Monday, July 21, 2014

Mid-summer maintenance of a top-worked tree

     I've had some outstanding growth on my new grafts this summer and it was time for a little mid-summer tree maintenance. In the photo at right, you can see that the scion has outgrown the bamboo bird-perch that I attached during the grafting process. From this distance, it looks like the new graft is developing into a strong central-leader tree but a closer look reveals the need for some additional summer pruning.
    Even though I trimmed off all the stump sprouts back in June, new sprouts have appeared (photo at left). It is amazing to see green shoots literally pop out of the side of the trunk in such a short time. But like I did back in June, I cut off all new trunk sprouts using my pruning shears.
    Next I inspected the top of the scion.Wow, look at all those stalked buds growing at each leaf axil. If I allow shoots to develop from all these stalked buds, I'll end up with a bushy topped tree and no central leader. It a good thing I brought along a step ladder because I needed it to reach the top of the tree and carefully prune out all these unwanted shoots.
    With all my summer pruning efforts focused on pushing the tree to develop a dominate central leader, I knew it was time to replace the bamboo bird-perch with a more substantial tree-training stake (photo at left). I made my stakes by ripping a 10-foot-long 2 x 4 into 4 stakes measuring 3/4 inch by 1.5 inch (remember a 2 x 4 has the actual dimensions of 1.5 X 3.5 inches).  I attached the stake to the tree using electrical tape (duct tape would also work). I then tied the scion to the stake using 8 mil thick green plastic tape (1 inch wide).
    Judging from the rate of growth I'm seeing so far, this graft union should be completely grown over by the end of next summer (2015). The stake I attached this summer should serve to protect the scion from wind breakage until that time.
   While removing the bamboo bird-perch, I also removed the plastic bag and foil covering the graft union (photo at right). In the past, I've had problems with insects  tunneling in the wood under the wraps and slowing the healing process.
    When I removed the wraps, the bark was almost dripping with moisture. All that moisture can accelerate wood decay at the stock's cut surface so I decided to let the graft union dry out. However, the sudden exposure of the graft union to full sun can cause a sunburn that damages the tree's cambium.  To protect the graft union, I'll use white latex house paint as a sun block.
    I allowed the graft union to dry off while I attached the new tree stake and pruned the central leader (described above). Next, I grabbed a paint brush and painted the graft union (photo at left). Don't be afraid to slap it on thick. Remember the paint's role is to block out the sun and reflect the heat.

Use water-based latex paint only!!  I use exterior flat white.

     When I paint a graft union, I make sure to cover the entire area the was once covered by foil and plastic. This includes the top the stock and the lower portion of the scion (photo at right). The white paint also serves as a visual reminder of which trees have been grafted and the location of the graft union.

   If you would like to go back in time to see how I've top-worked and trained this tree, check out these posts;

1. Changing pecan cultivars by top-working

2. Forcing a bark graft