Thursday, March 2, 2017

Reading the Landscape: Apple trees

If you are addicted to reading the landscape you can easily pick out the apple trees due to their distinctive form.

But what causes that form?

The following is a short, primitive exposition on why apple trees look the way they do.  And, by extension, why apple trees must be pruned to be profitable.

Tree A is a virgin on the brink of production.  Tree B shows one branch of this tree with a fruit load.  The dashed line shows the original position of the limb before the weight of the fruit pulled it down.
Tree C is the same as Tree B but later in the season as the fruit sizes up. You can see a "sucker" starting at the point of inflection.
The current thinking is that branches and the growing tips produce growth regulators that suppress buds breaking into growth. Sunlight destroys that growth regulator and the buds are free to grow.  That is why suckers pop up at the point-of-inflection, it is the most exposed to sunlight.

Fruit sets on both branches the next year.  (F) The lower branch is shaded and produces smaller, greener apples with less sugar.  The weight of the fruit starts to pull the upper branch (formerly a sucker) down as well.
The branch looks like this after five or ten years.  It goes into alternate bearing as one year it sets way too much fruit.  Keep in mind that this is just one branch.  The tree might have twenty such branches and they are growing in three dimensions.
The buds "decide" whether they will be vegetative or fruiting based on the carbohydrate status of the branch.  Setting too much fruit results in low carbohydrates.  Fruit are carbohydrate sinks.  So the next year there is no fruit.  Then too much fruit....

Without pruning the tree produces no fruit one year followed by vast amounts of runty, sour, green apples the next.  Neither condition is rewarded in the market place.

A typical pruner would remove the outer portion of the limb just outboard of the branch with the red apples.  Then he would remove half of the length of the branch with the red apples, right at the point of inflection.

If he did that to the entire tree the shortened horizontal limbs would throw more suckers due to the higher light levels inside the canopy.

The following pruning season the pruner has the option of making the tree even skinnier as he will have more fruitful branches to choose between.
It is worth noting that apple trees that remain open even when not pruned are not producing very much fruit.  If the dense, layered look is due to the effects of many years of heavy fruit production...then thinking in reverse, uncared for trees that do not have that look are slackers.

I tried to take photos to show this phenomena but they were always too busy.  I could see the layering and yearly accretions of branches, but that is because I could walk around the tree and see it in three dimensions.  I found it impossible to capture that in 2-D photos.

However, simple pencil sketches, even though they are primitive, can clearly illustrate the phenomena because there is absolutely no spurious detail to obscure the point.
640-by-480 and 0.3 megapixels.  Image from HERE
This point, that sometimes less is more, is completely lost on people who are in an arms race for the most megapixels on their smart phones.  A muddled thinker with a 20 megapixel photo is no clearer than if he had a clearly focused 640-by-480 photo.  And sometimes even  the 640 X 480 photo is too much.

1 comment:

  1. Very interesting. I didn't know that.

    This was very interesting, too.