Pruning, Part 2

So, as promised: Pruning, Part 2.  Today I'm going to talk about how to prune woody plants.  This includes bushes and trees, though I'm not going to say a lot about trees because that's not where I have any experience.

I've pruned woody plants with Phil and Josh.  Reminder:  Phil works in Gymnosperm Slope and Comstock Knoll (the rhododendron garden), and Josh works in the winter garden. 

First things first:  why would one want to prune a woody plant?

Josh says: There are a few reasons.
1) Plant health.  Pruning lets air and light get between a plant's branches and leaves.  This is important for a few reasons.  First, plants need air (CO2) and light on their leaves to photosynthesize.  Second, if air and light cannot get in, this creates a moist environment that's perfect for fungus growth.
2) Break up plant fights.  If you have two bushes next to each other in your garden, eventually they may start to grow into each other.  Josh calls this a plant fight.  When plants fight, it's not pretty.  It looks messy, and often the branches beneath the plant fight will die because they aren't getting enough light.  This leaves you with an ugly hole in your bush when you cut back the offending plant.
3) Remove dead stuff.  Dead stuff is ugly.  Once it's gone, it can let more light and air in to the live branches of the plant.
4) Prettify.  Sometimes you want your hedge to look flatter.  So you prune it.
5) Some plants really benefit from being cut back.  This allows them to produce health new growth.

One day, I helped prune forsythia on Gymnosperm Slope.  Forsythia are one of those bushes that really benefit from being cut back.  Here's a picture of a young forsythia plant blooming in the spring:

Picture from Wikipedia

These bushes grow extremely fast!  The forsythia I was pruning had branches that were so long they bent over and touched the ground.  One had even taken root again!

How did I prune this forsythia plant?

I cut it all the way back to the ground!!!!!

Forsythia, as well as dogwood bushes, will often begin to grow new branches from their base. Because these bushes are so good at growing new branches, you can often just cut all the old branches right back to the ground, and the plant will grow a new set of branches in no time!

This is Bob, one of my fellow interns, cutting back some bushes about two weeks ago.

The bush in the back of this picture still has all its old branches, plus one little new one.  The bush in the front of the picture only has one little leafy branch left!  Bob cut all its other branches back to the ground.  But it will be just fine.  By the end of the summer it will be a bushy bush again.

So, that's one method of pruning.  Just make sure the bush you have can handle it.  :)

What if you only want to trim a few branches off of your bush, instead of trimming your whole bush back?  How do you do that?

Well, Josh has some answers for us here.

Josh says: Obey the rule of thirds.  The rule of thirds states that you should never prune a branch back to a branch that is less than 1/3 its size.  You should also, in general, never remove more than 1/3 of the volume of a bush at one time.  (Neither of these rules apply if you're using the pruning method I described above.)

The second part of the rule of thirds is pretty straightforward.  I'll explain the first part in a little more detail.

Usually, when we prune, we want to leave our bushes looking natural.  We don't want them to look like "poodle bushes," as Phil calls them: bushes that are perfect squares or perfect circles.  So, each time we trim a branch, we trim it back to the point where another branch branches off.

Let's say I want to get rid of the top branch in this picture.

I'm going to cut it back to the point where it V's:

Voila!

You see how the branch that's left, the bottom branch of the "V," is smaller than the branch I cut off.  Yet, it's not less than 1/3 of the size of the branch I cut off.

What if I wanted to make the branch in the picture below shorter?

Should I cut it here?

No!  The branches I'm cutting back to are too small.  They are less than 1/3 the size of the branch I would be removing.  In this case, I would have to continue down the branch I want to cut until I found a big enough branch to cut back to.

Why do we cut back to branches like this?  Well, it helps our bushes keep a natural look.  Also, plants have "buds," or places that can sprout new branches, in each branch's branching point.  So, by cutting back to the branching point, we're cutting back to a place where the plant can grow a new branch.

Last point about pruning:  When you are pruning a tree, never cut your branch all the way flush to the trunk or second branch.  Woody plants have something called a "collar" that grows at the base of each branch.  The collar is the bulging part at the base of the branch.  The collar will grow over a wound left by trimming so that pests can't get down into the wood.  If you cut flush to the branch, the collar will be damaged and the tree won't heal well.

Here's a link to a page that has good pictures of how to cut at the collar of a branch: http://treecarepruningandplanting.com/branch-collar.htm

That's all for now!  A final word about pruning next time.