Be careful when pulling off stalked buds

    Yesterday, I spent the morning trimming grafts and training the scion to a nice central leader.  Just two weeks ago, I worked on these same trees selecting a single scion shoot and removing stalked buds. However, it is amazing how fast bark grafts can grow. Many grafts had grown 10 to 12 inches taller in just two weeks. Along with the new growth, the tree also developed new stalked buds (red arrows point to stalked buds in photo at right). My first step in training these grafts is to remove all stalked buds. Next, I used flagging tape to tie the new growth to the bamboo stake I already had in place.

    When I remove stalked buds I always start at the top of the scion shoot and work my way down. At some point, I will come the location on the shoot were I had removed stalked buds previously (2 weeks ago in this case). You need to watch carefully as you tear off the stalked buds. In the photo at left, the red arrow points to a stalked bud that has developed since the last time I removed stalked buds. This bud will be removed.
    The yellow arrow points to a brown scar on the stem indicating the position of a stalked bud that I removed 2 weeks ago. Below the scar is a secondary bud that is starting to grow. I will leave this bud in place to form a wide angled lateral branch. Remember, by the time a secondary bud starts to break, it will be located well below the central leader and in perfect position for lateral branch formation.
   

Be careful to remove the right buds during young tree training

   In several posts on this blog, I have stresses the importance of removing stalked buds from rapidly growing young trees to encourage the growth of a strong central leader tree.  The photo at right shows the terminal portion of a tree I grafted this past spring. Note that the primary buds in each leaf axil have already formed a long stalked bud. By removing all these primary buds near the apex of the tree, I can force the tree to remain focused on growing a single central leader. Pruning out stalked primary buds effectively delays the tree from developing lateral branches in the pruned area for 3-4 weeks. This allows the central leader to grow taller, staying well above later developing lateral branches.

    However, my emphasis on removing stalked buds may have caused confusion among some growers. The photo at left shows the same tree as the one pictured above. However, this photo shows the central leader of my new graft about 2 feet below the apex. Here you will note a short stump hovering over a growing bud in each leaf axil. This stump was left behind when I pruned out a stalked, primary bud 3 weeks earlier. Now the secondary buds are starting to grow out, looking like slightly shorter versions of those dreaded stalked buds. Here's where the confusion comes in. Don't feel the urge to rip off these secondary buds just because they appear to be stalked.
    These secondary buds were fully sessile when they were formed. But at this point in time, the secondary buds are pushing out to grow new lateral branches. And since these new shoots are forming about 2 feet below the central leader's terminal, you should let them grow out.
   The art of young tree training is an act of making sure a tree achieves balance between growth of the central leader and the development wide-angled lateral branches. Allowing secondary buds to grow and produce laterals is an important part of that art.    

Notes of this year's grafts

   Over the past couple of weeks, I have been trimming and training my successful grafts. The new growth I've seen on my grafts this year have been outstanding. The photo above is just one example of a tree I grafted with a Kanza scion placed on a 1.5 inch diameter seedling pecan tree using a bark graft. Before I shot this photo, I removed all rootstock suckers, pruned the graft to one shoot, removed stalked buds, then tied the new shoot to a bamboo stake. I protected the entire tree from deer with a 5 foot tall welded wire cage.

   In trimming this tree, I noticed a couple of things that I thought important to point out. The first has to do with the small piece of grafting tape I tied around the scion. I applied the grafting tape to seal in the moisture inside the plastic bag that surrounds the graft union. But look how thin the 1/2 inch tape has already been stretched by the rapidly growing scion. The original scionwood I placed on the tree was roughly the same diameter as the pruning cut you now see at base of this year's green growth.  In just 6 weeks time, the scion stick has  increased in diameter two fold. To prevent possible girdling by grafting tape, I removed the tape but left all other graft wraps in place (photo above).

   In previous posts, I have written about the tree training problems that can be caused by allowing stalked buds to develop on a tree's central leader. I have usually associated the appearance of stalked buds with the growth of young trees but I've never before have I seen stalked buds develop on a new graft--that is until this year.
    At right is a series of four photos that show the buds growing on the graft shown at the top of this post. The first photo (at right) shows the buds on the lowest portion of the scion's new shoot. Here the buds appear small and tightly appressed to the stem.

    Moving up the stem, I found that the lowest bud pictured in the photo at right was small and tight to the stem. However, as I looked up the stem the buds started to develop short stalks.




 












    Further up the new shoot, stalked buds were longer and looked like they might start sprouting leaves soon (photo at right). If I allowed these buds to remain on the tree, it wouldn't be long before the tree would develop a brushy top with no clear central leader and numerous narrow-angled branches.
   Could it be, that I've just discover the origin of the phrase, "nip it in the bud"? I had to nip off these stalked buds before they could create tree structural problems.

