Saturday, July 4, 2015

July 4th graft trimming

    For all those that have attended one of my grafting schools, here's a reminder that this weekend is a good time to trim up new grafts if you haven't already. Although I've been working on trimming grafts for over a month now, I still had a few that still needed attention. The photo at right shows a tree I worked on this morning. Three shoots have grown from the scion of this bark graft and two trunk sprouts have grown out just below the graft union. Time to get out the clippers.
    My first step was to remove all trunk sprouts below the graft union (photo at right).
    Next, I trimed the scion so only one shoot was growing fron the original scionwood stick (photo at right). In this case, the upper most shoot had the greatest diameter so I kept it over the others. Pruning the scion down to one shoot off the scion makes tree training much easier and helps develop dominant central leader.
   The final step in trimming up this graft is to remove the green grafting tape that holds the plastic bag tight around the scion. The scion stick will grow rapidly in diameter this summer and I don't want the tape to girdle the graft. I simply use a knife to cut the tape  but leave the plastic bag and aluminum foil in place.
   Next, I turned my attention to the top of the scion shoot. Stalked buds had formed on the new growth and I carefully removed each one by just pulling them off the tree (photo at right). With all the trimming complete, I tied the new growth to the bamboo stake using flagging tape to make sure I wouldn't lose the graft in a wind storm. And lastly, I placed a deer cage over the tree to keep the critters away.

Tuesday, June 30, 2015

Trimming up a bark graft placed on a stump sprout

   A couple of years ago we cut down several trees in our pecan scionwood orchard to make room for some new cultivars. Our idea was to cut a tree at ground level, allow it send up stump sprouts, thin the sprouts down to one strong-growing shoot, then graft that shoot the following year. The photo at right shows you one of the grafts I  made on a stump sprout this past spring. One one downsides about grafting a stump sprout is that for several years the tree will continue sending up new sprouts all around the outside of the stump. In the photo a profusion new shoots has grown around the base of my graft.
   The first thing I did was the break out my gas powered weed trimmer and carefully cut off all the new stump sprouts at ground level. You need to have a steady hand and a good eye to make sure you cut just unwanted sprouts and not injure the bark of the stem you are saving. Of course you can use hand clippers to do the same job, but I have found that a good strong string in my weed trimmer actually does a better job of cutting new shoots off at ground level or even a little below.
    The photo at left shows the tree once all the stump sprouts have been removed.

     After trimming off all sprouts that were growing on the trunk below the graft, I turned my attention to the graft itself (photo at right). On this graft, three shoots have developed from the scion. One shoot grew from the upper scion bud while two shoots developed from the lower scion bud. At this time of year I like to choose a single shoot growing from the scion to become my new central leader.
    I first looked at the shoot growing from the upper scion bud (photo at left). This shoot had a very confused growth pattern and was cover with long lateral shoots developed from the growth of stalked buds. This shoot looked like it would be difficult to train so I  decided to prune this shoot off immediately.

   After pruning the scion back to the two  lower shoots (photo at right). I could see that either one of these shoots would make a good central leader. The shoot on the left had a slightly larger diameter so I chose to make it my new central leader while pruning out the other.

    When you graft onto a stump sprout there is a lot of root energy pushing the graft to grow extremely fast. As a result the tree will develop stalked buds a every leaf axil (photo at left). Now that I had pruned the tree down to a single shoot, I carefully pulled off every stalked bud.

   Once I completed all the pruning, I used flagging tape to tie the shoot to my bamboo stake (photo at right). I also cut off the small piece of grafting tape that held the plastic bag tightly around the scion. I don't want any possibility of girdling such a fast growing graft.
   My final step was to replace the deer cage over the graft to prevent browsing injury.

Friday, June 26, 2015

Shaping a young tree with summer pruning

      This month I revisited a young tree I had pruned during the dormant season (photo at right). I was very interested to see how the tree reacted to my earlier pruning cuts and just where and how the new branch growth would develop in the spring.
   Here's a photo (at left) of the same tree--after pruning in March and once the tree has grown new shoots and leaves in June.  When I first pruned this tree, the only lateral branches that had good wide-angled branches attachments were in an area right above the graft union (near the blue tape). Above that, I had 3 1/2 feet of clear central leader. This is definitely not an ideal situation. This tree needs lateral branches to help balance the tree and promote trunk diameter growth.
   As you can see, the short lateral branches I left on the lower portion of the tree burst forth grew over two feet in length. At the top of the tree, I still have a central leader but several strong lateral branches have developed just below. These are growing rapidly and are starting to compete with the leader for sunlight. In the middle portion of the main trunk, I have some lateral branches forming but they growing with less vigor. To shape this tree further, I made several summer pruning cuts to help direct the trees growth into the summer.

    I started by working on the bottom of the tree (photo at right). The yellow arrow points to a rapidly growing shoot that originated with one of the short laterals left during the dormant pruning process. To prevent this shoot from overtaking and shading out weaker shoots above, I cut the shoot back to an outward-facing bud. 
   The red arrow points to a shoot that originated from a bud on the main trunk. This shoot has grown nearly two feet in length, so I decided to pinch out the terminal and force the branch to pause it's extension growth, mature remaining leaves, and build shoot diameter.
   These were not the only lateral branches I pruned. I made similar cuts to lateral shoots around the entire tree.

   At the top of the tree, I followed the 2-foot rule and pruned the terminals of lateral branches below the central leader. I also spent some time to remove all the stalked buds I found growing in each leaf axil on the central leader. Red arrows in the photo at left point to several of these stalked buds and the comparison photo shows the central leader after all the buds have been removed.

   The photo at right shows the entire tree after summer pruning. This tree illustrates key principles of directive summer pruning: Encourage the growth of a central leader, promote lateral limb formation, but keep lateral extension growth in check.

Tuesday, June 23, 2015

Topworking a large pecan tree: Graft aftercare

    Last month, I showed you how I went about top-working a fairly large pecan tree. Using a hydradulic lift, I placed bark grafts on nine major limbs throughout the tree's canopy. Today, I went back to the tree and found that all nine grafts had been successful but they were buried in a profusion of brushy growth (photo at right).  Three bamboo stakes, attached at the top of the tree during grafting, were the only visible clue that I had grafted this tree 7 weeks ago.
    I moved the hydraulic lift up to the tree and immediately started trimming off all trunk sprouts below each graft. It wasn't long until I had the ground littered with green pecan shoots. Once I could see the scions, I found that each scion had at least two shoots growing from the original scion stick (photo at left). Many of the new scion shoots had already grown 18 inches in length so I decided to replace my short bird perches with longer bamboo stakes.
   Once the bamboo stake was firmly taped to the tree, I trimmed the scion down to one shoot (photo at right). I then tied that single shoot to the bamboo stake using engineer's flagging tape. I also used my knife to cut off the green grafting tape that holds the plastic bag around the scion. These grafts are growing extremely fast and I don't want the tape to girdle the scion.
   I repeated this process for all nine grafts I had made on this tree.
    Once I finished all necessary pruning and training, I moved the hydraulic lift back away from the tree to see the results of my handiwork.  In the photo at left, you can clearly see some of the grafts I made and the bamboo poles that support those grafts. If you compare this photo to the one at the top of this post, you can also see just how many trunk sprouts I had to remove.  I have left several small side limbs on this tree to provide shade for the trunk to prevent sun-scald.
     I'll need to return to this tree in 4-6 weeks. By that time, more trunk sprouts will appear and the grafts will need addition ties to the stakes. I surely don't want to lose any of these grafts to breakage in a wind storm.