Early this morning, I walked out to a couple of pecan trees to check on the progress of this year's pollination season. I stopped first at a Lakota tree (photo at right). Lakota has the protogynous flowering habit meaning that pistillate flowers become receptive to pollen early in the pollination season. Stigmas of Lakota flowers are green when receptive but turn brown once pollinated. In the photo above, note how the tips of these Lakota look dried up and have started turning brown. It seems that pollen has already landed and germinated on these flowers.
In contrast, the pistillate flowers of a Gardner tree appeared fully receptive to pollen today (photo at left). Gardner has the protandrous flowering habit meaning that the tree sheds its pollen before pistillate flowers become receptive. The stigmas of Gardner pistillate flowers are wine red in color but notice how they glisten in the sunlight. A pistillate flower secretes a sticky fluid that serves to help capture pollen grains from the air and subsequently promote their germination. Today's warm sunshine provided Gardner flowers great conditions for getting pollinated.
In looking over your trees, remember that the color of the stigma does not indicate receptivity for pollination. Pecan stigmas can vary in color from green to yellow to orange to deep red. Look for the presence of stigmatal fluid on the flower. A sticky stigmatal surface means the flower is fully ready for pollination. Once the flower is pollinated the stigmatal fluid will disappear and the tips of the stigma will begin to brown.
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