Friday, January 13, 2017

Branch growth pattern: Gauging the potential for native pecan productivity

    Recently, I took a short drive down the gravel roads in the Neosho River bottom to take a look at native pecan trees in mid-winter.  I passed native groves that have had a history of intensive management and then further down the road I came across groves that receive minimal or no inputs during previous growing seasons.  As I studied the canopies of native trees on this cold clear day, I noted striking differences in branch structure between well-managed and un-managed trees (photos below).

    The first tree I stopped at was located in a well manage native grove. What I mean by well managed is that this native stand has received fertilizer applications, both Fall and Spring, for well over 15 years. The grove is also sprayed regularly to control pests and the ground cover is both grazed and mowed. Choosing a tree at random within this grove, I looked upwards and photographed a portion of the tree’s canopy (above right).  Immediately, I noticed the numerous shucks that still hung from the branches. This tree produced a good crop of native nuts in 2016. But, I also noticed a vigorous branching pattern. The twigs within the canopy were long, thick, and light grey in color. This healthy growth pattern can only be appreciated after being compared to the branches of an un-managed native pecan tree.

    Down the road, I came to one of those native pecan groves that suffer from a lack of attention. If the trees in the grove look to be producing a few nuts, the orchard gets mowed and raked just before the harvesters come in to collect a meager crop of nuts. This grove has been starved of soil nutrients but is occasionally sprayed for pecan weevil control.  Again I picked a tree at random and took a photo of the tree’s branch structure (above left).  There was little evidence that this tree produced a nut crop in 2016.  The tree had short, thin branches that appeared dark in color. In comparing the canopies of managed and un-managed trees, it is almost hard to believe they are both the same tree species.

    After taking the photographs of tree branch structure, I used a pole pruner to cut a sample of twig growth from both trees (photo above). In the photo, the two dark twigs to the left of the ruler came from the un-managed grove. To the right of the ruler, I set down a single light-colored twig from the well managed grove. The reason I photographed two twigs from the un-managed grove is to give you some idea how poorly this tree bore nuts. Of the four terminals pictured from the un-managed tree, only one terminal had a pedicel attached indicating the formation of a nut cluster. Based on the size of the nut attachment scars on this one pedicel, I guarantee that all the nuts in this cluster were aborted by mid-season due to scab infection. In comparison, the branch from the well-managed tree displayed prominent pedicels on both terminals.  This twig had borne two nut clusters in 2016.

But the twigs pictured above have an even greater story to tell.  Note the diameter of the shoot growth. Un-managed twigs are thin and spindly. The twig cut from the managed tree has shoots that are longer and thicker. And here’s why this all matters. I can look at the branches of any native tree and predict its future productivity.  Branch growth is a reflection of total tree vigor. Vigorous thick shoots indicate that the tree will have the internal reserves to produce an abundant pistillate flower crop in the Spring.  Short, small-diameter twigs may produce a lot of catkins but female flowers will few in number.

   If you are still grumbling about a poor crop in 2016, take the time to go out and look at your trees this winter. If you don’t see vigorous branch growth, your native grove is not on the path of good annual nut production.  To increase annual nut production your first step should be to apply enough nitrogen fertilizer to stimulate the growth of strong, thick twigs. If the grove has been un-managed for several years, it will take several years of annual fertilizer applications (both Fall and Spring) to see a response from large native trees. Eventually, you’ll see better shoot growth and subsequently much better nut production.

Monday, January 9, 2017

In the eye of the beholder: Kanza and Pawnee

     Kanza and Pawnee are the two most popular pecan cultivars being propagated for northern pecan growers (photo at right).  The decision growers make to graft one or both of these cultivars is largely based on the expectation that the nuts they produce will command top dollar in the marketplace. However, the way growers look at pecan cultivars may be entirely different than the way consumers judge pecans.
   Consumers are visually oriented. Given the choice between several, in-shell cultivars most consumers will be attracted to the largest nut and immediately ask if the nut is a "paper shell". It doesn't seem to matter if a quality kernel actually resides inside the shell. Given the choice between Kanza and Pawnee, most in-shell buyers will choose Pawnee based solely on its larger size.

   Everything changes when the nuts are cracked (photo at right). Once a consumer can see the kernel, different visual cues come into play. Kernel color makes the greatest impression. In the minds of the consumer, a light, straw-colored kernel is associated with freshness. Dark or mottled kernels are associated with off-flavors even if the kernel is actually top quality.
    Kernel appearance is where Kanza really shines. A bag of cracked Kanza nuts is filled with plump, light-colored kernels. Cracked with a modern pneumatic pecan cracker, Kanza kernels not only look pretty but entire kernel halves are often freed from the shell.
    In comparison, Pawnee kernels vary widely in appearance, even when harvested from a single tree. Some kernels have a nice golden color while others appear mottled (photo above). This causes the consumer to pause and ask if the mottled kernels have something wrong with them. Offering a taste sample may be the only way to convince a consumer that a mottled Pawnee kernel tastes just fine.
   Its unfortunate that taste, that one human sense that should guide consumers,  is rarely used to select pecans within the marketplace. Both Kanza and Pawnee have excellent flavor, although their flavors differ. Kanza kernels taste sweet and oily while Pawnee kernels have a distinctive buttery flavor. Personally, I like the flavor of both nuts and I find it refreshing to switch up a recipe by simply using a different pecan cultivar.  

