Tuesday, January 30, 2018

Selecting scionwood

    On long cold winter days, my thoughts turn towards collecting scionwood in preparation for next Spring's grafting season. The best scions are often found growing at the tops of young pecan trees (photo at right). However, I make it a practice to wait until a tree starts bearing nuts before cutting wood from a tree. This way, I verify that the tree is true to cultivar before cutting scions.

   Walking up to the tree pictured above,  I noticed that the lower branches had very short one-year-old wood and that twigs were small in diameter. Last year's wood was only three inches long (length of the blue arrow)--not nearly long enough for a proper scion stick (photo at left).
    The pedicel at the end of the shoot (red arrow) indicates that this shoot held a cluster of nuts last summer.  When a branch is located within the lower portion of the canopy, the combination of partial shade and nut production slows shoot growth dramatically. With limited sunlight, the shoot invests all available energy resources into nut development rather that shoot extension growth.
    Ultimately, short shoots make poor scions because the buds on the stem are too close together and the diameter of the stem is less than that of a pencil.

    High up in the canopy of the tree the shoots were longer. Normally I can find some pretty good scions at the top of a tree but in 2017 this Kanza tree had a full nut crop. Rather than growing a nice thick vegetative shoot, upper branches on this tree set a cluster of nuts (pedicel marked by purple arrow) and then produced a secondary flush of vegetative growth. The result were shoots long enough for scionwood but too small diameter to make really excellent propagation material (photo at left).
    To ensure a plentiful supply of scionwood, we have developed an orchard of trees specifically trained to produce long, thick vegetative shoots. I call it training but what we are really doing is chopping back the tree to keep the tree short (so we can reach the scionwood with our hydraulic lift) and force the growth of new vigorous vegetative shoots. In the photo at right, you can see numerous shoots growing from one of our scionwood trees.

    The photo at left shows a couple of one-year-old shoots that I cut out of the top of a scionwood tree. These shoots are between three and four feet in length. The buds are far apart and the wood is the perfect diameter for scionwood. When I cut scions, I'll break down these long shoots into sticks that contain at least three buds. I'll discard the terminal portion of the shoot, where buds are spaced too close together and the shoot is too thin. 

   One of the side effects of forcing vigorous vegetative growth on pecan trees is the development of stalked buds (photo at right). The red arrows point to stalked buds that look more like short stems than buds. Although stalked buds do not impact a scions ability to sprout and grow after grafting, I make it a practice to prune off these stalks before storing the scions in the cooler. Left on a scion, stalked buds have a tendency to puncture the plastic bags I use for scion storage. I surely don't want to risk having my scions dry out in storage because of a hole in the bag.
    If you plan to graft a large number of trees, it pays to plan ahead. Develop your own scionwood trees this March and harvest high quality scions the following year. Once you finish grafting your orchard, scionwood trees can be left to grow normally and eventually return to become productive nut trees. 

Friday, January 19, 2018

Greenriver vs. Oswego: Kernel quality problems

Greenriver kernels, 2017
    Last summer we thinned the nut crop on several pecan cultivars including; Pawnee, Lakota, Faith, Gardner, and Kanza. Later, when we harvested the nuts from these cultivars, we found good to excellent kernel quality inside. However, after cracking open this year's Greenriver nuts, it looks like we should have thinned the crop on this cultivar also.
    The photo at right illustrates the type of kernels I found inside our Greenriver nuts. About 25% had darkened kernels and another 25% had kernels that where somewhat hollow inside.
Oswego kernels, 2017
   Oswego originated as a seedling of Greenriver. The nuts produced by Oswego are very similar in size and appearance to its parent. However, when I cracked a sample of Oswego nuts I found the kernels to have better color and nut fill (photo at right).
   Why the difference? It boils down to crop load.  At the Experiment Station,  Greenriver and Oswego are located in the same block of trees, grafted to the same rootstock, with very similar trunk diameters. In 2017, our Greenrivers  were loaded with nuts. In contrast, Oswego trees had a good crop of nuts but the limbs weren't hanging on the ground like our Greenriver trees.
    Over-production reduces kernel quality. With Greenriver, over-production caused a darkening of the kernel and meats that were not solid. Over-production is a manifestation of Greenriver's strong tendency towards alternate bearing. Next year, our energy-drained Greenriver trees won't have the capacity to produce many pistillate flowers. The 2018 Greenriver crop will be tiny.  Summer shaking is the only tool we have for reducing alternate bearing and I wish we would have shook our Greenriver trees last summer.

