With a week of cool days and even cooler nights, pecan shoot growth has slowed to a crawl. However, when I looked at my trees a few days ago I could already see new leaves and catkins emerging from terminal branches. The photo at right shows the terminal of a 'Gardner' branch. The stem seems to be covered with emerging catkins with a single vegetative bud at the top of the shoot. This type of spring bud emergence is typical for a protandrous pecan cultivar such as 'Gardner'. The word, "protandrous", can be roughly translated as "first male" and describes a pecan cultivar that sheds pollen before the pistillate flowers on the same tree become receptive to pollination.
The photo at left shows the terminal of a 'Kanza' shoot. Vegetative growth on this shoot is far more advanced with catkins only now starting to emerge from their bud scales. 'Kanza' is a protogynous cultivar. The word "protogynous" can be loosely translated as "first female". Pecan pistillate flowers are produced on the ends of new shoots which means that protogynous cultivars prioritize shoot growth over catkin growth during the initial phases of bud development. Ultimately, this advanced vegetative growth will lead to the pistillate flower clusters becoming receptive during the earliest part of the pollination season.
In the grand scheme of things, a protandrous cultivar will pollinate a protogynous cultivar and vice versa. Since pecan trees are wind pollinated this dicogamy of flowering types ensures that nuts form as the result of cross pollination. Cross polination imparts hybrid vigor in the next generation of pecan trees (seedling trees grown from nuts) ensuring the continued survival of the species.