Grafting time

Preparing a scion for grafting

     During a normal year, I usually starting grafting pecan trees during the first week of May. However, last week (the first of May) we received over 7.5 inches of rain during the course of the week and the Neosho River spilled over its banks flooding a large part of my pecan grove. Needless to say, my 2022 grafting season got off to a late start. 

    This week, summertime temperatures and ample sunshine dried the fields enough to make getting out in the field to graft trees possible. One of the biggest mistakes novice pecan growers make in grafting trees is  attempting to place a graft on a tree that is too small and does not yet have a well established root system.  My rule of thumb is to never graft a tree unless it grew at least 2 feet of new shoot growth the previous growing season.

   The tree pictured at left is ideal for grafting. By the time a pecan tree has achieved this size above the ground, the root system is extensive and features a massive tap root.  

 

   I usually graft this sized tree at about 20 to 24 inches above to soil (photo at right). I choose this height for two reasons. First, 20 inches is a comfortable working height for me while I sit on my cooler to carve the scion and place the graft. Secondly, removing a majority of the top will force the tree to focus all its energy on pushing shoots that sprout from the scion. Ultimately, the rapid growth that results from such drastic pruning is easy to train into a strong central leader trunk.  

  The tree I selected for grafting is roughly one inch in diameter at the point I made the cut (photo at left). I like to use a bark graft in this circumstance. Once the graft starts growing it won't be long until new wood growth completely covers over the wound I made on the seedling rootstock.

 

    For a small diameter bark graft, I choose a small diameter scion to insert under the bark (photo at right). If you would like to see a more detailed discussion of how to make this graft, check out a previous post HERE.

   I always attach a bamboo stake to the tree after I've completed the graft (photo at left). Initially, this stake protects the scion from bird damage (perching birds can break off the scion). Once the scion breaks bud, I tie emerging shoots to the stake to train the new growth and to prevent wind damage. 

     This photo also reminds me that I've been using the same grafting box for 40 years. It has served me well.

     Deer populations in Kansas have exploded to the point where I never leave a young tree uncaged.  The cage protected the seedling the entire time it was growing into grafting sized tree. Once grafted, the cage will remain until the young tree has grown limbs well above deer browsing height.   At that point, I remove the cage and place a trunk protector on the tree to prevent buck rub.

Pecan leaf burst and first signs of pollination season

Kanza leaf burst, 26 Apr 2022

      Last week I was able to photograph several pecan cultivars as new spring growth emerged from long-dormant branches. As buds break, you should note the strong apical dominance of new shoot growth that is characteristic of pecan trees.  In the photo at right, new shoots and leaves sprout primarily from a cluster of terminal buds that developed as shoot growth slowed to a stop during the summer of last year.  Further down the stem, you will note that buds have broken open but seem to only produce male flowers or catkins. This is a consequence of apical dominance. The buds at the terminal of the branch break first and their growth sends a hormonal signal down the branch to suppress the development of  vegetative buds lower on the branch. 

    For sexually mature pecan trees, each primary bud on last year's shoot contains a central vegetative bud and two lateral male reproductive buds. Note that each male reproductive bud produces 3 catkins. As terminal growth continues to expand the hormonal signals become so strong that it causes central vegetative buds lower on the stem to abort from the tree. The catkins, however,  remain until they complete pollen shed later in May. 

Gardner, 26 Apr 2022

    As I moved through my orchard, I observed obvious differences between cultivars in terms of bud development and the appearance of catkins. Some trees appear to produce catkins well before new shoot growth. This occurs with protandrous pecan cultivars like Gardner (photo at left).

    Pecan trees have one of two flowering habits. Trees that release pollen before their female flowers become receptive, have a protandrous flowering habit. Trees that produce female flowers that are receptive to pollen before they release their own pollen are termed protogynous.  

   Over the years, I have also noted that the catkins on protandrous cultivars appear short and fat while catkins on protogynous cultivar are much longer and narrow.

Labette, 26 Apr 2022

    The photo at right is of a  Labette shoot and is typical of the early Spring appearance of a protogynous cultivar. Note how far the leaves have expanded in contrast to the Gardner shoot pictured above. Catkins on Labette have also emerged but they are not nearly a prominent as the catkins on Gardner at this point. However, note that even though Labette catkins are still enlarging they are already longer than Gardner catkins.