    Finally, I looked at the very top of the new shoot (photo at right). Here I found that stalked buds were developing at the base of leaves that were still expanding. Amazing!
  In training this new graft, I removed every stalked bud on the scion's new shoot, from top to bottom. In 2-3 weeks, I'll revisit this tree, pruning where needed and pinching out any new stalked buds that form.

Time for new graft training

  

    Now is a good time to start training your successful grafts. Today, I worked on a couple of bark grafts including the tree pictured at right. After removing the deer cage, I cut off all sprouts growing from the trunk below the graft union. I next turned my attention to the shoots growing from the scion. I had left 2 buds on the scion when I grafted this tree and both buds had sprouted and were growing vigorously.
    

    In the photo at left, you can see that both scion shoots are about the same size in diameter.  I could choose to keep either one of these shoots to be my new central leader, but the straighter growth of the shoot on the right gives it a slight edge.  I then cut out the shoot on the left.

    With just one cut, I have established a new central leader for this tree (photo at right). Now all of the tree's energy will be focused into growing the scion's single remaining shoot.

    Like all vigorously growing pecan shoots, the shoot that I kept to become my new central leader was already producing stalked buds (photo at left). To prevent these stalked buds from growing into branches that form serious bark inclusions, I broke off every one of them. Breaking off stalked buds will also help preserve the dominance of the new central leader.

    My next step was to cut off the grafting tape that holds the plastic bag tightly around the scion. The scion on this bark graft should grow rapidly in diameter this summer and I don't want the tape to girdle the scion. After cutting and removing this small piece of tape, I will leave the rest of the graft wrappings in place for now.

    Next, I replaced the bird perch on the graft with a much longer bamboo stalk. I used electrical tape to attach the bamboo to the trunk of the stock, then used flagging tape to tie the new growth to the stake (photo at left). Bark grafts are easily damaged in the wind, so tying the new growth to a stake is a critical part of the graft training process. My final step, was to place the deer cage back over the tree. (No browsing deer is going to ruin this graft!)

Summer training a bark graft

    A bark graft placed on a large tree can grow very fast. Today, I returned to the tree I had  topworked this past April for some additional directive pruning. Just 4 weeks ago, I pruned this graft to a single central leader and now the new leader has grown to nearly 5 feet tall (photo at right).

    The graft has also grown in girth. The photo at left gives you some idea of how much this graft has grown. The original scionwood I placed for this graft was about 3/8 of an inch in diameter. Now that scion is almost 1 inch in diameter and still growing.
    Note the size of the central leader compared to the size of the lateral branch I pruned off the last time I visited this tree. Four weeks ago all the shoots growing from the scionwood stick were roughly the same diameter. Now, with all the tree's energy focused on just one shoot, my central leader is becoming well defined.

   To maintain the growth of a strong central leader, I spent some time to remove stalked buds and practice the two foot rule for pecan tree training.  Looking over the central leader of this new graft, I noticed that stalked buds became more prevalent and further extended as I looked up the stem (photos above). Left alone, these stalked buds would have grown into branches, giving the tree a overly-heavy, bushy top that is more prone to wind breakage.

    Caught early in their development, stalked buds are easy to remove. I just break them off with my fingers (photo at right). I took me just a few seconds to clear the entire central leader of stalked buds. Those few seconds were a great investment, saving me from having to spending hours trying to prune out the weakly attached lateral branches with bark inclusions that would have developed from the stalked buds.

     The final step in today's tree training operation was to place an additional tie to attach the central leader near the top the 2 x 2 inch post (photo at left). I may have needed a step ladder but I sure don't want to loose such a strongly growing graft to the winds of a summer thunderstorm     
 

Removing stalked buds

    We have been summer pruning the young trees in our orchard this week and find ourselves removing lots of stalked buds.  Both primary buds (upper bud at each node) in the photo at left are elongated and held on a short stalk. Allowing these stalked buds to grow into branches will create a tree with narrow, weak crotch angles (read this previous post for a detailed explanation of the problems stalked bud can create).
   At this time of year stalked buds seem to break quickly after they form and start to form new branches. Below are before and after photos demonstrating the removal of stalked buds. On the left side you can see stalked buds that have grown into branches at every leaf node. The stalked buds I removed are marked with the letter "R". There is one stalked bud I decided to save (marked with a "S") because this bud was located at the very top of the tree and represents the growing point for my central leader. After pruning I have preserved my central leader and prevented the tree from developing a leaderless, bush top (right side of photo).

