultivars that shed pollen early (type 1) and those that shed late (type 2) were very obvious. The photo I took today shows pecan growth at a much earlier stage of development (photo above, right). Here the differences between protandrous and protogynous cultivars are a little more subtle.Let take a closer look.
The shoot on the right was cut from a Major pecan tree. Once the outer scale splits opens and falls off you will see what looks like 3 buds inside (see red arrow). The bud in the center will develop into a new vegetative shoot that will eventually terminate in a cluster of female flowers. The green buds that flank the central bud will develop into catkins. Note how plump and large the catkin producing buds are on the Major twig as compared to the thin, less-noticeable, catkin-containing buds that surround the vegetative bud on Kanza. To produce pollen early in the flowering season, Major catkins need to start developing early, starting right at bud break. In fact, the yellow arrow points to Major catkins starting to emerge from under the inner bud scale.
In comparison, late-pollen-shedding Kanza will expend most of its early growth energy creating new shoots capable of producing mature pistillate flowers quickly and ready to receive early flying pollen. Catkins will develop on Kanza at a much slower pace and will not begin to shed pollen until after pistillate flowers have pollinated by a protandrous cultivar like Major.