Freeze injury to pecan buds

Kanza buds, 20 June 2018

    On Monday morning, April 16th, a strong cold front ushered in some very cold temperatures. We recorded 24 degrees F (-4 C) just after sun rise. Dormant pecan buds can easily handle 24 degrees but green pecan tissues freeze at around 26 degrees. Pecan bud development had not advanced much by April 16 but after the freeze many buds seemed to remain in a state of suspended animation (photo at above, right).

Kanza buds, 20 June 2018

     I decided to cut open some buds to see if I could spot cold injury (photo at right). Healthy buds should appear bright green. These buds darkened with dark brown streaks, sure sign of cold injury.

Kanza buds, 20 April 2018

     I cut open some more buds and found some were still green while others were black. It seems that this Spring's cold injury will vary widely both withing the canopy of a tree and between cultivars. One thing is certain, the 2018 pecan crop will be reduced.

    I looked at several cultivars and found shoots with damaged buds (no signs of further buds enlargement)  and shoots with nice green buds. The photo at left shows two shoots cut from the same Faith tree. The shoot on the left has emerging pecan buds that are plump and green. The shoot on the right has buds that look almost shriveled and have failed to "green-up" since the freeze. This kind of variation in damage seems very common among several pecan cultivars.
   

      I was encouraged to find that the two buds I cut open from Hark shoots looked healthy and not damaged (photo at right).
    We have suffered through late spring frosts in previous years with each episode causing different amounts of crop loss depending on the stage of bud development when the frost hit and the health of the trees. Back in 2014, we saw significant bud injury but the trees were able to produce pistillate flowers from buds lower down on the shoot. Come this May, I'll be evaluating pecan cultivars for their ability to produce female flowers following this freeze.
    Although I don't know the full impact this year's Spring freeze will have on nut production, I do know that the start of the Spring grafting season will be pushed back at least a week. I always like to see active green growth on my stock trees before I start grafting. 

Signs of Spring

    Our resident pair of Canada geese have returned from their winter habitat and are making enough noise to ensure we know Spring has arrived (photo at right). Canada geese mate for life and return year after year to the same nesting site. So far we've seen this pair raise at least six broods of goslings on our farm pond.

   Our pecan trees are still waiting for some warmer temperatures (especially warm night-time temperatures) before bursting out with a new crop of leaves. This year, pecan bud break is proceeding slower than normal. The buds have swollen but leaves have not yet emerged (photo at left). This slow bud development has been a blessing as we have experienced several hard freezes in early April and not suffered any cold injury.
    The pecan grafting season will start late this year. I like to see the first signs of leaf burst on stock trees before making any grafts. At this point, I probably won't carve a single scion until early May.   

Spring cleaning

   Sunshine and warmer temperatures made for a great day to be out in the pecan orchard today. It was also a good time for Spring cleaning. Our first task was to burn all the piles of sticks we had raked up during harvest last fall (photo at right). Its best to get this mess cleaned up before the grass grows up and we lose tract of large chucks of wood in the tall grass. Hitting a heavy piece of pecan wood is hard on our orchard mowing equipment.

   Over the last several weeks, we've had several wind storms that has littered the pecan grove with even more dropped branches. While we burned last fall's piles, we raked up even more sticks to add to the fire (photo at left). We use a Rouse hydraulic hay rake to rake up the sticks.

    We weren't the only one cleaning up pecan groves. Our neighbors to the south were raking their groves and piling the brush with Stidsteer and attached grapple (photo at right).  With all the brush piles burning, the entire river bottom was covered in a smoky haze. By morning, the smoke will be gone and our orchard will be tidy.

Pecans survive cold snap

    Over the weekend, a cold front swept across the plains and dropped our temperatures down to 22 degrees F (Saturday morning 7 April 2018). At that point in time, the buds on our pecan trees were just starting to swell and the outer scales of many apical buds had fallen off. The photo at right shows a typical pecan terminal.
    The terminal bud at the very top of the shoot has lost it outer bud scale. Likewise the upper bud on the right side of the shoot. The bud immediately to the left of the terminal bud is actually the secondary bud to the terminal bud and is still covered by its outer scale. Further down the shoot on the left side, a bud has split open the outer scale but its has yet to fall off.

    To check for cold injury, I removed the terminal bud for closer inspection (Photo at left). Once the outer scale falls from the tree, you can see that the bud is actually made up of three parts. In the center is a large vegetative bud that produces a new shoot that terminates in a pistillate flower cluster. On either side of the vegetative bud are two lateral buds that will produce only catkins.

     I sliced the bud in half to reveal the health of the bud (Photo at right). Again you can see the large vegetative bud in the middle flanked by the catkin-containing lateral buds. Fortunately all the tissues inside the bud a still green and healthy. A cold injured bud would have appeared black in color, two days after the deep freeze.
   I guess its a good thing pecan trees break bud late in the spring. The freeze on Saturday, did significant damage to my peach crop (trees were in full bloom).  Which is the main reason I have 20 acres of pecan trees and only 2 acres of peaches. Peaches are great when you have them but pecans are far more reliable.

Pecan cultivar information updated

Oswego Pecan 2017

    I just finished updating the pecan cultivars page of this website. I included new photos (example at right), additional cultivars, and additional nut data. So go check it out (press the Pecan Cultivars tab at the top of this page).