Wednesday, June 20, 2012

Early maturing cultivars start kernel expansion quickly

    During the growing season, I like to cut open pecans to check on their development. This morning I was out in a pecan cultivar block cutting nuts and noticed that the earliest ripening cultivars had already pulled ahead of later ripening cultivars in terms of kernel development. Below is a photo of two nuts I cut this morning.

    At this time of year, pecan kernels appear as a small, water-filled sacks imbedded inside the nut. Like the photo in my previous post, the kernel starts out in the shape of a tear drop. However this week, the kernels have grown larger and started to change shape. From the tear drop shape, the kernel grows into a more blocky shape like the kernel of the Oswego nut pictured above. With continued kernel development, the water-filled sack takes on a heart shape as two kernel halves start to develop (Osage nut above).
     This fall, Osage will ripens 3 weeks before Oswego. But even today,  you can see an obvious difference in nut development phenology between these two pecan cultivars. Osage has already advanced further than Oswego in terms of kernel expansion. All pecan cultivars seem to become fertilized at about the same time (see fertilized vs. pollenized post), but the early ripening cultivars seem to develop far more rapidly than cultivars that end up maturing later in the fall.