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| Gardner pistillate flowers |
The weather in SE Kansas this spring has been cool, cloudy, and wet with only a few days of sunshine and warm temperatures. As a result, pecan bud break and flowering has been very uneven. This year my pecan trees responded to the brief periods of warm temperatures (especially warm over-night temps) with spurts of rapid grow. However, when the cool, wet weather returned, spring growth slowed to a crawl. The results has been an extended pollination season characterized by uneven pollen release and widely variable pistillate flower development.
It looks like we are about half way through the pollination season. The pistillate flowers of protogynous cultivars, like Kanza, appear to be pollinated (photo at left). The tips of the female's stigmas turn black in color after they have received pollen.
Protandrous cultivars have either shed all their pollen and dropped their catkins or are releasing pollen grains now. The photo at right shows the catkins of Yates 68. The center cluster of catkins has released its pollen and is starting to turn brown. The catkin clusters to the right and left are yellow in color indicating that the pollen sacs are fully mature and ready to burst open.
In the past, I've noted that pecan flowering type can be determined by the
size and shape of the catkins.
But in addition, protandrous and protogynous cultivars differ in the
appearance of their pistillate flowers. The pistillate flowers of
protogynous cultivars appear early and are often small in size. In
contrast, the pistillate flowers of protandrous cultivars develop later
and have much larger stigmas.
KT149 is protandrous and has showy red stigmas much like its Pawnee parent (photo at left). Kanza is protogynous and produces pistillate flowers that are smaller with yellow-green stigmas. The color of pecan stigmas can range from green to yellow to orange to red and is not related to flowering type. However, the size of the stigmas found on protandrous cultivars always seems much larger in comparison to the stigmas found on protogynous cultivars.
Most growers look forward to pollination season because they get their first glimpse into next fall's nut crop. Remember, the number of catkins produced by a tree is not related to nut load. Look for pistillate flower clusters as they emerge from the tips of this Spring's new growth (circled in photo at right). A full nut crop is produced when 50-70% of all new shoots are terminated by a pistillate flower cluster.