Tuesday, January 3, 2017

Stratifying pecan seed

   The beginning of a new year usually inspires folks to make plans for the future. I can't think of any better plan then to plant more pecan trees. So the very first thing I did in 2017 was to start stratifying pecan seeds that I plan to grow into new trees this summer.

   Stratification is the method we use to promote uniform seed germination. The process involves getting the seed nut fully hydrated then storing the moist seed in temperatures between 32 and 40 degrees F (0 to 4 degrees C) for 90 to 120 days. I started the process of stratification by placing some Giles pecans (2016 crop) into a 5 gallon bucket (photo above right).   

   I then added enough water to float the nuts inside the bucket (photo at left). To make sure the seed inside the shell becomes fully hydrated, I like to soak the nuts for 24 hours .

   To keep the nuts that float wet during the entire 24 hour soaking period, I placed a second 5 gallon bucket inside the first bucket and on top of the nuts (photo at right). By adding water to the upper bucket, the weight of the upper bucket presses down on the nuts below and keeps all seed nuts fully submerged.

    After 24 hours, I drained off all water from the seed nuts. As a precautionary measure, I added some Captan fungicide to the wet nuts and stirred the nuts around until each nut was coated with the white powder (photo at left). The fungicide will act to prevent kernel rotting fungi from destroying seeds during the cold stratification process.

    I use plastic storage boxes for seed stratification. I start by placing a layer of potting soil in the bottom of the box (photo at right). The potting soil is damp (not dripping wet!) and about 1.5 inches deep. By using damp potting soil, I ensure the nuts stay fully hydrated during the entire cold storage period.

  Next I add a single layer of nuts to the box (photo at left).

   I then add another layer of moist potting soil over the top of the nuts. At this point my small storage box was full and ready to be refrigerated. I you choose to use a deeper storage box, multiple layers of nuts can be added to the box. Just make sure to add potting soil between each layer of seed.

   One reason I like to use storage containers for stratifying seed is because the lids fit tight enough to prevent moisture loss during cold storage.  I place a label on each box with the cultivar name and the date the nuts begin stratification (photo at left). To achieve uniform germination pecan seeds need at least 90 days of cold temperatures. I use a standard household refrigerator to treat the seed and set the temperature to 34 degrees F (1 degree C).
    By April 2nd, these nuts will have had 90 days of cold treatment. However, I don't like to plant seed into pots until the danger of frost has passed. At my location, the average frost free date is April 20th. With an extra couple of weeks in the cold, these seeds should pop up quickly after planting.  

Wednesday, December 28, 2016

What happens when Kanza over-produces

   Kanza has been one of the best cultivars for our region. But no pecan cultivar is perfect. This past growing season (2016) was the first time I've seen Kanza produce too many pecans. The crop was so heavy on some trees that we saw upper limbs snap under the weight of the crop (photo at right). What was interesting to me was how Kanza responded to the excessive nut load.

    After harvesting our Kanza crop, I noticed that the size if the nuts was far more variable than in previous years (photo at left). Nuts differed is size from larger than average to very small. For the purpose of taking a photo, I combed through a super sack of Kanzas to find pecans that would represent the kind of variation I was seeing. The majority of nuts were medium sized however I definitely noticed a sprinkling of small nuts in the sack.
    To give you an idea of the variation in nut size I found I weighed the 8 nuts in the photo. The table below gives you my results. In looking over the numbers, its good to remember that our long term average for Kanza is 5.15 grams per nut. You can definitely see that I tried to pick out the extremes in nut size for the photo.

Kanza Nut Weights (g)
8.74        5.69
8.05        4.24
7.44        3.72
5.83        2.10

     Over production not only effected nut size but influenced kernel fill. In cracking out Kanza nuts this year I found most nuts were plump and perfect as usual. But, I also found kernels the had hollow looking undersides. It became clear to me that this year's Kanza crop was suffering from over production. However, how our trees responded to the overproduction is fairly unique among pecan cultivars. In my experience, trees that bear too many nuts respond in one of two ways; They produce a tree full of small nuts or all the nuts have normal size but the kernels are poorly filled. Kanza seems to do a little of both, while still producing a majority of nuts with high quantity. However, I've learned a valuable lesson in 2016. Like most improved pecan cultivars, Kanza would benefit from mid summer tree shaking to reduce excessive nut production.