Are these seedlings in pots? If they are outside, make sure they weren't planted too deeply. There is a line between the 'root ball' of the tree and where the bark begins. Any soil, bark chips, mulch, rocks that covers this bark will eventually kill the tree. Bacteria eat at the bark if moist and just under the bark (scrape your fingernail and you will see bright green...) is the vascular system of the plant. It is very thin and once this is compromised the tree will die.
Make sure that there is always a circle of bare soil/mulch around the base of the tree that is as wide as the root ball in this case and later as wide as the 'drip line'...if your tree were an umbrella the drip line is where the rain falls off the umbrella and onto the ground. The drip line can stay 4-5' in diameter once the tree is established enough to compete with a bit of lawn or plants.
Do not over-fertilize or under fertilize. Either learn the symptoms of nutrient deficiency and excess or get a soil test done by your county extension service. Or both. Slow release or organic fertilizers are best.
As for pruning, yes, you can prune damaged branches, crossing branches and branches that angle towards the center of the scaffold of your tree. Tiny branches that have very small diameters compared to the trunk of the tree (or main branches) from which it grows should be pruned. The difference in diameter means that the leaves on the little diameter branches are not situated properly in relation to light to produce enough or efficiently for the tree. The tree in turn is not supporting those branches and they will die naturally. In this way you are helping the tree by cutting off non-productive branches and the energy that branch used albeit small is now being diverted to more productive branches.
Leave the leaves alone. If they come off with branches, fine. Leave the tips of the branches alone. Pruning the tips of branches is called 'heading' and is used if you want dense shrubs. Tree species have identifying shapes...to change this shape by heading, pollarding should be left to professionals and those that like to create a high-maintenance tree.
Something to remember; when you have a branch on a tree it is AT the height it will always be...and as the diameter grows, it actually is lowered. Don't worry about any major pruning until the tree is the height you need it to be. Now it is all about optimum health and growing.
At the end of a branch, the terminal bud, is where most of the energy in that whole branch resides. We are talking about any branch. When that bud gets removed all that energy is then diverted to the lateral buds down the length of that branch. Instead of the branch getting longer, it is now getting 'bushier.' More shading of the center of the tree, more non-productive branches and you'll end up with a bush on a stick.
What you want to be doing right now is allowing your fruit trees to get big enough to begin to produce fruit. Later on, you WILL want to control the size of your tree, prune to allow ventilation and maximize fruit production. At 8" I can't imagine what needs pruning. DON'T prune the 'leader!' Later on, you might have two or three branches vying for that position and you will have to decide which one and then one day you will remove the leader once it has reached the desired height for producing fruit you can reach. You'll learn how to prune for maximum fruit size and production.
Leave the little branches that grow from the trunk...or at least a few of them. They help to increase the trunk size for strength. And while I am thinking about trunks, don't stake your trees! The only time I ever stake trees is when I plant bare root trees or transplant mature trees with lots of canopy and have compromised root balls. Trees need to MOVE in the wind. This movement causes the tree to grow more root structure and thickens the trunk to protect against wind. Staked trees are being set up for failure. With their movement restricted (in essence telling the tree that the wind is always going to be but a breeze) the trunk stays skinny, the energy goes into the canopy instead, the root system stays whimpy and when the stakes are removed and even if they aren't removed the weight of the canopy WILL cause the tree to break or pull up roots falling over. I am terrible...I walk through parking lots during the winter (roots grow all winter) and cut the ties to the trees if they are leafless and out of danger. As well as those who have been forgotten and the ties are becoming part of the tree and will die from girdling or will break at the tie or will be blown over. At least they get a chance.
When planting a B&B tree, balled and burlapped tree from a nursery, the root ball is usually clay and all the roots that tree needs are all in that ball. I ALWAYS take the burlap off...completely (burlap is usually treated with chemicals that inhibit decay), unwind any roots that have encircled or are in danger of encircling the root ball, disturb the clay ball as little as possible, plant on top of undisturbed subsoil the exact depth of the root ball or an inch or two shallower to allow for mulch. If the soil is clay and it is planted in a more freely draining soil, I make a ring with soil around the circumference of the root ball and/or shove a piece of pvc pipe, 2"-4" diameter with holes drilled in the sides so that water gets into that root ball and isn't shed off the sides and into the native soil.
Your trees must have come in a pot or bare root? Main thing is to help you see what is happening below the soil. For now, only 'thin' to prune, fertilize sparingly, improve your soil by mulching with decomposed organic mulch within the drip line and past a few feet but NOT near the bark and to be patient for a couple of years. You'll have plenty of time before you need to make any other decisions about your trees...I hope I've answered your question and I apologize if all the other information you already knew and didn't need. Have fun...a few years go by awfully fast!
