Grafting a frost injured tree

    In spite of a cooler than normal Spring, my pecan trees have started to re-bud following the April 21 frost. The photo at right show the terminal of a young pecan tree that is pushing out new green shoots from secondary buds just underneath frost-killed primary bud shoots. This was the signal I was waiting for to start grafting again.

   In choosing trees to graft, I select young trees that have made vigorous shoot growth the previous growing season. The tree pictured at left was about 6 feet tall and a perfect size for bark grafting. 

    When folks are just learning to graft pecan trees, they often wonder if there is a proper height to make the graft. When I graft, I choose the height based on two criteria. The diameter of the stock should be no larger than 3 inches in diameter and height should comfortable for making grafting cuts. On smaller trees, like the one pictured here, I'll cut off the stock at about 18 inches off the ground or at perfect height for me when sitting on my cooler to graft. On larger trees, I'll cut the stock at chest high to make grafting while standing more comfortable. Either way, I always remove at least 2/3 of the stock tree's height to force the tree to accept my graft.

    Once I choose the approximate location for cutting the stock, I carefully inspect the trunk for any a major knots or pruning wounds. On the tree I've selected to graft, I found two pruning wounds on either side of the trunk (photo at right). Underneath those wounds, the bark was nice and smooth, an excellent site for bark grafting.

    To make scion insertion under the bark easier, I cut the stock just below the two pruning wounds (photo at right).

    

    Once I prepare the stock by making a vertical incision in the bark, I turn to carving the scion. The photos at left show the cuts I make into the scion. The first cut is a deep cut to narrow the width of the scion to allow it to slip under the bark of the stock. Next, I make a shallow cut to expose the cambium on the back of the scion. This cut is made at an angle to deep cut. At a right angle to the deep cut I peel away a sliver of bark to expose cambium along the edge of the scion that will abut the verticle incision I made in the bark. My final cut is to carve a chisel point into the end of the scion to facilitate insertion under the bark. A detailed description of this grafting method can be found HERE.

  

  Once the scion is prepared I can quickly insert it into the stock and staple it into place. First, I place a row of staples up the incision of the bark. These are places at an angle so both sides of the staple sit firmly against the bark. Then I place a verticle row of staples just to the left of the scion to press the stock's bark up firmly against the shallow cut I made on the backside of the scion.

 

   To complete the grafting process, I wrapped the graft union in aluminum foil then covered that wrap with a plastric bag tied both on the scion and the stock (using green tape). I placed a drop of white glue on top of the scion to seal in moisture then attached a bamboo stake to the tree with electrical tape to prevent bird damage and provide support for the growing scion. My final step was to label the graft with an aluminum tag imprinted with the cultivar name.

     When completed, my grafted tree looks tiny compared to the stock tree I started with. In the photo at right, I layed the severed top of the tree next to the graft to give you an idea of how much I pruned off.  This may look like drastic surgery but when this graft takes, the new shoots will grow rapidly attemping to replace all that wood I pruned off. In addition, a fast growing tree is easier to train to central leader.