Monday, May 17, 2021

Pecan pollination underway

Kanza catkins and new growth
    During mid-May I scout my pecan orchard for the intensity of pistillate flower production on new branch terminals. If I find a flower cluster on nearly every shoot, I expect a good nut harvest come this fall.

   The amount of catkins produced by a tree has no bearing of the nut crop produced in the Fall. Although large amounts of wind-blown pollen is necessary to fertilize a large pistillate flower crop, there never seems to be a shortage of fine yellow pollen grains floating in the breeze during the month of May (in our area).

Kanza pistillate flowers
     Pecan pistillate flowers (female) are found on the very terminal end on the current seasons new growth. Each flower in the cluster has a prominent stigmatal surface that is designed to capture pollen grains out of the air. Each stigma has two horns and features a very rough surface. The stigmas of Kanza flowers are green. However,  stigma color among pecan cultivars can varyfrom green, to orange, to red. Since insects are not required for pecan pollination, stigma color has no impact of pollination success. 



Pecan trees have one of two flowering habits. Trees that release pollen before their female flowers become receptive, have a protandrous flowering habit. Trees that produce female flowers that are receptive to pollen before they release their own pollen are termed protogynous.  Today, I found several protandrous cultivars had started releasing their pollen. You can tell pollen is being released because the pollen sacs on the catkins have split open and are turning brown. Gardner pecan, as seen in the photo above, was  releasing pollen today.  

    Pecan trees have developed this dichogamous system of  flowering to prevent self pollination and inbreeding depression.

    If you would like to discover the flowering type of your pecan trees, simply collect some catkins from each cultivar. The first thing you will notice is that catkins are produced in clusters of three. Even before pollen release you can identify flowering type by the shape of the catkins produced. Catkins of protandrous cultivars are short and fat while the catkins of protogynous cultivars are long and narrow (photo at left).