While I'm out grafting trees, I often pause at trees that I've grafted in past years to give them a little
directive pruning to ensure that I maintain a central leader on rapidly growing grafts. The photo at right shows a tree that I grafted last year. I had 5 feet of new growth from the scion last summer and I developed a nice straight trunk. This year at budbreak, the very top of the tree exploded with dozens of new shoots all clustered at the very top of the tree. Left to grow unchecked, these news shoots would form a "crows foot" at the top of the tree and I would loose my central leader. A few snips with my pruning shears and I can
direct all the tree's energy into growing a new central leader while at the same time encouraging lateral branching further down the stem. Let's take a look.
My first step was to look over the very top of the tree (photo at left). I had new shoots growing every-which-way. At each bud node, the primary, secondary, and tertiary buds had broken and were developing into new shoots.
As I looked down the stem, I passed over nearly 3 feet of dormant buds before finding a few buds breaking to form lateral branches (photo at right). This is how apical dominance works in pecan. The very top of last year's growth gets the greatest push for new growth. That growth, in turn, inhibits the growth of buds below the terminal via hormonal signals. When the hormonal signal weakens with distance this allows buds to break further away from the terminal. My goal in directive pruning is to reduce the negative effects of apical dominance on tree form and encourage both a central leader and the development of lateral branches.
My first pruning cut was made at the very top of the tree. The terminal of this tree had at least 6 new shoots growing in tight competition. With a single cut, I began the process of isolating and developing a new central leader (photos above).
To reduce the competition from shoots just below the new leader, I used my clippers to totally remove those shoots from the tree. (photo at left).
By pruning the new growth at the top of the tree, I was directing all the tree's energy into my chosen central leader. However, my work was not quite done.
I still had 3 shoots growing at the very top of the tree. With careful pruning I removed the shoots growing from the secondary and tertiary buds while leaving the shoot growing from the primary bud (photo above).
When I finished pruning, my young tree looked sparser but I now had a single growing point at the top of the tree. And I know from past experience, that thinning out top growth stimulates the breaking of lateral buds to form the lateral shoots needed to fill out the canopy of the tree.
I don't confine this directive pruning technique to just one-year-old grafts. The tree pictured at left was grafted 2 years ago and could also benefit from some directive pruning. To give you an idea of scale, the step ladder in the photo is four feet tall. I'll need that ladder to reach the top of the tree to make a few directive pruning cuts.
Note that the central leader of this tree has no lateral branches for almost 4 feet below that little ball of spring growth at the top of the tree. Below that, the tree has developed a good framework of lateral branches. New spring growth on each lateral branch mimics what we see at the very top if the tree. New shoots are only growing from the apex of each lateral shoot.Here's how I pruned this tree.
First, let's look the bud break from lateral shoots (photo at right). Proliferation of new shoots on the terminal of lateral shoots is a good thing. This will create an even greater leaf area for the tree to capture solar energy. However, I pay attention to the direction the new shoots are growing. I remove any new shoots that grow strongly upwards towards the central leader.
Once I inspected the lateral shoots, I climbed up the ladder to address the new growth at the very top of the tree. Just like the tree in my last example, the very top of the tree is a jumble of new shoots with every new shoot competing for light. I pruned the top of this tree exactly like I did on the one-year-old graft discussed earlier (photos at left).
Pruning trees early in the season is one of the most important techniques for developing a well structured tree (photo at right). My goal is to make sure each tree in my grove develops single strong trunk. At the rate these trees are growing, it won't be too long before directive pruning the central leader will be out of my reach (I limit myself to using an 8 foot ladder). Once a tree grows too tall, I let the tree grow naturally. My only pruning at that point is to remove lower limbs to make working under the trees easier.
Once I inspected the lateral shoots, I climbed up the ladder to address the new growth at the very top of the tree. Just like the tree in my last example, the very top of the tree is a jumble of new shoots with every new shoot competing for light. I pruned the top of this tree exactly like I did on the one-year-old graft discussed earlier (photos at left). 
