Friday, March 9, 2007

Winter Pruning Overview

Winter pruning and training to achieve optimum tree structure is part science and part art. It's a very important part of having an orchard, a skill that's fun to learn and very satisfying to practice. Courses are given in many public gardens or arboretums. The County Master Gardener Programs will also have introductory and advanced courses. The L.A. County Urban Orchard Team can put on a workshop at any school or community orchard. Common Vision has online resources as well to make it even easier. We want to help you feel empowered and informed through this great activity. Feel free to contact Common Vision with any questions.

Winter is a good time to do very important "Maintenance" pruning, and you've probably already had some practice with the post-harvest pruning and trimming. When the trees are bare of leaves, the woody structure is more clearly visible, making pruning much easier. A primary objective of training and pruning is to develop a strong tree framework that will support fruit production. Improperly trained fruit trees generally have very upright branch angles, which result in serious limb breakage under a heavy fruit load. This significantly reduces the productivity of the tree and may greatly reduce tree life. Another goal of annual training and pruning is to remove dead, diseased, or broken limbs. Pruning is also really important to optimize fruit production, open the canopy for more light for flower bud development and optimal fruit set, flavor, and quality, as well as airflow for drying out and disease prevention.

Are you move of a video-based learner? Most of this is also covered in This Pruning Video

Have a Newsletter or Worksheet with you if it helps!

So first things first, a diagram of a tree and terminology:

eaf buds
d)short shoot
e)long shoot
t)terminal bud

Suggested Pruning Cuts

A. Suckers.
B. Stubs or broken branches.
C. Downw
ard-growng branches
D. Rubbing or criss-crossing branches
E. Shaded interior branches
F. Competing leaders
G. Narrow crotches
H. Whorls

It's important that you take a moment, and be sure that you can identify this year's growth from the previous year's growth.

So, we'll stop for a little exercise: Look at the end of this past Summer's growth. The shoot tip has a little bud on the end (that will be the start of growth this coming Summer). Run your finger back towards the trunk. The bark of the shoot is very smooth, quite green, or at least greenish brown. Soon you come to a little scar, a circumferential ridge. This is where last year's bud was. The bark now becomes somewhat rougher and browner; the shoot is a little thicker. You've now identified the transition to the previous year's growth. Actually, you can keep running your finger down and identify each year's successive growth. For fun, you can go right back to the trunk, and there you have the year your tree was planted!

Why is this important?
An apple tree will set its fruit on a little "Spur." Year after year the tree will produce fruit on the same little spur, maybe more than 10 years.
We don't want to cut this Spur, or its branch. A peach tree will set its fruit on the shoot that grew last Summer. Once it has produced a peach on that spot, it will never again produce a peach there ever! So, that's why the little exercise has practical value. We want to keep the older wood in the apple, but we continually need new wood on the peach tree...if we want peaches.
And remember the important rule: We don't prune the apricot in the Winter! Perhaps it's best to put a little sign on the apricot: "No Prune Zone", or perhaps Pruners in a circle with a line through them (the international No Prune sign ?).

PRUNING: Let's review the simple approach.

The following applies to all of the trees:
1) Prune out the Suckers. These are the very vigorously growing shoots, that come from the "Root-Stock" below the "Graft Union." Recall that's the slightly swollen area 2" to 6" above the soil level.

2) look for any Watersprouts that may have been overlooked in your Summer pruning. These are vigorous growing shoots, not usually bigger than the width of your little finger. The bark is smooth and green and they grow straight up, without any branches. They rarely bear any fruit, and they tend to shade more important fruit bearing branches. So...cut them off, right outside of the little branch bark-collar. Remember that's the little swollen ring of bark at the beginning of each branch...where it originates from the trunk. Or where a shoot originates from a branch. Protect the "Collar," because that's where the tree will heal the pruning wound.

3) Now that you have a good view of things, remove any branches that have broken, or are rubbing against other branches. Branches or shoots that are pointing down or towards the center of the tree (rather than growing up and outward) are very apt to cause trouble. They should also be the little "branch bark-collar" of course and make sure there are no stumps sticking out...nice cut!

4) Try to recognize any diseased shoots or branches. Fire Blight, for example, unfortunately affects pears and to a lesser extent apples. The end of the branch may look burned or blackened, bent over, and often with the dry crumpled leaves still attached. Obviously diseased areas like this should be pruned out, removing at least 12" of healthy looking branch together with the diseased section.

Whenever you're pruning branches that don't look perfectly normal be sure to disinfect your pruners between each cut with 70% to 91% Isopropyl alcohol (drug store alcohol). Dip your pruners for a few minutes after each cut. An old tooth brush or spray bottle is also helpful for this. Also make sure your pruners are sharp!

If your trees are 1 to 3 years old, or if they're growing slowly you can limit your pruning at this point.

This next part is for those trees that are more than four years old, and have grown substantial structure:
5) Last, but equally important, is to remove some of the previous year's growth. This will protect the tree from limb breakage and from fruit setting too far out on a fragile branch. This type of pruning will also lead to larger, better quality fruit.

Pruning a mature tree:
The peach and nectarine, (and the apricot, once the rainy season is over) need "heavy" pruning. 50% of the one-year old shoots should be removed, that would be every other 1-year-old. shoot...pruned! with the remaining one-year old shoots: get a good look at the whole shoot, and mentally divide it into thirds. Then remove the outermost third. So we've left a little more than 60% of 50% of the shoots. Who said there would be no math?

There's going to be a lot of wood on the ground!
Years ago my instructor said, "When pruning, or thinning fruit it's best not to look down!"

Now what about those 2-year old shoots, they're not going to bear any more fruit! Assuming that they are not needed as major branches, they should be cut back to a one-year old shoot, or near a nice bud where they can start some "new wood."

The apple and pear trees need a lot less pruning. If they have not yet reached your target size, remove only about 10% off the ends of this past Summer's growth (remember how to identify it). This will encourage branching and more fruit spur formation.

The pomegranate will have a lot of suckers coming from around the main trunk. Unless you want to grow the pomegranate as a "bush" (which is OK), prune these extra little trunks down to the single large one. These suckers are really accessory trunks, part of the main fruit producing tree.

The persimmon sets its fruit on the ends of last year's grows, so don't cut off too many of this "fruiting wood."

With all the trees; keep the tops pruned down so the trees do not exceed 8 feet in height. As we've mentioned before, this type of height pruning is best done during the Summer, when you're less likely to stimulate more rapid regrowth.

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