Training young pecan trees: The problem of stalked buds

    Early summer pruning and the forcing of rapid central leader growth can promote the development of stalked buds. Stalked buds are primary buds that form on short stems (photo at right). If stalked buds are allowed to grow into lateral shoots they will form a weak branch attachment characterized by a bark inclusion. The best way to explain how stalked buds grow into problem branches is with a series of photos.

    Here is a stalked bud that has started to grow and is now 8 inches in length (photo at right). Notice how a bark inclusion is already starting to form on the upper side of the shoot. Also in the photo is a leaf petiole (below the stalked bud shoot) and a secondary bud (between the stalked bud and petiole).

     Allowed to grow much larger, a stalked bud develops into a branch with a weak branch attachment and deep bark inclusion (photo at right).
    Weakly attached lateral limbs should be avoided when training young pecan trees. Limbs with deep bark inclusions tear easily from the tree, creating a huge scar on the trunk. In addition, when limbs with a deep bark inclusion are pruned off during normal "limbing up" operations, the pruning wound left behind does not callous over well. Without a well defined branch collar, the tree has a hard time growing over the bark inclusion.

     If you prune a pecan tree during the spring to force the growth of a central leader, by June you should see strong growth and the development of stalked buds (photo at left). This central leader has grown over 2 feet in height since I pruned to a single leader 5 weeks earlier and all this new growth is covered with stalked buds.

    Here is a close up of the same central leader. Notice that some of the stalked buds have even started to grow into lateral branches. The good news is that if you continue to practice the 2 foot rule you should end up pruning all of the stalked buds off the central leader. Often times the stalked buds are so green and tender that you can just pull them off by hand without using a pruning shear.

     As the tree continues to grow., you should note that the lateral branches that develop below your 2 foot central leader are actually developing from secondary buds left behind when the stalked buds are removed. Note in the photo at left you can see the pruning wound left behind after removing the stalked primary buds. Below that, secondary buds have broken and developed into well angled lateral shoots.

    The next post in the training young trees series is When to start training

Stalked buds and branch attachment

    I mentioned the term "stalked bud" in my last post and this morning I thought it might be a good idea to show you exacting what a stalked bud on pecan trees look like. The development of stalked buds is most prominent on fast growing trees, so my hunt for buds to photograph started in our scion wood block. The trees in the scionwood block are severely cut back every spring to provide scionwood to growers across the area. This means that trees grow extremely fast in response to the heavy pruning often creating lots of stalked buds. The photo at left was taken  of a Colby tree. In the photo, you can plainly see the green leaf scar on the stem. Above the leaf scar is the secondary bud and above that is a "stalked" primary bud. Stalked buds are not usually associated with the Colby cultivar but under the right growing conditions any cultivar can produce stalked buds.

    On that same Colby tree, I noted a stalked bud that had begun to grow into a side shoot. In the photo at right, the leaf petiole is still attached to the branch. Above the petiole is the secondary bud and above that is the stalked bud that has started to grow into a side shoot. This shoot was about 8 inches long and you can already see the development of a bark crevice on the upper side of the branch attachment. This crevice will only get more prominent and deeper with each passing growing season. So when I'm doing summer pruning of young trees, I always make sure I remove all stalked buds as soon as I see them. It seems so much easier to pinch out a stalked bud than try to prune out a branch with poor branch attachment 3-4 years down the road.

Branch Attachment

 

    I was picking nuts from the young trees planted all around my house, when a came to a Kanza tree that just screamed at me to take its picture. Not for all the nuts it was producing but for the extremes in branch attachments I could see, all on the same tree. The lowest branch on the tree (above left) had the classic worst case scenario for a branch attachment--a deep crevasse on the upper side branch union. These kind of branch attachments are very prone to breakage and often lead to massive trunk tearing when the limb breaks out. Further up in the tree all the branches had picture-perfect,  branch attachments displaying a textbook version of a strong branch collar (above right). The question is, how did these branches form and is there anything that can be done to encourage strong branch angles?

    I noticed when training these young trees that fast growth rate promoted the development of stalked buds (buds on the ends of stem like projections) in the upper portion of the tree. By mid-summer these stalked buds were all starting to sprout and I had to remove all of these new shoots to maintain a strong central leader. Leaving a stalked bud to grow is a big mistake, because the branch that forms from this bud will produce a branch attachment like the bad one pictured above-left.  By pruning off the stalked buds, I forced the tree the sprout from secondary buds the following spring. When these buds grow they tend to make great branch attachment unions. In the case of my Kanza tree, it looks like I missed a stalked bud early in the life of my tree. This problem branch will not be a problem much longer--I'll be removing this branch early next spring.