My ramblings about pruning fruit trees....

I was taught about pruning in a course I took at Cal Poly San Luis Obispo, back in 1987. The class was taught by two professors -- who had been the head horticulturalists at Disneyland. They taught that every time you pruned a plant you wounded it -- the exposed end of the cut off branch would begin to die. This death would continue into the plant until the plant was able to grow a protective layer of bark over the exposed interior surface and "compartmentalize" the dead wood inside the plant.

They argued that a large branch, pruned in the middle ("Pollarding" an old tree) -- produces a large dead area at the end of the branch. It responds with rampant new growth in the thin live wood surrounding the dead center. These branches were considered weak because they weren't believed to be anchored to much live wood (However people "top work" old trees with "cleft grafts"?) My professors argued that it was better to cut an entire branch off -- clean at the trunk -- than out in the middle, like "incorrect" pollarding. They said that if you wanted to pollard, start "pollarding" while branches are small.



At Cal Poly, if I remember correctly, we were taught to prune "through" the "growth centers" at the base of the branch. This thickened portion of bark at the base of the branch was thought to be the area where the new bark would be produced -- that would compartmentalize the dead wood. By pruning as close to this "growth center" as possible -- OR EVEN RIGHT THROUGH THE MIDDLE OF IT -- the growth center could compartmentalize the dead wood fast. Wound paints were used as temporary "bark".

A different theory is now popular. The "growth center" is now called a "branch collar". Lee Reich writes:

"Cut the branch just beyond a line from that ridge to that collar. That ridge and that collar will form a natural protection zone, preventing the spread of infection into the trunk when the branch is removed. Removing or damaging the protective zone also can cause sprouts to grow in the vicinity of the wound -- just what you don't want when you make a thinning cut!"

The idea of a "protective zone" is new to me. Lee argues against using any sort of wound paint. "Such dressings, for the most part, keep the wound moist, maintaining a hospitable environment for disease-causing microorganisms."



When I moved up to Davis, from San Luis Obispo, I found that UC Davis advocated much less severe pruning than they taught at Cal Poly. The plants do tend to produce more fruit when they are pruned less, but at Cal Poly they argued you should prune more severely to limit disease -- particularly mildew which overwinters in second year wood -- and keep the trees a little more manageable, since we don't have as much room as they do up in the Central Valley. And the Central Valley is drier and they don't have to worry about mildew, like we do on the coast.

Plants grow vigorously in response to the pruning so.. pruning more severely -- requires more pruning . If you "top" a tree you redirect its energy away from its heighest point.. If you shorten a branch you redirect the energy (More side shoots). And the tree can become too "bushy" if you don't prune these. Believe me, I am very experienced at pruning fruit trees wrong!

I'm supposed to be talking about pruning fruit trees, and I've been rambling about pruning in general... Well you'd be amazed at how many books I've read about fruit tree pruning that seem to only focus on pruning the trees in the Fall or Spring for structure. You know... wide branch angles.. space around the tree.. not crossing... central leader.. open center.. espalier.. etc.. etc... Okay.. so I get a nice looking tree.. but sometimes it doesn't seem to produce any fruit....

Then I read what Lee Reich wrote about Louis Lorette's system of espaliering apples and pears, developed way back in the 19th century, in France. His system starts in the spring AFTER the main stucture has already been established -- AFTER "arms" (my words) have been chosen and "trained" sideways. The "first" pruning is done when the side shoots, on the arms, are about two inches long. This is a pruning of the arm. If the "arm" hasn't obtained its full length yet, you are supposed to cut back the previous season's growth by one-quarter to one-half. Then.... when the side shoots become woody, one-quarter inch thick, and about a foot long -- you are supposed to cut them all of the way back to the whorl of leaves at their bases, leaving a puny stub about one-quarter of an inch long. THIS PROMOTES THE FORMATION OF "SPURS" ALONG THE ARMS!

The other systems of espaliering fruit trees have grown out of this system -- and even the methods of summer pruning fruit trees (Or "fruit bushes" as the British call them) seem to have.

Cherries, plums, apricots, andf other fruit are espaliered as "fans" (Maybe somebody can explain to me why). but these "fans" are pruned similar to the apples and pears -- except the side shoots are summer pruned back to six inches, to produce "spurs", rather than the quarter of an inch like the apples and pears...

And I've got a little book from "The Royal Horticultural Society"! called "Growing Fruit" that describes year-round pruning methods for fruit "bushes" (Little trees). The Fall, Winter, Spring pruning is for structure -- just like the espalier but in a different shape. And the summer pruning (July-August) seems to be focused on the same sort of pruning for the espaliers -- focusing on creating "spurs" along the stems. The size control (topping) is practiced each May.

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Any thoughts? Disagreements? Arguments for or against my brilliant pruning overview? (In my defense I'm an enthusiast and not an expert by any means).


Richard Primbs
Encinitas CA

And to confuse matters a little more some of the apples prefer to bear most of their fruit on the tips of branches rather than on spurs. Fuji is a "tip bearer". So obviously "tip bearers" must be pruned differently from spur types.

I have a plum tree which has been cut way back because we had to remove something from the backyard and needed the space. Now that it is 60% of it's original shape how should I simply prune it, if at all? Do you think that we'll get any fruit this year because of the severe pruning?

Roz,

I'm still learning but I'll volunteer some suggestions anyway..

Do you know what type of plum it is? Is it a Japanese plum or a European plum? (The Japanese plums are more vigorous). Our plum is a "Beauty" (Japanese), with a "Santa Rosa" (Japanese) grafted onto it.

Has your plum been pruned with a "central leader"? Or with an open center? Could you post a picture? Basically the branches that grow horizontally bear the most fruit. So you might want to remove vertical shoots that don't have spurs

I'm assuming that you "headed" the plum back (Shortened the main branches back to a good branch -- or the main trunk). That should stimulate the plum to put out more growth along each branch.

For summer pruning (Late June to late July) you can pinch out the growing points on side shoots when they have five to seven leaves -- to stimulate "spur" production. And you can shorten branches to the length you want.

As you can see, it has been pruned heavily because we needed to get something out of the backyard. It is usually about as big from side to side as it is tall. It has very dark purplish plums usually about 2" in diameter and they are ready for picking the second or third week in June. I really don't know what kind it is, or if we'll get any fruit this year (how will I reach it?)Grateful for any help...Roz

Here's the photo (I hope) I had to shrink it...Roz