"...Fertilizing is fairly strait forward, but renovating old neglected trees can be difficult...
...As far as fertilizing goes, since the trees are not likely to be cared for regularly it wouldn't hurt to get a soil test from around a tree that is growing in similar soil conditions as most of the other trees are growing in just to be sure there is nothing the trees need. It's cheap and could help ensure the trees are in the best possible shape to be able to fight off disease. If they do get a soil test it may say to add Boron every few years, but other than that it would probably just be the standard N-P-K, but usually with older trees all you need for fertilized is nitrogen.
The best type of nitrogen to use is either ammonium nitrate (34-0-0) or calcium ammonium nitrate (27-0-0) If they want to use a blended fertilizer (like 10-10-10) then they can call around (a co-op would likely be the best place) to find someone that has fertilizer that uses ammonium nitrate as the N source. If they had to they could use urea (46-0-0), but it's not the best option because you can lose some of it through “volatilization”. It can literally evaporate into the air. If they have to use Urea, it's best to spread it just before a heavy rain and preferably right before a rainy week. Ideally the best time to fertilize is about a week before the last frost date for their area and to try to get it done as close to that date as they can (but no sooner), because if they wait to long the burst of soft tender new growth may not harden off in time for winter and could be killed. About five weeks after that date is as far as I would go, but 2-3 weeks would be much better. This only applies to using nitrogen. P & K can be put on any time if needed.
A general guideline for a normal full size tree is four cups of ammonium nitrate per tree for trees six to eight years old and six cups for trees nine years old and older. It should be broadcast under the tree, but kept six inches or more away from the trunk. Make sure they know not to just dump a large amount of nitrogen in a small area or they might end up burning the roots.
However, the best rout to go is to use shoot growth to decide if you need to reduce or add fertilizer the following season. The right amount of growth should be about 12 to 18 inches a year. If it grows more than that, use less fertilizer next year. If it grows less, use a little more fertilizer the next year. If they have to do some major pruning, and they probably will at first, then they should skip fertilizing that year (unless it's an old tree that's almost dead). The reason for this is there will be a whole tree worth of energy stored in the roots going back into a substantially smaller tree (not to mention a huge increase in energy from a lot more sunlight) so it's better to be on the safe side in regards to nitrogen because if the tree grows too much there is a risk of it getting Fire Blight which can kill it.
Since you mentioned there were some smaller trees you may want to treat them as semi-dwarfs. For Semi-dwarf trees eight years old and older, use four cups of ammonium nitrate per tree.
Also, instead off pruning a bunch of trees the first year they could just open the canopy so the tree's can get the sunlight they need, give them a half dose of nitrogen, cut out any dead or diseased wood and see what happens. Especially if they are not too keen on putting the work into trimming. Any apples that
develop would probably be smaller and not as sweet as they would be on a properly cared for tree, but they may be satisfied with the results. They could also prune just a couple trees to learn from and to see the difference it makes.
If there are a lot of weeds it's a good idea to spray some Round Up (or generic version) under the trees to kill the weeds so they aren't sucking up the nitrogen, water and other nutrients the tree could be using.
Pruning/Renovating neglected apple trees.
The most important thing to keep in mind is that the specific limbs you remove usually are not as important as the fact that they are removed to increase light penetration into the center portions of the tree.
The goal is to have at least 30% of the available daily sunlight come in contact with as much of the tree as possible. Start out by removing all the dead, diseased or crossing limbs that could rub each other. Also remove any limbs growing down, water sprouts and remove any limbs with sharp crotch angles since they break easily when under heavy loads of fruit or ice. It's best not to cut back more than 1/3 of the tree per year. Also, if you have to remove more than four large main branches, I would remove half of them one year and half the next year.
You also want to get rid of any mummified fruit while your at it.
As well as diseased wood like this Fire Blight Canker (bad stuff).
The best time to prune is late winter or early spring before the buds start to swell because that's when there will be the most energy stored in the roots. You will also avoid potential damage from sub zero temps and the bark is much less likely to tear so the wounds will heal quickly when the tree starts growing again. To help control disease and insects when you prune your cuts should be flush with the branch collar too or at least leave as small a stub as possible.
The two main pruning cuts to use are heading and thinning.
Heading cuts remove part of the branch and this causes buds below the cut to sprout and start growing into more branch's.
Heading can also be used to “head” a plant in a certain direction.
When heading back, cut just above a bud (about 3/8") so you don't damage the "root" of the bud. The bud you cut down to will become the new terminal bud.
