Late June through mid-July is the best time to lightly shear new growth while it is still pliable and easy to bend, said Bert Cregg, a Michigan State University professor of horticulture and forestry.
A good rule of thumb is to prune pines when the current year's needles are half the length of the previous year's needles, typically no later than mid-summer, Cregg said. For small pines, new shoot growth can be controlled by pinching off at the desired height.
The Right Cut
Pruning pines is different from deciduous trees; they are far less forgiving, cautions Vic Foerster, an arborist with West Michigan Tree Services and vice president of the Arboriculture Society of Michigan.
"All conifers are unique, they grow in whorls, they don't re-sprout from where you cut it, there are no suckers growing behind it,' Foerster said. “Conifers only grow at the branch tip, so it presents unique challenges.'
The annual task of pinching back new growth is underway at thousands of tree farms where conifers are grown for the fresh-cut Christmas tree market. Workers shear new growth, called candles, at an angle using razor sharp machetes. The goal is to remove one-third to one-half of the new growth year after year so branches grow in a tight, conical pattern.
Try It Yourself
Homeowners can achieve the same affect using hand shears or hedge trimmers. Remove a third of the new growth from top to bottom, cutting the tender tips at an angle.
This is particularly helpful for trees that are misshaped due to storm or insect damage. After a few seasons, branch proportions return to a more natural-looking form.
Some Christmas tree growers prune firs and spruces later in summer after bud-set, while others prune in early spring before growth resumes. Pruning branch tips stimulates additional bud development along the stem, resulting in dense growth.
Know Your Trees
Eastern white pines are easily identified by groups of five long, thin, soft needles. Red pines have groupings of two long needles. To maintain a compact appearance on a red, white or Scotch pine, trim the candles on the tree's tops and sides.
If you want the tree to grow a little, wait until the candles are 2 inches to 4 inches long, and then pinch or clip off only the tips, recommends author Lewis Hill in his book, "Pruning Made Easy."
Pruning new growth is easy; cleaning the sticky sap from your hands is not. Wear a pair of gloves; be they leather work gloves or clear latex gloves, to protect your skin from the sticky sap mess. Once done, clean sap from your tools before it hardens.
John Hogan - John Hogan is a journalist with more than two decades of professional experience covering everything from homicides to hostas. He is ...
