A little dormant pruning

   I've got a lot of young trees on my farm and not every one of them has grown according to the strong central-leader plan. Take this tree for example (photo at right). This Kanza tree looks vase-shaped with several side shoots competing with the central leader for sunlight. I guess I should have made a few more trips to the pecan orchard last summer to direct the tree's growth with summer pruning.
    At this time of year, I'll make just a few corrective pruning cuts help shape this tree. I don't like to cut off too much at this time of year because dormant pruning often forces the tree to regrow in unexpected ways.

   As I approached the tree, I got a good look at this young tree's branch structure (photo at left).  Notice that most limbs have formed nice wide-angled attachments. However, look at the lowest limb on the tree pointed out in the photo by the orange arrow. This limb is almost the same diameter as the central leader and is growing upward in such a way as to directly complete with the main trunk for supremacy. This limb is a great example of how forked trees can develop over time if a pecan tree is left to grow unattended.
    Its easiest to spot tree structural problems during the dormant season when limbs are not hidden among the leaves.  So once I spotted this low limb growing straight upwards, I got out my pruning saw.

     Before I cut off the limb, I took out my sharpie pen and drew a line indicating the proper position for removing this limb (photo at right). By making an angled cut as shown, I'll leave the smallest possible wound on the tree and a wound that will heal over quickly. Since the tree was still dormant, I was able to cut some nice Kanza scionwood from the pruned-off branch.

   Next, I turned my attention to some upright growing limbs a little higher up into the tree's canopy (photo at left). The arrows in the photo point to two strongly upright growing limbs that had developed on the side of the tree opposite from the limb I had already removed (see above). In this case, I am not going to remove these limbs entirely. I am, however, going to head these limbs back to outward growing side shoots.

    I simply cut off the upright growing portion of these two shoots and left all outward growing shoots in place. Look carefully at the photo at left and you can see two fresh pruning cuts.
    After these cuts were made the upper portion of the central leader became fully exposed to sunlight. The additional sunlight should stimulate the development of lateral branches further up the trunk and encourage the leader to continue growing straight up.
   I'll be back to this tree once spring's new growth has begun and I can make additional pruning cuts to direct the growth.

Early spring pruning on last year's bark graft

    I made a quick trip into my pecan orchard this morning to look at last summer's grafts. I stopped by the tree pictured at right to check the health of the scion and to trim the graft union. I grafted a Kanza scion onto this 1.5 inch diameter tree last May. After pruning the scion to one shoot in early July, this graft put on five feet of new growth during the summer of 2013. I removed the deer cage and quickly checked the scion's bark for signs of winter injury.  Even though this new graft had grown vigorously well into the Fall and this type of late growth can be prone to winter injury, my Kanza stem had green and healthy looking tissues inside the bark.

    I next turned my attention to the graft union. Last summer, I had cut off the green plastic tape that held the plastic bag around the scion allowing it to grow in diameter without being restricted. I left the remaining grafting wraps in place (photo at left). As is often the case, it looks like a bird had ripped open the plastic at the top of the stock, split the aluminum foil apart, and feasted on the ants that take up residence under the foil wrapper. I guess I should have taken my own advice and painted the graft union with white paint last summer.

    Once I removed all the graft wrappings, I could see how the tree was attempting to grow over the large wound I made by cutting the stock and inserting the scion (photo at right). The scion had grown to roughly 1/3 the diameter of the stock. Callus tissue had formed around the scion and had begun to cover the cut surface of the stock. Between the bark and the wood of the stock, I could see that a roll of callus tissue had developed part way around the circumference of the tree. This roll of callus is thickest near the scion then seems to dive down under the bark farther away from the scion.

    On the opposite side of the tree from the scion, the bark of the stock dies downward. To encourage rapid wound healing, I like to trim out the dead corner of the stock. I make the cut at about a 30 degree angle which seems to follow the natural way the tree is already forming callus tissue (photo at left).

      After trimming the stock,  I'm ready to replace the deer cage and move to the next tree (photo at right). Note that I still have the graft tied to a bamboo stake to prevent wind damage. The bamboo is attached to the stock with electrical tape and I used flagging tape to attach the scion to the stake. I'll keep the stake in place until the graft union is completely healed over. Once growth starts in the spring, I'll come back to this tree to make some "directive" pruning cuts to ensure I maintain a strong central leader.

Evaluating nut samples from the breeding project

    Growers that attended the Kansas Nut Growers Association meeting last weekend had the opportunity to look at all the nut samples we collected from our pecan breeding plot (photo at right). We asked each each grower to pick out their top 5 and jot the tree number down on a file card.
   Out of 216 total samples, 46 different nuts were rated as "top five".  Some of the more popular selections are shown in the photographs below. It is interesting to note that some growers seem to be most interested in large nut size while others look for the brightest, plumpest nut meats. You can count me as a member of the bright, plumb kernel team--I like the looks of KT149 and KT329. However, we will need to look at all of our trees for several more years before we can make an educated guess as to which seedlings might make outstanding new cultivars worthy of advanced testing.

Cold injury on Pawnee: Temperature and fruiting stress

Pawnee

   Pawnee is a large, early-ripening pecan cultivar grown by many northern pecan producers (photo at right). In previous years we have noted cold injury on Pawnee when winter temperatures drop below -10 F. So I thought it would be interesting to see how Pawnee fared following a colder than normal winter in the Mid-West. Recently, I asked some friends to provide me with some Pawnee shoots cut from their orchards growing near Columbia, MO. The lowest temperature they recorded at their location was -12 F. For comparison, I cut some shoots from our trees growing near Chetopa, KS where we recorded a winter low of -3 F.  
    In looking for cold injury, I selected both shoots that produced pecans last fall (i.e. fruiting shoots) and shoots that produced only leaves in 2013 (i.e. vegetative shoots). Using my knife, I peeled back an area of bark on each shoot to check for internal browning in the bark and cambium (indications of cold injury).

   The photo at left shows a vegetative shoot I cut from a Pawnee tree growing at the Pecan Field (KS). Inside the oval is a close-up of the tissues inside this twig. Note that everything inside the bark looks green and healthy. No cold damage here. A temperature of -3 F was not cold enough to cause injury to this Pawnee stem.

    Now let's look at a fruiting shoot cut from the same tree (photo at right). Again, a close-up of internal bark tissues is shown inside the oval. Note the internal browning of both the bark and the cambium. In this case, the stress of producing pecans caused this shoot to suffer cold injury at -3 F.

    In Columbia MO the winter low was -12 F. In the photo at right, I've placed two Pawnee shoots collected from an orchard just outside of Columbia. A vegetative shoot is on the left and a fruiting shoot on the right. A close-up of the internal bark for these two shoots is shown within the oval (in same left to right order).
    At -12 F both Pawnee shoots showed signs of internal browning. The vegetative shoot had only very slight discoloration while the browning observed within the fruiting shoot was intense.
    From this year's observations and observations we've made following previous winters, it also looks like Pawnee usually develops cold injury problems when temperatures drop below -10 F. In addition, it is clear that the stress of nut production can reduce the cold hardiness of Pawnee shoots helping to intensify alternate bearing .