Tuesday, October 25, 2011

Shuck split date and young pecan trees

    For northern pecan growers, the date of shuck split is one of the most important cultivar attributes we measure. Pecan cultivars that are well adapted for production in our area, split shucks at least one week before the average date of first fall freeze.  Late ripening cultivars usually suffer from poor kernel fill, fuzzy kernels, or "stick-tights" (pecans frozen in the shuck).
    In testing new cultivars, we are always anxious to discover the average date of shuck split. However, we have learned to be a little patient before coming to any conclusions about ripening time. In the photo above, you see two clusters of pecans. Both clusters were collected on the same day and from the same cultivar--Lakota. The cluster on the left was taken from a young tree (4 inches in diameter) while the one on the right was taken from a tree 28-years-old (12 inches DBH). In previous posts, I've talked about tree age and drought stress and how pecan trees grow to dominate the landscape. Here is another example of how young trees can differ from mature trees.
     Lakota pecans taken from the mature tree have been split for a good two weeks. Note the browning of the shuck near the tips and along the edges of each shuck quarter (pecan on right). In contrast, only one of the 5 nuts in the cluster cut from a young tree shows any signs of shuck split (pecan on left).
      Break off the shucks and you can see further evidence that pecans produced by young trees have delayed nut maturity. Full shell color has not yet developed (nut on left) as compared to the pecan collected from the mature tree (nut on right).
    It is no wonder why it takes so long to develop and test a new pecan cultivar.  Only trees that have grown large enough to "dominate the landscape" provide reliable nut size and maturity date information.