Friday, May 1, 2015

Nature's grafting technique

    It has been a great week for grafting pecan trees. I've be grafting at the Pecan Experiment Field, grafting trees on my home farm, or showing folks how to graft during grafting schools. The other day I was grafting at my farm when I stopped for a minute to watch all the cars and trucks wiz by on US Hwy 166. Just think, all those people rushing back and forth--not one of them having the time or inclination to carefully carve out a scion and attach it to a sapling pecan tree. To me, grafting offers me the chance to slow down, enjoy the outdoors, and create a tree that will bear nuts every year for the next century (photo at right). I can't think of a better endeavor.
    During this week's grafting schools I visited several pecan farms. During one farm tour, I spotted a natural graft union that formed in a tree that had lost much of its canopy several years ago in an ice storm (photo at left). Once limbs were broken off by ice, the tree sprouted new shoots from remaining live branches with all new shoots growing straight up towards sunlight. As a result of this rapid regrowth, one limb crossed over another. At first, these two limbs just rubbed together in the wind, wearing a bare spot where the limbs touched. As the limbs grew in diameter the pressure against each other increased and the two limbs eventually formed a natural graft union.
   These kinds of natural graft unions are not that common in mature pecan tree canopies. But under the ground, the roots of adjacent trees frequently overlap each other and form natural graft unions. Root grafts are the main reason we do not recommend using tree killing herbicides to treat the stumps of pecan tree removed during a tree thinning operation. The herbicide might control the formation of stump sprouts from the removed tree but the herbicide might be transferred to an adjacent tree via a root graft causing unwanted tree injury.