Evaluating new pecan cultivars: A look inside the shell

     2013 turned out to be a good year for evaluating new pecan cultivars. The above average rainfall we received this past summer meant that soil moisture would not be a limiting factor in terms of kernel fill. However, the 2013 growing season was significantly shorter and cooler than normal. Lets take a closer look at the kernels inside the shells of three cultivars to see how cooler temperatures can impact nut quality.

    Let's start by looking at an open-pollinated Giles seedling we originally planted in the Chetopa City Park.  On the outside, this nut is large and attractive. City Park is larger than its Giles parent but smaller than Mohawk (the possible male parent). At first glance the kernels look OK but on closer inspection I note a lack of plumpness and some shriveling towards the tip of each kernel half. I also spot some kernel fuzz on surface of the kernels.

    USDA 75-8-5 and USDA 75-8-9 are sibling cultivars that resulted from a cross of Osage and Creek. Both cultivars produced medium-sized pecans this year. The kernels are bright and attractive but upon closer inspection, both cultivars have a significant amount of fuzz on the surface of the nut meats. In a previous post, I found the USDA 75-8-9 had more scab on the shucks than USDA 75-8-5.  With more scab on the shucks, USDA 75-8-9 had poorer kernel fill than its sister clone. Note that USDA 75-8-9 has flatter, less-plump kernels.

     All three of the cultivars pictured in this post show kernel symptoms that point to a shortage of summer heat during the growing season. Even though all three cultivars split their shucks well before the first fall freeze, nut development was delayed by cool mid-summer temperatures and kernel filling process simply ran out of time as fall approached.

What happens when Lakota over-produces?

    As a pecan cultivar, Lakota has a lot of great attributes. Lakota produces large pecans with high quality kernels. The tree is precocious, high yielding, and scab resistant. However, Lakota is not the perfect cultivar. As the tree ages, Lakota can over-produce and slip into alternate bearing.   
    Our Lakota trees are now close to 30 years old and this past summer the trees were loaded up with pecans (photo at right). Lakota can produce large nut clusters often with six to seven nuts to a cluster. Although large cluster size looks impressive in mid summer, too many nuts in a cluster usually creates problems with kernel fill.

    In the photo above, the four kernels on the right side are examples of the excellent quality nuts  usually associated with Lakota pecans. The four kernel halves on the left side also came from Lakota nuts but illustrate the common kernel defects associated with crop over-production.  If you look carefully you will spot three indicators of poor kernel fill. 

    First, note that the kernels on the  left do not appear as plump as the kernels on the right. In addition, the poorly filled kernels have a light coat of fuzz on the surface of the kernel especially towards the apex. Turn the kernel over and you see that the underside looks hollow or depressed. All three of these symptoms are indications that the tree did not have enough available energy to fill every nut on the tree to maximum quality.

    The biggest problem with over-producing Lakota trees is the fact that a single tree produces both high quality and lesser quality nuts. This can create a marketing nightmare especially when selling directly to the consumer. Ultimately, over-production can be managed by thinning the nut crop in mid-summer using a trunk shaker. Shaking over-loaded trees during the water stage of nut development will reduce both the number of nuts per cluster and the number of nut clusters per tree. By reducing the crop load, the remaining nuts will fill to perfection and the tree will set a better crop the following season.      

Ice coats native pecan groves

    Last week we had 3 days of harvest-able weather conditions. All was going smoothly until our pecan tree shaker flew to pieces just as the weather was beginning to take a turn for the worse. Over the weekend we had a little over an inch of rain including a quarter inch of ice accumulation. This morning the sun finally broke through the clouds making our ice covered native pecan groves sparkle (photo above).

       We still have pecans to harvest (photo at left), but it looks like the ice won't be melting off the trees until Christmas day. After that,  the ground will need to dry before harvest can resume. While we wait for harvest conditions to return, we will be busy repairing the shaker (and trying to stay warm!).

Kanza production 2013

2013 Kanza Crop

     I've been recording the yield of a 3 acre block of Kanza pecan trees over the past several years. In 2013, we had a nice crop of good sized nuts with the yield bouncing back following two years of drought. The yield of for these trees over the past four years is given below.

----------------------------------
Year   Tree age   Yield (lbs/acre)
-----  ---------  ----------------
2010      15         1050
2011      16          899
2012      17          810
2013      18         1028
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    This winter, we will be thinning additional trees from this orchard according to our thinning plan.

Finally! Pecan harvest resumes

    Over the past couple of days the pecan harvesters have been humming over the native pecan groves of Southeast Kansas. After weather delays due to rain and snow, soil conditions were finally favorable enough to pick pecans. Yields in the area are good, not great. Plentifully rain during midsummer of 2013 has meant that nut size and kernel fill are outstanding this year.
     Unfortunately, another winter storm is headed this way for the weekend. The weather man is promising rain, ice and snow. It looks like the 2013 harvest season will be stretching well into 2014.  

