Thursday, March 21, 2019

Pecan trees still dormant

     The calendar says its Spring and my peach trees are starting to show some pink buds. But it seems like its still winter in my pecan orchard.
    The first sign that pecan buds are beginning to expand is a bud stage that is termed outer scale split. I took the photo at right back in 2013 to illustrate what exactly outer scale split looks like. Note that the outer covering (or scale) that surrounds a dormant bud splits open when the bud inside starts to expand. Eventually the outer scale is pushed off the end of the bud to reveal a tight green bud underneath.
    I watch for outer scale split every year because this event coincides with the start of active tree root growth. Fertilizer is most efficiently taken up by actively growing tree roots so I make my Spring fertilizer application when I see outer scale split (I haven't fertilized yet).

   I checked three pecan cultivars for signs of bud growth; Faith, Hark, and Kanza. The photos above shown three twigs with fully dormant buds. From past experience, Faith will begin bud growth several days before Hark and Kanza. But as of today, Faith buds showed no signs of expansion.  Over the past few days we've experienced some mild daytime temperatures but our nights have still been chilly. It will take some warmer night time temperatures to wake up pecan trees from winter dormancy.     

Monday, March 18, 2019

Removing lower limbs

     One of the most common pruning mistakes pecan growers make involves removing lower limbs. It seems like folks get in a hurry to trim off all lower limbs with the idea they can force the tree to grow taller and faster. But pruning too severely can actually slow overall tree growth, enhance the development of stalked buds (which create narrow branch crotches) and cause sun scald damage to the trunk.
    While enjoying the sunshine and warm temperatures this past weekend, I spent some time pruning some of my pecan trees. The photo at right shows one of my Kanza trees. The tree has good form and requires no major corrective pruning. However, some of the lower limbs are just too low, making mowing around the tree with a tractor difficult. But when I prune lower limbs I take a "go-slow" approach. Lets take a closer look.
    The photo at left shows the lower portion of my Kanza tree's trunk. Four nicely attached limbs radiate from the central leader but they are all only 5 to 6 feet above ground level. All of these limbs will need be removed in time but not all this year.
    Last year I removed a single limb from this tree and the resulting wound has almost completely healed over (note wound just above the white marking paint). This year I'll prune another low limb.  Making the decision as to which limb to remove was not that difficult. I choose to remove the limb pointing to the left because it had another limb just above that would help fill its place in the tree's canopy.
    When removing a low limb I use my chainsaw to undercut the limb just outside the branch collar (photo at right).  Making this cut first will prevent possible bark tearing as I prune the limb off the tree.
     Next I use a plunge cut to remove the limb without damaging the trunk. I start the cut from the side of the branch leading with the lower half of the saw blade's tip (photo at left). Once the saw starts to feed into the branch, I complete the cut by pushing the blade through the branch and them downward. In making the plunge cut, I always try to align the blade at the same angle as the original undercut. This way I create a nice smooth wound.
   
     Once the cut is completed (photo at right), I don't treat the wound with any kind of tree would dressing. A healthy tree will heal over a wound of this size in just a couple of years. Just look how last year's wound has nearly closed over since last March.

     The above photos were taken before and after pruning. Note that the canopy of this Kanza tree has hardly changed. That's exactly why I take the "go slow" approach. By keeping the canopy of this tree largely intact I preserved both leaf area and nut bearing potential. After all, its the nuts I'm after. As this tree continues to grow in size, I'll keep removing low limbs at the rate of one per year until I achieve at least 8 feet of clear trunk. 
    

Monday, March 11, 2019

Still cutting pecan scionwood

    The month of March sure came in like a lion. On the morning of March 4th, we recorded the coldest temperature for the 2018-2019 winter; 7 degrees F (-14 C). So when things warmed up a little this past weekend, I went out to the pecan grove to check on twig health. Since my trees have remained fully dormant all winter the cambium under the bark was still bright green (photo above). Since the trees are still dormant and the wood is still in good shape, I took advantage of some better weather to cut even more scions.
     I had already cut all the scions I could reach from the ground while pruning my young trees, but this past weekend I needed to get up high into some more mature trees to collect wood from some of the trees in my pecan breeding block. Collecting wood from mature trees is usually a challenge because shoot growth is usually short and buds are close together (close buds make carving a scion more difficult).

     Up in the tree, I spotted what looked like nice long shoots--perfect for scionwood (photo at left). This tree happens to be a cross between Major and Pawnee. Note that even in early March the shoot is still hanging on to a few rachii from last summer's leaves. This is a characteristic inherited from its Pawnee parent.
    On closer inspection, I noted that these long shoots were actually a combination of both 2-year-old and 1-year-old growth (photo at right). Note that only the 1-year-old portion of the stem has large prominent buds. In contrast, all of the primary buds on the 2-year-old wood have aborted from the stem.
      Because of healthy large buds, I usually collect only 1-year-old wood for scions but in this case, the short shoot growth found on this heavily bearing and mature pecan tree is just not well suited for grafting.

