Wednesday, April 7, 2021

Pecan trees breaking bud

     Over the past week, I've been enjoying the spring weather by working in the pecan grove. Today, I collected terminal branches from several trees to illustrate the variation that occurs in time of budbreak between pecan cultivars. The photo below shows the stage of bud development for six pecan cultivars.  

 

    Greenriver buds were the most advanced with new leaves primed to unfurl. In sharp contrast, Hark buds were just starting to swell with their out scales recently split open.

   When folks look at variation among pecan cultivars they often try to make generalizations in terms of northern pecan cultivars vs. southern cultivars.  However, the earliest bud breaking cultivars shown above (Greenriver and Yates 68) are widely planted northern pecans. Lakota and Kanza are USDA creations that contain genes from both a southern cultivar and Major (a northern cultivar). Gardner and Hark are open pollinated seedlings of unknown parentage. From my experience, I have noticed an equal amount of variation in bud development among the native pecan trees that populate the Neosho River bottoms.   

    The timing of bud development has one important ramification. Trees that break bud early are more often damaged by late spring frosts. Over the years, I can clearly remember Greenriver buds suffering frost damage.   However, with cold enough temperatures, all stages of green tissue on pecan trees can be injured.
   

Wednesday, March 31, 2021

Springtime fertilizing


     Every Spring I fertilize my pecan orchard and today was the day I accomplished that task. Two factors go into my decision for timing the Spring fertilizer application. The first is bud development and the second is field conditions.  Fertilizer nutrients are most rapidly taken up by pecan roots during the Spring flush of root growth. When I see the buds of pecan branches start to swell and out scales begin to split open (photo above), I know root growth has begun.

    The second factor is field conditions. The ground must be dry enough to support the weigh of 4 tons of fertilizer being hauled in a spreader over the field. I also look at long term weather predictions to increase my chances of not letting flood waters leach away all my applied nutrients.

    This spring I applied 200 lbs/acre of urea fertilizer (92 lbs/acre of nitrogen). I also applied 200 lbs/acre of a product called K-Mag. K-Mag is composed of the naturally occurring mineral,  sulfate of potash-magnesia. K-Mag contains 22% potassium, 22% sulfur, and 11% magnesium. In the past, I always used straight potash with my urea in the spring. However, since liming the orchard a few weeks ago, I knew the additional calcium (lime)  I added to the soil can inhibit magnesium uptake. By using K-Mag, I could add both needed potassium and increase soil magnesium levels.

   This summer I'll take leaf samples from my trees and send them off for analysis. By mid summer, I'll have the data to see how well these soil amendments preformed.

Sunday, March 14, 2021

Spreading lime in a pecan grove


     Using soil tests, I discovered that the soil in my pecan grove was more acid than ideal (pH < 6.0).  Pecan trees perform best in soils that have a pH above 6.5 but below 7.2.  So, this spring, when the soil in my grove was dry enough to allow a large and very heavy lime truck to travel between trees, I had 6 tons of lime broadcast per acre (Photo at right).

    Typically, when lime is applied to agronomic fields, cultivation is used to help mix the lime into the soil profile. Mixing the soil after liming helps to moderate the soil pH throughout the crop's rooting zone. But in a pecan grove, cultivation is not an option because it would destroy all the tree's fine feeder roots. 

     I used an implement called a pasture harrow (photo at left) to break the surface of the soil and lightly rake the lime into ground. I'm not sure how well the harrowing helped in terms of lime incorporation but based on the experiences of forage producers, harrowing should help my cover-crop flourish. 

    This summer I plan on taking both soil samples and leaf samples to see where I stand in terms of soil fertility and tree nutrition. The results of those tests should tell me if the investment in liming was beneficial.

Saturday, March 6, 2021

Harvesting pecan scionwood

      All this week, I've been busy cutting pecan scionwood from trees that were specifically trained to produce long one-year-old shoots. The photo at right is just one of several scionwood trees I have growing near my home. Notice the many long, light-colored shoots produced by this tree especially at the top of the canopy. The pruning technique I used to create this rapid shoot growth has an old world name -- pollarding.

    The radical pruning of a tree (pollarding) is an ancient practice use to produce long limber sticks that could be used to weave fences to control grazing livestock, to make baskets or to burn as firewood. The Vincent Van Gogh painting at left depicts a typical rural scene of rows of pollarded trees. Pruning cuts were made above grazing height to prevent cattle, sheep, and goats from feeding on tender new shoots as their emerge in the spring.

 

     I've haven't taken up basket weaving in my retirement, but I still cut all the one-year-old shoots off my scionwood trees reminiscent of my European ancestors (photo at right). Once I get all the shoots to the ground, I then cut the shoots into 7-8 inch long scions.

   Pollarding pecan trees produces excellent scionwood. The shoots are vigorous, have widely spaced buds and have ample stored carbohydrates ensuring maximum graft success.


     As I cut the shoots into scions, I make certain that each stick has strong healthy buds. The photo at left shows the typical primary, secondary, and tertiary buds that can be seen above each leaf scar on a pecan twig. I always make sure to have at least two sets of buds near the top of each scion stick.

  


    The rapid shoot grow associated with pollarding pecan trees often stimulates the production of stalked buds (photo at right).  In preparing my scions, I always prune off stalked buds. These long buds often get broken off during storage and handling. If they remain, they can puncture the plastic bag used to store and ship scions increasing the potential for scionwood desiccation. As you can see in the photo, a strong secondary bud sits just below the stalked bud and will provide a great growing point for a successful graft.

       The photo at left illustrates the quality of scions cut from trees specifically pruned to grow vigorous one-year-old shoots. The larger diameter scions I typically use for 3-flap grafting. I like to use smaller diameter scions for bark grafting.