Friday, May 19, 2017

Checking on pecan pollination

    Yesterday, I wandered through our pecan cultivar trials to check on the progress of pecan pollination.  At this point, we are half way through pollination. All of the protogynous cultivars are releasing pollen and the protandrous cultivars have receptive pistillate flowers. Pawnee is a protandrous cultivar that is now displaying large, red stigmas on the ends of pistillate flowers (photo above).  The catkins on Pawnee shed their pollen a while back and have now dropped to the ground.

     The pistillate flowers of Kanza are fully pollinated (photo at left). Stigmas of female flowers dry up and turn black once they become pollinated.
    Kanza, being a protogynous cultivar, has late pollen release. Yesterday, Kanza catkins were releasing millions of pollen grains into the warm springtime winds.

    One thing I noticed about pecan flowers is that pistillate flowers of protogynous cultivars are smaller than pistillate flowers of protandrous cultivars.  In the photo above, you can see this size difference. Posey is protogynous while Pawnee is protandrous. By the end of the growing season the nuts of these two cultivars will be roughly the same size.

    While inspecting pecan flowers, I was also reminded that the color of receptive stigmas can vary from green, to orange, to bright red. The photo above illustrates some of this color variation. Both Major and Waccamaw had fully receptive pistillate flowers yesterday. Major displayed green stigmas while the Waccamaw stigmas are bright red. Since pecan trees are wind pollinated, stigma color has zero impact on pollination success. However, stigma color can sometimes be used to help identify certain cultivars.