Pruning

The basic principle of pruning is that growth within a plant is Darwinian. Branches and leaves grow where they find resources. If a leaf does not find enough light and air to photosynthesize, it will die. Needles are a form of leaf, so the same principles apply to evergreens.

The tip of each stem has what is called a growth tip, which is (not surprisingly) where growth occurs. Each growth tip also releases something called apical hormones, which attempt to inhibit growth in nearby areas. You can see these hormones in action when you look at a branch: if there are side-branches near the tip, they are generally smaller and weaker than side-branches further back.

When you prune off growth tips, you release growth elsewhere. One of the big mistakes people make when they prune is that they think of pruning as restricting the plant’s growth when it is actually releasing the plant’s growth. As you contemplate each cut, think about where you want to release growth.

Use a blade to make a sharp clean cut that will heal quickly. Don’t rip the poor plant!

Start by removing dead wood. Pull leaves and branches at least 9”, preferably more, from any buildings. So far this process is pretty routine.

Then comes the fun part. Visualize what growth you would release by one cut, by another cut, by another cut. Where do you want the plant to go? Open up the interior so that all parts of the plant get light and air; this will encourage growth in the middle (remember, no leaf will grow if it can’t get light) and decrease the chances of fungal infection. Remove branches that are crossing and may rub against each other in the wind, and so open up sites for infection. Step back and think about the aesthetics of the plant’s shape.

I find that pruning at this stage requires an intense concentration, as I try to keep in mind what the plant is, what it might possibly become, and how my actions will play out over the years. I can’t talk while I prune a plant: it requires my complete attention.

In general, late winter and early spring are good times to prune – before the plant puts energy into growing things you are going to cut off. The exception is plants that have already set their buds before winter, such as rhododendrons. They should be pruned after they finish blooming but before they have started to invest energy in setting buds for the next year.

Pruning in the late summer and fall is dangerous. The wound may not have enough time/energy to heal before winter, and any new growth is likely to die in the winter. The exception is dead wood, which can be removed at any time.

For more detailed information about specific plants, Google is your friend.

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