Tree Growth and Pruning
                            by Jim Blackburn 
 

Back east as a kid I noticed sometimes farmers would drastically bend and tie a young tree to form a seat in the orchard. In the figure, notice at Item 1 that as the tree grew the "seat" never got higher - only bigger around and stronger. Trees, like most plants, grow at their tips. They get bigger around (as evidenced by growth rings) to support the top growth, but a branch of a growing tree never gets higher. That bend on a young tree is still the same height in old age. So if you want a fork in your young sapling about so high up, prune the young tree to the point where you want that fork later. That bend or fork isn't going to rise as the tree grows.

When I am pruning my trees I make sure I can walk under them if there's a path below. I am about six feet tall so I take out the lower limbs so I can walk underneath without scrunching down. Interestingly, as noted at Item 2 in the figure, each year I find there is a next higher branch hanging down, and so I prune that one too. You would think that trees are growing upward and if you trim off those low hanging ones that would be the last of it. Not so.

Trees grow at the tips and the trunks get bigger around but the lower branches, wouldn't you know, dip downward! Prune off the low fellows so you can walk under them and the next year there is the next branch dipping down to interfere.

My botanist friend, Steve Jones, tells me this is natural. While trees basically grow taller, each branch grows out to receive the best sunlight and the lower branches, seeing an opening where I cut out branches last year, can now bend downward to get a better helping of sunlight.

I also prune a few interior branches as the books suggest, such as those which cross over each other or are rubbing on one another, as in Item 3 of the figure.

Did you know Palo Verde will also prune themselves? They will let a limb die when they haven't enough water available to support all the foliage. On the trees close to the house I prune out these dead branches to prevent any fire from easily spreading. Further from the house I leave them alone because it's their nature and besides they provide good shade for animals.

About twenty feet away from the deck at my home there are several Palo Verde trees that nicely block the view of my neighbors and their lights at night, but allow me to see over them north to Elephant Butte, Skull Mesa, Sugarloaf, Go John and Black Mountain. Now they are growing high enough to obscure the skyline a bit, as in Item 4 of the figure. I don't want to shave the tops like the electric company does to trees under their power lines. My landscaping friends suggest just pruning a few shoots down a foot or so to the next lower joint, thinning a little. Pruning down to a junction doesn't leave a thick dead end showing. I leave a few branches sticking up but can see through them in a natural way to the beautiful distant horizon.

So I've got an ongoing pruning task. I am told I can prune a little anytime of the year but major pruning should be in January or February and never more than a third of the growth. And when I trim the low hangers for my path underneath or for my car to drive under, the next lower branches are going to droop down. The forks in trees don't grow higher, but the ends continue to grow and the lower branches really do bend down and outward to capture a little more sunlight and scrape my head and my car - a continuing pruning chore.