     To gain a scion I can easily graft, I cut a scion that is part 1-year-old wood and part 2-year-old wood. I start by cutting the shoot off the tree at a point about 3.5 inches below the beginning of the 1-year-old wood. (photo at left). The presence of healthy buds on the lower portion of the scion is not important to graft success. This is the part of the scionwood stick that will receive all my cuts during the grafting process. For me, its important to harvest a scion that is at least 3/8 inch in diameter and contain more wood than pith inside the stick.  I've found that thin, pithy scions have a high failure rate.
    To complete this scion, I remove the upper portion of the 1-year-old wood. Note that I'll still have some nice plump buds to provide growing points for the graft.  In the end, I only harvested a single scion from each shoot. The scions are about 7 inches long in total and are exactly one half 2-year-old wood and one half 1-year-old wood.
    Although I much prefer collecting scions from young vigorously growing trees, some times you have to just make things work.  

Wednesday, February 27, 2019

Cutting pecan scionwood

     Folks often ask me when is the best time for cutting pecan scionwood. Yesterday, while cutting my own scions, the answer presented itself. A large flock of honking geese flew overhead on their way back north. It jogged my memory of previous years of scionwood collection and I realized that the spring migration of geese always coincides with the perfect time to cut scionwood.

   Earlier this week, we had some good weather for working outside and I cut scions for all the grafting I have planned for 2019. I started by attacking a young grafted tree that had grown a lot of strong vigorous shoots the previous season (photo at right). Most one-year-old shoots on this tree were 2 to 3 feet long.
     Looking at the top of the tree, I noticed that three shoots were competing to be the primary central leader (photo at left). In harvesting scions from this tree, I could not only get some great scions but I could train the tree back to a central leader.
    I cut almost every one-year-old shoot off this tree which yielded a good collection of twigs that could be cut into scions (photo at right). At this point in this young tree's life, I'm not concerned about cutting off all potential nut producing shoots. This tree is so small that any nut production at this stage would be minimal.

    I like to store my scionwood cut into pieces appropriate for making a single 3-flap or bark graft. When cutting the wood, I always make sure to pay attention to the location of buds near the top of the stick. I cut the wood about 1/2 inch above the upper-most bud, then make sure I have a second bud within the upper half of the stick (photo at left). I don't worry about buds on the lower half of the stick because they will be removed during the grafting process.

    While cutting up scions, I also look for stalked buds (photo at right). These type of buds do not prevent a graft from taking but they are a problem during scion storage. Stalked buds tend to puncture plastic storage bags increasing the risk of scion desiccation during refrigerated storage.
     You should note a strong secondary bud just below each stalked bud. I carefully snip off the stalked bud making sure not to injure the secondary bud (photo at left). Only after this detailed pruning is complete do I place the scion in a storage bag.

   
    A single long shoot can produce several scionwood pieces. The photo at right shows a typical one-year-old shoot harvested from a young tree.

    When cut into graft sized pieces, I was able to get six scions (photo at left). These sticks are arranged in the older they were cut from the shoot pictured above. The larger diameter scions are perfect for 3-flap grafts while the small diameter wood is better sized for bark grafting. I discarded the terminal piece.

 
 The photo above shows how I harvested the scionwood from a young tree. Note that I left a single shoot at the top of the tree to become a central leader. All other shoots were stubbed back. Next spring, this tree will sprout new shoots from two-year-old wood and fill out its canopy.

    I don't always butcher my trees to collect scionwood. Many times, I'll collect wood from the pruning cuts I make at this time of year. The tree pictured at right is a prime example. This tree has formed two central leaders connected by a narrow fork in the trunk. I should have spotted this problem a couple of years ago but I'll take this opportunity to correct the problem now and collect some scions.



     Just one cut with the chainsaw and I recreated a central leader tree (photo above). Yes, I see the branch fork at the very top of the tree. I didn't have my pole pruner on hand, so that cut will have to wait.

   Once I had the pruned-off portion of the tree on the ground, I  noted the numerous shoots that could be harvested for scions (photo at left). Again, young trees seem to produce nice long on-year-old shoots.

    With just one pruning cut, I was able to harvest a whole pile of scions (photo at right). Since the harvested scions range in diameter, I'll be able to find the perfect sized piece when it comes to matching scion to stock at grafting time. 
    I discussed proper scion storage in my previous post HERE.