Saturday, May 25, 2019

Forcing a new pecan graft

     Between rain showers, I have been inspecting all the grafts I made earlier this Spring. New buds on the scions are emerging but stump sprouts are trying to over take the scion. The photo at right is a typical example of what I'm seeing in my orchard (photo at right). Hidden between vigorously growing stump sprouts are 2 new shoots growing from the scion. Note that the stump sprouts have red pigmented leaves and stems typical of juvenile pecan tissues. The buds emerging from the scion are green in color (an indication of sexually mature tissue). If this graft was ignored from the rest of the summer, the stump sprouts would grow so rapidly that they would shade out the scion shoots causing the scion to die from lack of sunlight.

    On this first visit to all my grafts, I prune off all stump sprouts if the graft shows any sign of life. Trimming off the stump sprouts takes only a minute but serves push the scion shoots to grow faster (photo at left). This process is generally known as forcing the graft. I view it as directing all the tree's energy into healing over the graft union and growing a vigorous new central leader.
    If you look closely at the two buds growing from the scion you will notice that the lower bud seems to be more advanced than the upper bud. This is a very common occurrence. It seems that the bud closest to the the graft union seems to get a greater of the rootstock's energy, resulting in a faster growth rate.  At this point, I'll let both buds develop into new shoots because you never know if some creature will destroy one of the tender shoots. In 3 weeks, the new shoots will have developed some woody tissue and I can select the strongest shoot to become my new central leader while pruning off the weaker shoot.

Wednesday, May 22, 2019

Third flood this year on the Neosho River

   Over the past 3 weeks, we have received over 14 inches of rainfall--That's one third of our normal annual total. Within this same period, the Neosho River has spilled over it banks 3 times. Currently, the water is still rising (photo above) with the crest not occurring until sometime Friday. This current flooding event is predicted to rival the flood we had in April of 1994; the fourth highest flood on record.

    My pecan orchard is located over four miles from the Neosho but river water has backed up and is covering the ground under my young Kanza trees (photo above). Fortunately, pecan trees can tolerate flooding and even grow best in flood plain soils. In time, the water will recede but I'll be left with a mess to clean up. It's always amazing to see what a flood can float onto the orchard floor.  Once the ground dries up, I'll get it cleaned up with a tractor and rake. 

Friday, May 17, 2019

First buds to pop on 2019 grafts

    Today, I start on a long drive to Indiana to teach pecan tree grafting to some eager nut growers. But before I jump in to the pickup, I decided to take a photo of one of my 2019 Kanza grafts just to remind folks that grafting pecan trees is one of the most rewarding aspects of starting a new pecan orchard. I am always amazed how I can place a dormant piece of scionwood on a stock tree and just a few weeks later the buds pop and the countdown to nut production begins.
   I'm looking forward to meeting both old and new friends in Scottsburg this Saturday (May 18). Click on the events tab above for details and come join us.

Thursday, May 16, 2019

Pecan pollination half-way complete

    Today, I checked pecan flowering to see how things were progressing. My first stop was a Gardner tree. As you can see in the photo at right this protandrous cultivar has shed all its pollen, the catkins have turned brown but have yet to fall from the tree. Hardly visible in the photo is a cluster of female flowers at the end of the new shoot.

  The photo at left is a close-up of a nearly receptive cluster of Gardner pistillate blooms. The bright red stigmatal surface of Gardner flowers really make these blooms easy to spot.
    Next, I moved on to a protogynous cultivar--Kanza (photo at right). Kanza catkins have turned yellow in color and will begin opening soon to release pollen. If you look carefully you can spot a cluster of female flowers at the end of the new growth.

    Kanza pistillate blooms appear to be already pollinated (photo at left). The stigmatal surfaces of Kanza flowers are a light greenish-yellow. However, note that the tips of the stigmas have turned black which is a good indicator that these flowers have been pollinated.
   From what I have seen so far during this year's pollination season, the potential for a good nut crop look very good.

