Time to think about tree thinning

   Over the past several years, I have outlined our plan for thinning a block of Kanza trees.  Early on, we recognized that the trees in this block were not all growing at the same rate. Portions of the orchard started to crowd faster than other areas as the trees responded to soil variation within this 3 acre tract of land. We devised a total orchard thinning plan but we have been removing trees only when adjacent trees start to crowd.
    Yesterday, as the sun was shinning and the temperatures reached a balmy 32 degrees F, I walked through the Kanza block to get a feel for which areas would require thinning this winter (photo at right).  Just walking through the orchard its sometimes hard to visualize which sections will require thinning next.

    One method I've used to help plan my next thinning cuts is to plot out the trunk diameters of every tree in the orchard (figure at left). In the figure, each tree in the orchard is portrayed by a green circle that graphically represents trunk diameter as measured after leaf drop in 2014.  All the blank spots on the map are the locations where trees were removed previously.
    Using the map as a guide, I go out to the orchard to visually determine which trees actually need to be removed. I'll stand between two adjacent trees and look up. If the branches are close to touching its time to thin. Let me show you what I mean. 
    On the map at left, I have placed a red box around adjacent trees at two locations in the orchard. At each location, I laid down on the ground between the two trees and took a wide-angle photo straight up. Tree 6-10 is 10.3 inches in diameter while tree 7-10 is 11.0 inches. Just a couple of trees to the south, tree 6-12 has a DBH of  9.2 inches and tree 7-12 is 8.3 inches in diameter. From the map it looks like trees 6-10 and 7-10 are almost touching while trees 6-12 and 7-12  still have some room to grow. Now lets look at the photos.

    The photo at right shows how close the canopies of trees 6-10 and 7-10 are to each other.  The dormant stems of each tree are not touching each other yet but add another summer of stem growth and a full load of leaves and you would see a closed canopy during the summer of 2015. I'll be thinning some trees out of this area of the orchard.

    Moving down the row to trees 6-12 and 7-12, the photo reveals that there is still plenty of space between these two trees (photo at right). In this case, I won't need to thin trees in this portion of the orchard for a year or two.
    We have been thinning this orchard a little bit at a time since 2012. In that time, I've come to realize that our Kanza trees start to crowd when trunk diameters of adjacent trees both exceed 10 inches. However, you must remember thinning decisions should be based soley on your particular soil type, initial tree spacing, and cultivar. We started this Kanza block at a close tree spacing of 30 feet x 30 feet. The closer the initial tree spacing, the smaller the  diameter the trees will be when thinning becomes necessary.