An introduction to pruning

As a plant geek, one of the things I tend to notice is BAD pruning jobs. Ask my daughters and they will agree that this is something I am oddly, and annoyingly, fixated on. Pruning done well is not noticeable, except maybe a brief observation of “That’s a nice tree”. Pruning done badly is an eyesore for a long time and is most visible in winter.

Trees have a single trunk under natural conditions. Shrubs have multiple trunks. That's what makes them shrubs. Some shrubs are made into trees, but they often react by sending up other shoots around the base of the trunk.

Most trees look great with leaves, but the foliage may be hiding a lousy branching structure. If you look at your trees in winter, you can really see what is going on.

While mature tree canopies vary by species, young trees should have a common structure. They should have a central leader, the main branch up top that will be the tallest part of the tree. For any number of reasons, the nursery will sometimes cut off this leader branch. This causes side shoots to branch out and changes the natural shape of a tree. This can make a tree have a poor branching structure and only careful pruning can pull it back into shape. Sometimes you can’t fix it at all.

Fruit trees are an exception to this. They are often pruned to keep the branching structure low and wide for easier access to the fruit.

Look at the trees in your yard before the leaves emerge. If there is a tangle of branches, you need to prune! Take a look at the pictures at the end of this post to get an idea of what you should watch for.
Larger trees need a professional. Get a good one, a certified arborist who understands tree structure and anatomy. A mature tree that is cropped off breaks my heart. That kind of pruning shortens the life of the tree, and it looks terrible.
 
If you have a younger tree that you can work on without falling off a ladder, get a good pruning saw, sharp pruning shears (there are left handed models and if that is you, BUY THEM!), and a really good, sharp tool, called a lopper. It is a long handled pruning shear. It is worth getting good tools if you are going to garden. It makes every job easier.

Please, don’t ever prune a tree with hedge trimmers. Don’t turn a tree into a lollipop. Don’t prune when you are angry. I could give you many lessons in pruning, but it is an art and a science and there are numerous, well-illustrated sources out there. Check out YouTube.

Be aware that different sized trees may have different pruning needs. I think of ash, large maples, locusts, lindens, etc., as street trees. They are quite large when mature and their lowest branches are generally high. So you would gradually remove the lowest branches. Crabapples on the other hand, are smaller when they are mature and you should keep their branches lower to the ground.

Some important points to consider:

• Walk around the tree and look at it from all angles. A tree lives in 3 dimensions. A branch that looks good from one side may be crossing or interfering with a branch on the other side. Try to visualize what the branch will do when it grows thicker and bigger around. 
• Plan cuts to open up the center of the tree. 
• Shorten a branch with a cut just above a bud, but don’t damage the bud. Remember that the bud will turn into a branch. It will be the endpoint of the sap and water that is rising up from the roots. Anything above the bud will die and leave a stub that will poke somebody’s eye out. 
• Pick a bud that will grow in the direction you want. A bud that points to the center of the tree will grow a branch that will head into the center of the tree, which is something you don’t want. 
• Don’t get over-zealous. A good rule of thumb is to prune only 1/3 of the total branches in a year so you aren’t removing too many future leaves. 

I will also add – once you have cut the branch off, it is gone. Think before you cut!

Finally, here are some good examples of common problem tree structures to help you identify what your trees might need.

This is a young tree growing a double leader. The leader on the left is the better one, because it will produce a straighter, mature tree. A careful removal of the longer leader on the right will allow the smaller one to become dominant. This is an example of the benefit of walking around the tree. From one side, the longer leader was the more obvious choice because you couldn’t see its curve.

This tree in my neighborhood has too many interior branches, but a good straight leader. Careful selection of branches and pruning over several years will open this up to make it a great mature tree.

This tree would be very difficult to improve. There are too many trunks and removing a couple of them would make the tree appear lopsided or deformed because it has grown to adapt to its overcrowding. As the tree matures, it is likely those trunks will rub together and damage each other.

This tree should have been pruned when it was younger. There are too many branches coming off of the center trunk. Careful removal of the 2 weakest, thinnest branches this year and maybe one more next year will improve the shape of the mature tree.