Pine trees (Pinus spp.), while stately and lovely, can grow anywhere from 4 feet to well over 100 feet tall, depending on the species. Before buying a pine tree, consult with your local garden center to learn about types available in your hardiness zone and how tall they grow — and for advice regarding required maintenance. If you already have pine trees in your yard and they haven't grown out of control, you can try to hold them to a specific size temporarily, but they'll still escape and grow. Pine trees are temperamental, and one wrong cut can kill the tree.
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Curtailing Pine Tree Growth
You can't trim a pine tree just by cutting into a branch and letting it drop. That removes the bud at the end of the branch, causing the branch to die. The crown of the tree and the candles are where you want to aim your cuts to keep from destroying the tree. Pine tree cutting and trimming should be done in late winter and early spring. And before you get started, be sure to familiarize yourself with the parts of the pine tree you'll be dealing with:
- The crown: the very top of the tree, often called the leader. Visualize where you put your Christmas tree topper. That's the crown. Often there are two leaders, and you must cut both.
- The candles: new growth extending outward and upward from the tip of the branch, resembling candles. Lighter green in color and softer to the touch, they should be nipped by hand — never by a tool.
- Whorls: groups of branches with trunk growth between sets of whorls
Cutting the Crown
If the tree is tall, use a ladder with someone spotting you from the ground and stabilizing the ladder. Cut the crown down to a bud that is facing north. The remains should be about 8 inches long. If you're cutting deep, keep moving down the trunk to a spot that is just above a whorl. Don't cut between whorls, and don't cut more than 20 percent of the tree's overall height.
Cutting the Candles
Growing in clusters, a dominant candle is surrounded by lesser candles marking the spring growth of the pine tree. You must trim every candle to control the tree's growth or they will evolve into branches. While growth is controlled, it isn't stopped. The tree will get bigger over time.
Candles grow out of branches, and if you let them grow, the tree becomes spindly and wide. Control the width of your pine tree by cutting the candles at their halfway mark. New buds will grow and add to the density of your foliage. This needs to be done every year.
Pay Attention to Whorls
Growing in a circular pattern from the trunk of the pine tree, each whorl represents approximately one year of growth. Small branches growing between whorls aren't counted. The whorl has two components: the buds and pine needles that populate the active section and the needles that end at the inactive section. When trimming the whorl, don't cut the inactive section. This will result in no new growth, leaving your pine tree with a naked branch.
- University of Maryland Extension: Pruning Trees
- Chicago Tribune: Not Like Other Evergreens: Pine Trees Require Special Pruning
- American Arborists: Tree Topping vs. Crown Reduction: What’s the Best Way to Deal With a Tree That’s Too Big?
- Open Oregon: Field Technique Tips for Counting Whorls
- The Highlands Current: Roots and Shoots: Pruning Pine Trees
- Seattle Japanese Garden: Candling: The Art of Japanese Pine Pruning