Tuesday, May 14, 2019

Waiting for grafts to break bud

   The sun has come out and daytime temperatures are starting to rise into the 80's. With this kind of weather, I start to get anxious to see my pecan grafts break bud. Today I visited the first graft I made this year (photo at right). This graft was made back on Wednesday April 24th; that's 20 days ago. As a rule of thumb it usually takes three weeks before the buds on a new graft start to pop. However, the first half of May has been unusually cold and damp. I may not have bud break yet but it looks like the buds on my scion have started to swell.
   Two weeks before I started grafting pecans, I grafted about 70 apple trees. Apple trees start growth earlier in the Spring (than pecans) allowing them to be grafted earlier (usually early April). My apple grafts weren't phased by this Spring's cool damp weather and all my scions are showing good growth (photo at left).
   I wanted to show you the difference in graft performance between pecan and apple to make a point about the nature of pecan trees. Pecan tree growth and graft callusing are enhanced by warm temperatures, especially high night-time temperatures. During the first two weeks of May average over-night lows dropped down into the 40's. Apple trees don't mind the cool temperatures and grew just fine. But pecan trees just seem to stand still in cooler weather.  
     However, this week we are forecast to receive ideal temperatures for pecan graft growth. Highs in the 80's and lows in the 60's. Pecan is a warm weather crop and seems to require higher over-night lows both to start growth in the Spring and fill out their nuts in the Fall.
     It won't be too much longer until I start to see new shoots developing on scions and the little green bud on the scion pictured at right will be growing like crazy.   

Wednesday, May 8, 2019

Spring blooms in a native pecan grove

   Over the past week, its been largely cloudy with frequent rain showers. I've recorded over 7 inches of rain in the past 8 days with more predicted to come tonight. With all this gloomy weather, I find it refreshing to enjoy this photo I took during a brief sunshine break we had a few days ago. To me, a native pecan grove is one of the most beautiful locations in the world and a place that always refreshes my spirit. 

Tuesday, May 7, 2019

Pecan pollination season begins

    Its that time of year when you can look up at a pecan tree and see thousands of catkins dangling from limbs (photo at right). Plentiful catkin production is a good indicator of a healthy tree but it is not related to the number of nuts a pecan tree will eventually produce. To determine the potential for a pecan crop this Fall, you'll need to inspect the terminals of the new growth and check for female flowers.
   When I checked my trees yesterday, I found that pistillate flowers on protogynous cultivars were easily seen and appear to be ready to accept pollen from a protandrous tree. The photo at left shows a cluster of Jayhawk female flowers. Each female flower is topped by a feathery stigmatic surface that is designed to capture pecan pollen out of the air. Below the stigma are four leaf-like sepals that stick out in right angles. Below the sepals is the pecan fruit that contains the ovule and egg. When a pollen grain lands on the stigma it germinates and grows down through the flower entering the ovule before  eventually uniting with the egg to form a new pecan seed.

     The catkins on protandrous cultivars were just starting to mature and release their pollen into the air. The photo at right shows some Gardner catkins that have just started to open their pollen sacs. As pollen sacs mature, they change color from green to yellow. As they dry in the sun, pollen sacs split open and release pollen. Once the pollen has been released the pollen sac will turns brown in color. As you can see, not all pollen sacs release pollen at once. Most pecan cultivars will release their pollen over a 5 to 6 day period.
    Even though they are not very prominent, you should be able to see the beginnings of  pistillate clusters on protandrous cultivars. The photo at left shows a flower cluster forming on the Gardner cultivar. Note that at the flowers are still tiny and not fully formed. By the time Gardner pistillate flowers become receptive they will be very large and topped with a bright red stigmas (that will be 10-14 days from now).
   There is one more observation you can make about pecan flowering at this time of year.  The photo at right shows a Kanza flower cluster. The red arrows point to fully formed and receptive pistillate flowers. At the terminal of this flowers cluster are 2 incompletely formed flowers (blue arrows). As pistillate flowers were  set on this new flowering shoot, the pecan tree actually ran out of resources to fully form the top 2 flowers. These ill formed flowers will eventually dry up and fall off the tree.