    During my tour of the orchard I noted two cultivars that had significantly later bud development.  Both Liberty and Hark are protandrous cultivars. Liberty appears to lag several days behind the leaf burst of other protandrous cultivars. In striking contrast, Hark leaf burst is far behind all other cultivars on my farm. Late leafing is a desirable cultivar characteristic for a pecan cultivar when grown in areas with a high risk of late Spring frosts. 

Bud Break and Spring Fertilization

Kanza buds 14 April 2022

    As I have mentioned in previous posts, I like to time the application of fertilizer to my pecan grove to coincide with the very first signs of tree bud growth. We've had a cool spring in SE Kansas this year which has delayed the bursting of pecan buds. Here we are in mid-April and our pecan trees still appear largely barren of new growth. However, on close inspection I've found some trees have started to push their buds open (Kanza buds pictured at right).  

    Seeing bud growth, I rented a fertilizer spreader and applied 150 lbs./ac urea and 100 lbs./acre K-Mag. K-Mag is a naturally occurring mineral that contains potassium (K), Magnesium, and Sulfur. In my pecan grove, previous leaf analysis results indicated that my trees were low in Magnesium. This is what prompted my switch to K-Mag rather than use the more common potassium fertilizer, muriate of potash (potassium chloride).

    The cost of all fertilizer materials have increased dramatically over the past 18 months, which has made many pecan producers pause to question; "Can I really afford to apply fertilizer this year?".  At first, skipping a regular fertilizer application will seem to have little effect on pecan yield. The yield for 2022 is largely programed in the tree before you ever make a spring fertilizer application. The negative affect of skipping a fertilizer application this year will come in 2023. Without adequate nutrient applications in 2022, the tree will drain all of its reserves to grow and mature the current nut crop. This will leave the tree unable to create the pistillate flower buds that will form the basis of the 2023 crop.  Ultimately, skipping a fertilizer application will increase a pecan tree's tendency towards alternate bearing.   

USDA 61-1-X  14 Apr.2022

   While scouting my orchard for bud development, I observed that not all cultivars were at the same stage of bud development. For example, USDA 61-1-X had swollen buds that looked ready to burst open (photo at right).

Hark 14 Apr 2022

    

 

 

 

 

    In sharp contrast, Hark buds appeared fully dormant (photo at left). Late bud break is a positive trait for northern pecan cultivars. A delayed start to shoot growth often allows late budding pecan trees to avoid late spring frost damage.

    As a general rule, pecan trees are one of the latest tree species to break bud in the spring. On the same day that I was scouting pecans for bud break, my apple orchard was in full bloom, buzzing with the sound of hard-working honey bees (photo above).

Cutting pecan scionwood

   

    Last week, the weather was perfect for getting outside and cutting pecan scions. On my farm, I have several trees that are trained specifically to grow high quality scions. The photo at left shows a Yates 68 tree that is covered with long, one-year-old shoots just perfect for making prime scionwood. 

    Depending on the weather, I usually starting cutting scions in late February or early March. The shoots at this time are still fully dormant and the buds are nice and plump.

 

    In the photo at right, I have cut all the one-year-old shoots off the right side of the tree. Note that I deliberately leave short stubs with each pruning cut. This will provide multiple buds for developing new shoots this spring, creating even more scionwood opportunities for 2023.

    Eventually, I prune every shoot off the tree (photo at left). This kind of drastic pruning practically eliminates nut production and retards overall tree growth. However, by limiting height growth, I can maintain a steady supply of easily accessible and healthy scions for years to come. 

     Once I have all the one-year-old shoots on the ground, I pick up the limbs and start cutting them into graft-size pieces. I store my scions is plastic tote boxes that feature tight-fitting lids. Before adding scions to the box, I line the bottom with 4 layers of paper towels. I then pour just enough water on the towels to soak them fully. I cut scions 5 to 7 inches long with each stick having at least 3 buds. I carefully stack the scions in the box making sure not to dislodge buds from the sticks. Once I fill the box, I place another layer of paper towels over the top of the scions and moisten with water. 

    The wet paper towels help to maintain 100% relative humidity inside the box, keeping the wood from drying out in storage. After attaching the lid of the box, I store the scions in a cooler kept at 34 degrees F.   At my location, grafting season starts during the last week of April or early May.