If you cut too close to the bud it could die. Then the branch will die back to the next bud leaving a section of dead wood where disease and insects could set up shop. Cuts also shouldn't run horizontal, but at an angle so water doesn't set on the surface where it could cause rot and disease to set in.
Thinning cuts remove the entire branch. Very few if any buds will break below a thinning cut. This is the cut used the most for neglected trees. They will probably take over 90% of the wood using thinning cuts.
There are also two main types of tree structures to keep in mind, Open Center and Central Leader. Obviously you never know what you will run into in the woods and your not likely to get a perfect tree, but these pics help to get the concept across. Depending on what you have to work with they may have to create something a lot different than a central leader or open center design. You can get a good idea from these before and after pictures of what to do. This is an open center tree that was heavily pruned.
This pruned tree was about forty yards away from the tree in the photo above it. I used different trees because the pruned version of first one was a bad photo and hard to see. The before photo of the pruned pic was very similar to the before photo above it, but was actually a little worse. This tree was pruned hard so it was probably loaded with suckers the next year and probably didn't produce a decent crop of apples for a couple years.
I renovated a much older apple tree that was real screwy and I did about 60% of the damage they did in the above picture. It took about 6 years to produce again. Then it produced at least ten times the apples it had before. It probably would have produced in about half that time, but it was old, had to compete with a heavy sod and wasn't given any fertilizer.
Here is an open center that really isn't all that bad. Tons of suckers, but it has a good basic structure and looks like it might be able to be cleaned up in one year because most of it is small stuff so you wouldn't be removing a huge percentage of wood.
Central Leader
A Christmas tree shape is what you want for a central leader tree.
Ideally scaffolds (permanent main load bearing branch's) should be staggered like this drawing (ignore the numbers).
Here is a top view of a central leader that shows how the second tier of scaffolds are shorter and offset to help let in light to the lower scaffolds.
Ideally you want to remove all branches directly across from each other on the leader and space scaffolds uniformly around the leader to prevent crowding. It would be pruned into the shape of a Christmas tree and have a “light slot” of 2-3 feet (on a full size tree) left between each scaffold to allow light to penetrate into the lower branches and interior of the tree. Also any lateral branches that are weak and flimsy should be headed back 1/4 to 1/3 of their length to stiffen them.
However, with old neglected trees many times you have no choice but to get creative to get good sun and air flow into the tree because there may be no realistic way to get it to conform to either of the normal shapes. What you want to look for and keep are branches that are at a 45-60 degree angle from the central leader if possible. Because they are stronger, put less energy into vegetative growth and more into fruit production than more upright or horizontal branches do. This is due to how the mixture and levels of hormones change with the branch angle. I also like a nice wide crotch angle of 60-80 degrees where a scaffold meets the trunk, but anything from 45-90 degrees is fine. It will be too weak to be a scaffold if the crotch angle gets much less than that. Although I have seen people come up with some unique idea's to deal with a narrow crotch angle problem, like putting a post in the ground below the branch for support when the load gets too heavy or tying rope to the branch and then to the trunk at a higher point. I guess if there is a will there is a way when you need a certain branch.
There are also wound dressing's or pruning paints you can use where you cut, but the best thing you can do is make a properly placed good clean cut and let the tree heal naturally. When your done you shouldn't leave any pruned branches laying on the ground near the tree and don't burn them nearby either. This helps to control disease. Never knowingly leave diseased branches next to or under a tree. Completely remove them from the area.
Here is a good example of an overgrown tree that has been pruned back fairly hard. There is a little more pruning that needs to be done next year, especially on the left side, but it looks like they did a great job. I'm not sure if this was done over one or two years, but being a fairly young tree it should handle this amount of pruning well.
Before:
After:
It's sort of like hunting. If you understand the basic concepts your a lot more likely to get the results your after.
Here are some more examples that may help them.
"A six-year-old 'Delicious' tree (Left) before spreading, (Middle) after spreading, and (Right) after pruning. The weight of a crop will pull the scaffold branches down to form the conical tree shape. Note the removal of many limbs in the top half of the tree to allow light penetration."
Just in case they don't know what an apple spur looks like.
On the top of this one the central leader has been topped and three new sprouts have come up to compete to be the new leader. The one in the middle should be left and the other two removed with thinning cuts.
This one shows the difference between a leaf bud and a fruit spur with a fruit bud. Some trees bear on fruit spurs and some are tip bearers so they should look for spurs so they know which type of tree they are going to be working on.
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