Thursday, May 2, 2019

Time for directive pruning young trees

    While I'm out grafting trees, I often pause at trees that I've grafted in past years to give them a little directive pruning to ensure that I maintain a central leader on rapidly growing grafts. The photo at right shows a tree that I grafted last year. I had 5 feet of new growth from the scion last summer and I developed a nice straight trunk. This year at budbreak, the very top of the tree exploded with dozens of new shoots all clustered at the very top of the tree. Left to grow unchecked, these news shoots would form a "crows foot" at the top of the tree and I would loose my central leader. A few snips with my pruning shears and I can direct all the tree's energy into growing a new central leader while at the same time encouraging lateral branching further down the stem. Let's take a look.
     My first step was to look over the very top of the tree (photo at left). I had new shoots growing every-which-way. At each bud node, the primary, secondary, and tertiary buds had broken and were developing into new shoots.
   As I looked down the stem, I passed over nearly 3 feet of dormant buds before finding a few buds breaking to form lateral branches (photo at right). This is how apical dominance works in pecan. The very top of last year's growth gets the greatest push for new growth. That growth, in turn, inhibits the growth of buds below the terminal via hormonal signals. When the hormonal signal weakens with distance this allows buds to break further away from the terminal. My goal in directive pruning is to reduce the negative effects of apical dominance on tree form and encourage both a central leader and the development of lateral branches.

    My first pruning cut was made at the very top of the tree. The terminal of this tree had at least 6 new shoots growing in tight competition. With a single cut, I began the process of isolating and developing a new central leader (photos above).

   To reduce the competition from shoots just below the new leader, I used my clippers to totally remove those shoots from the tree. (photo at left).
   By pruning the new growth at the top of the tree, I was directing all the tree's energy into my chosen central leader. However, my work was not quite done.

    I still had 3 shoots growing at the very top of the tree. With careful pruning I removed the shoots growing from the secondary and tertiary buds while leaving the shoot growing from the primary bud (photo above).

   When I finished pruning, my young tree looked sparser but I now had a single growing point at the top of the tree. And I know from past experience, that thinning out top growth stimulates the breaking of lateral buds to form the lateral shoots needed to fill out the canopy of the tree.

  I don't confine this directive pruning technique to just one-year-old grafts. The tree pictured at left was grafted 2 years ago and could also benefit from some directive pruning. To give you an idea of scale, the step ladder in the photo is four feet tall. I'll need that ladder to reach the top of the tree to make a few directive pruning cuts. 
   Note that the central leader of this tree has no lateral  branches for almost 4 feet below that little ball of spring growth at the top of the tree. Below that, the tree has developed a good framework of lateral branches. New spring growth on each lateral branch mimics what we see at the very top if the tree. New shoots are only growing from the apex of each lateral shoot.Here's how I pruned this tree.
    First, let's look the bud break from lateral shoots (photo at right). Proliferation of new shoots on the terminal of lateral shoots is a good thing. This will create an even greater leaf area for the tree to capture solar energy. However, I pay attention to the direction the new shoots are growing. I remove any new shoots that grow strongly upwards towards the central leader.
   Once I inspected the lateral shoots, I climbed up the ladder to address the new growth at the very top of the tree. Just like the tree in my last example, the very top of the tree is a jumble of new shoots with every new shoot competing for light. I pruned the top of this tree exactly like I did on the one-year-old graft discussed earlier (photos at left). 
      Pruning trees early in the season is one of the most important techniques for developing a well structured tree (photo at right). My goal is to make sure each tree in my grove develops single strong trunk. At the rate these trees are growing, it won't be too long before directive pruning the central leader will be out of my reach (I limit myself to using an 8 foot ladder). Once a tree grows too tall, I let the tree grow naturally. My only pruning at that point is to remove lower limbs to make working under the trees easier.