Allen said that his grandfather always would say you want to be able to throw a hat clear through the tree. I take this to mean bare is good. Cut those limbs off, baby!
In our area (NE Ohio) we prune anytime between January and March.
I should start by telling you that we have an old orchard. Some trees are estimated to be 10-15 years old, and others 20+ years old. When we purchased our property, the trees hadn't been pruned/tended to for at least 5 years - at least! They were kind of a mess. And in that time, some limbs had grown from suckers to full fledged fruit bearing limbs. A lot of our trees are not trimmed in 'normal fashion'. This could be a good thing, or a bad thing. Depends on how you look at it.
In this photo below, this is kinda of the idea on ideally, how you want your tree to be formed.
You want your large, main 'branch', which is called the Central Leader. This is the branch at the foundation of your tree that runs from ground to top.
From your central leader, you then want Levels. Depending on your tree and the size, you want probably about 3 levels on average. As I mentioned before, most of our trees aren't average due to the years they went without maintenance. If you go to an orchard that has maintained their trees from the start, you will see what I mean. If you can tell in this photo, the pink arrows point out the first level of brances, the yellow the second level of branches. You don't want the level above to shawdow out the level below - they need to receive even amounts of sun. Think of it as a compass - if level one has branches facing North & South, then you want Level 2's branches to face West & East - makes sense?
You will also see the 'odd limb'. This was most likely a sucker that grew into a full sized limb during the time this orchard wasn't tended to. When we came in and started putting it back into production, we had some mentoring for an 'apple expert'. He took HUGE cuts - like chainsaw sized cuts - to all the trees in multiples. So, this one could probably go now and just didn't go then because of the sheer amount of other limbs that most likely went in its place!
Don't be afraid of 'big cuts'. One year, or two, you might leave a branch and by the third of fourth year, decide it doesn't need to be there - so cut it! Less is more with the trees. Too many limbs and you are taking away from the quality of apple that will grow. Many limbs = many [smaller] apples. Think quality versus quantity.
This photo below shows a tree that looks rather bare - and it is! It was just pruned. You will also notice this tree doesn't really have a central leader. It has multiple smaller branches so we make do with what is has.
Below is the same tree as above, pruned, with an unpruned tree pictured in the right - 'Tree #2'. Can you see the difference between the pruned and unpruned tree?
Below is another tree already pruned. Again, no central leader on this one, but you can see the tree seems bare. No excess of suckers.
Speaking of suckers...
Below this is actuall a Quince tree and these are nortorious [at least in our orchard] for sprouting all kinds of suckers at the base every year. GET RID OF THOSE BAD BOYS!! If you garden, they make great trellis material! When they are at the base level, you can carefully take a chain saw to them if you prefer.
Below is a photo of one of the aisle in the orchard - pre-pruning. Once they are all pruned, I will take the same shot again. It will be a fe weeks though. These are some of the tougher trees in the orchard due to their massive size and suckers. We save the best for last!
This is really just a dip into fruit pruning territory and there is so much more we could disucss. These are the basic though that should help you out to start. Please feel free to ask more questions and we are happy to help you out any way we can.
Tami asks: I have 3 apples trees and 1 peach that are only a few years old. Two are going into their 3 year and I hope to prune this weekend. Any tips to offer? It's good to see that you don't have to allow the tree to get HUGE to bear fruit. I'd like to keep them reasonable size wise.
ANSWER: Tami, hubby says that since your trees are younger, you really don't need to [most likely] trim a lot. What you want to do is choose suckers (not at the base, but within the tree) that you can coach to become real limbs. You will want to bend them out and under another branch to help them form a paralell stance. If you don't have other limbs to tuck it under yet, you can tie a piece of string to the end of it with a small weight of some sort (nut, bolt or something of the nature can do the trick) to help coach the limb to grow paralell to the ground. My mom has young trees...I will see if I can take some pictures later in the week for you to give you an idea with a younger tree.
Roberta asks: I know nada about trees, esp fruit bearing ones. I take it you do not want those multiple tall thin growths on the trees - do they take away nutrients for the apples?
ANSWER: Roberta, yes. You want some, but as your tree grows and matures, less is more. Otherwise you will have a tree full of branches competing with each other.
Golden Oldies Farm asks: Do you recommend any books on orcharding?
ANSWER: One book we liked that keep things fairly simple was 'Backyard Fruit Production' by David Schlabach, but otherwise, our local extension office provided the best info along with a few fruit tree pruning clinics we attended at other area orchards. Look into larger orchards in your area to see if they offer any.