Tuesday, January 16, 2018

Deep winter chill

    Winter has returned with a few inches of snow and bone chilling cold temperatures (photo above). So far this month, we have dropped to -3 degrees F (-19 C) and I've been wondering if we will see any cold damage displayed this coming Spring. Two types of pecan trees are most prone to winter injury: Vigorously growing grafts made last year and mature trees that produced too many nuts last Fall.
    For graft injury, it doesn't seem to matter which cultivar was grafted but rather, how late a graft grew into the Fall. Pecan shoots that don't harden off before a hard freeze seem to suffer the greatest amount of shoot dieback.
    Pecan cultivars that over-produce and have some southern blood are the most prone to suffering winter dieback. Shoshoni, Chickasaw, and Mohawk are cultivars we no longer grow because of over- production and subsequent cold injury. Last year, we made sure to summer shake our Pawnee and Lakota trees to prevent over-cropping and limit the possibility of winter injury.
    Thankfully, we have finished harvesting the 2017 crop and we are now cleaning the last few super sacks our pecans in a heated barn. 

Monday, January 8, 2018

Yields from a young pecan orchard

Harvesting a young orchard
   Frequent questions new pecan growers have usually revolve around questions of when and how much young pecan trees start to bear nut crops. Back in 2002 we planted one-year-old Colby pecan seedlings to start a new block of trees. Most of these trees were grafted in 2005, with every tree in the planting successfully grafted by 2007. We grafted three cultivars; Faith, Gardner and Lakota. The trees produced a handful of nuts by 2010 and as the trees grew larger nut production steadily increased.
   By harvest time 2017, the trees in this orchard averaged over 7 inches in diameter and were producing a full crop of nuts. Lets take a look at this year's yield data.

    This field of young trees contained 32 trees of each cultivar. We harvested each cultivar separately and then calculated yield per tree. In the chart at right, I list the average yield per tree and present a measure of the variation in yield observed between trees grafted to the same cultivar (mean yield +/- standard deviation).
 Twelve to fourteen pounds of pecans per tree doesn't sound like a lot of pecans but, when added up on a per acre basis, the income generated by these young trees is significant.
   The trees in this orchard were planted at a density of 27 trees per acre. This means that Gardner produced 327 lbs/acre, Faith produced 378 lbs/acre, and Lakota 359 lbs/acre. I sold these nuts for $3.00 per pound which translated to a gross return that ranged from $981 to $1134 per acre depending on cultivar. That's not bad for a 15-year-old pecan orchard.

Friday, January 5, 2018

Native pecan yield 2017

    Every year I learn something new about native pecans. This past summer (2017), the branches of our native trees were hanging low with, what I thought, was a heavy nut crop. However, this past year our native trees fooled me. The limbs were weighted down with a huge leaf crop that hid a below average nut crop.
    It was only when we began shaking trees, that we discovered the true nature of the 2017 native crop.

     For 37 years we have be recording the yields from 6, one-half-acre plots of native pecans. The 2017 yields are presented in the table above (numbers listed in Lbs.). The half-acre plots are labeled A thru F.  We always harvest each plot twice; the first time in mid November and then again in late December. The weight of nuts collected at each harvest time is listed above.
    The 37 yield average yield/acre for these plots is 1150 lbs. The 2017 crop averaged 798 lbs./acre or 30% below average. What was interesting about the 2017 harvest was that we harvested almost one third of the crop (32%) during the second harvest. Prior to 2017, second harvest yielded 15% to 20% of the total crop. Why the difference in 2017?
    I blame the heavy leaf crop. During the first harvest, our pecan harvester had a tough time digesting all those leaves. A lot of nuts ended up riding on a stream of leaves and getting blown out of the back of the machine. When we went back for the second harvest, the leaves had been chopped up and partially broken down by our first harvest operation. During the second pass over the field, the harvester could easily process the ground up leaves and orchard floor was swept clean of nuts.  
   A below-average nut crop and an above-average leaf crop in 2017 is a sure sign that the potential for the 2018 native crop will be huge.