Tuesday, April 19, 2016

When is it time to graft pecan trees?

    We have a small planting of seedling pecan trees that I plan on grafting this spring. All the trees in this planting are open-pollinated Kanza seedlings. This morning, I looked over the field and noticed that some trees in the planting had entered the leaf burst stage (photo at right).  Since I'll be using a bark graft to establish selections from our breeding project in this field, seeing trees in the leaf burst stage has made me anxious to start carving scions and placing grafts.  You see, leaf burst is the signal I use to determine when the bark of the tree will slip enough to allow scion insertion.
     However, looking across the entire field I noticed that bud development varied widely among seedling rootstock trees. Right next to a tree in leaf burst, I found a tree in the bud enlargement phase of bud development (photo at left). If I tried to place a bark graft on this tree, I'd probably find that the bark on the main trunk would not slip and I would have trouble inserting a scion. A tree at this stage of bud development is just not ready for bark grafting.
    Moving down the row of seedling trees I found several trees in the inner-scale split stage of bud development (photo at right). If I was planning to use a three-flap graft, this would be the perfect stage of bud development to start grafting. However, the trees in this block have all grown much too large in size to effectively use a three-flap graft. Since the bark graft is the preferred method to use on trees with trucks that range from 1 to 4 inches in diameter, I will need to wait a little longer before attempting a bark graft on the tree pictured at right.  
     Even though a handful of trees in this block of Kanza seedlings have leafed out far enough for effective bark grafting, I'll probably wait another week before grafting. This will allow the other trees in the planting to catch up in terms of bud development and allow me to graft every tree in every row all in a single day. That way I'll be sure to get every tree grafted and grafted to the right breeding project selection.