Double-row pecans: Pecan yield at year eleven

   Earlier this fall I posted a photo of the trees in our double-row pecan planting (photo at right). A couple of weeks ago I harvested the nuts from these trees and recorded yields for each of the three cultivars in the trial. 
     In establishing this orchard, we grafted Faith, Gardner, and Lakota during the years 2005-2007 onto Colby seedling rootstock trees that had originally been planted back in the fall of 2002. Below is a chart of this year's average yields.

-----------------------------------
Cultivar      Lbs/tree    Std.Dev.
------------  ----------  ---------
Faith           8.16       1.24
Gardner        10.03       2.00
Lakota         20.01       3.18
----------------------------------- 

 
   The trees in this trial are still young, averaging a little less than 4 inches in trunk diameter. The Lakota trees actually over-produced for their age resulting in less-than-stellar kernel quality. The 10 lbs. per tree yield produced by Gardner seemed just about right for this size tree. Both Faith and Gardner produced excellent quality nuts.
   On a total land area basis, the double-row planting plan has 27 trees per acre. Per acre yield for 2013 ranged from a low of 220 lbs/ac for Faith to a high of 540 lbs/ac for Lakota. 

Snow stalls pecan harvest

   A two inch blanket of snow fell on our pecan grove last night putting a halt to our pecan harvest. Weather delays are a part of pecan farming that I've come to accept. So instead of cursing the weather, I decided to enjoy the moment and take a few "artistic" photographs (below). There is no place on earth more beautiful than a pecan grove.

 

Pecan: A standout among hickories

   There are eleven species of hickory native to North America and yet the pecan is the only member of the Carya genus that has been developed into a commercially viable orchard crop. Ever wonder why?  It's not all about taste. Sure some of the hickories produce bitter kernels, like the bitternut hickory (Carya cordiformis) and the water hickory (Carya aquatica). However, the shagbark hickory (Carya ovata) produces a sweet, oily kernel that has a delightful flavor.

    What makes pecan (Carya illinoinensis) stand out among all the hickories is a unique shell architecture that makes extracting the kernel much easier. To illustrate the major differences in shell characteristics between pecan and a typical hickory nut I'll be using photos of Kanza pecan and Fairbanks shagbark hickory (photos at right).
   

      I used a bandsaw to carefully slice through a pecan and hickory nut to reveal, in cross section, the relationship between kernel and shell (photo at left). The red arrows point to the portion of the nut's shell that protrudes into the dorsal grove of each kernel. Note that this protrusion in the hickory is basically an extension of the hard outer shell. In sharp contrast, the material that protrudes into the dorsal grove of the pecan is composed of loose packing material rather than shell material.
    This major difference in shell structure becomes obvious when cracking each nut. When a pecan is cracked the material inside the dorsal groove breaks free from the outer shell easing the extraction of kernel. When cracking a hickory, the shell's protrusions into the kernel remain firming attached to the outer shell and can trap portions of nut meat inside of shell fragments.
    The yellow arrows, in the photo above, point to the inner wall partition of each nut. Note that this inner wall in the hickory is composed of the same hard material as the outer shell. In pecan, the inner wall is softer packing material similar to the material found inside the dorsal groove. When a pecan is cracked the inner wall breaks free from the outer shell allowing both kernel halves to fall free of the shell. In contrast, the inner wall partition inside a hickory nut is not easily separated from the outer shell wall during the cracking process. Often, when cracking hickory nuts, the inner wall will trap one of the two kernel halves requiring a second crack to fully remove all the kernel.

     There is one more difference between pecans and hickories that makes pecan easier to shell. In the photo at right, the red arrows point to cleft in the kernel of each species. This is the location of a  secondary inner wall partition that runs perpendicular to the main inner wall seen in the cross-section photos above. The secondary inner wall in hickory is quite prominent and extends deeply into the kernel. This secondary wall is also composed of hard outer shell material that can trap kernel fragments inside broken bits of shell during the cracking process. In pecan, this secondary wall is greatly reduced or not present at all. In cracking a pecan, the secondary inner wall partition may appear as a small sliver of packing material lodged in the tip of the kernel. However, this bit of inner shell material usually falls free of the kernel during commercial shelling. 
    

Cultivars that ran out of time to fill kernel

Maramec 2013

   The 2013 growing season in SE Kansas was shorter, wetter and cooler than average. While early-ripening, pecan cultivars have produced high-quality pecans this year, cultivars that ripen late in season are displaying some serious kernel quality issues.
    During this past summer, I posted photos of the development of Maramec pecans as compared to the earlier ripening cultivars Osage and Kanza. Now at harvest we can see the end results of Maramec simply running out of time to fill kernel (photo above).
    Both kernel halves in the photo came out of the same Maramec nut--a nut equal in size to the whole nut pictured next to the kernels. The kernel on the left looks normal but is only 3/4 the length it should have been. The kernel on the right is flat and misshapen. Both kernel halves have patches of fuzz attached to the surface. If you were to snap one of these kernels in half you would find air spaces inside the kernel. The kernels lack oil and taste like cardboard.
   

Stuart 2013

    Stuart also ran out of time to fill its kernel this year (photo at left). The kernels are short. The kernel halves are shriveled on the ends and the surface of the nutmeat is fuzzy. These are all symptoms of a Stuart nut that did not receive enough heat and length of growing season to properly develop a quality kernel.