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Appropriate spacing
As these Green Giant arborvitae mature, their canopies are just beginning to touch at the bottom.
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Plant diversity
Using a variety of plants provides a green screen with visual interest and restricts overall susceptibility to insect or disease problems.
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A common problem
Disease and death can mar a screen of Leyland cypress trees if they are planted too closely.
“What’s wrong with my Leyland cypress screen?”
Statewide, this question is all too common at Clemson Extension offices. Fast-growing evergreen trees, like Leyland cypress, are a popular landscape choice for blocking out undesirable views or nosy neighbors. Unfortunately, Leylands are susceptible to insects, disease and other maladies when planted too close together, a fact many homeowners forget in the rush to create a dense living wall around their property.
If an instant screen is what you need, build a privacy fence. Seriously. A fence is faster and more effective. You can always plant evergreens in front of the fence if you prefer a view of leaves to boards—just allow the plants the space they need to grow strong and healthy.
If you have time to wait for a green screen to grow in, plant a mixed hedge. Don’t fall for the substitution theory that a single row of Green Giant arborvitae (or any other evergreen plant) will avoid the problems common to Leyland cypress. It won’t. Planting dense rows of any one type of plant is called a monoculture, and it’s setting yourself up for failure. If one succumbs to disease, the others will all be susceptible.
By planting different kinds of plants in a living screen, you can (pardon the pun) hedge against disease and pest problems. Consider mixed plantings of hollies, magnolias, and cedars or junipers. These groups aren’t closely related, so they don’t share many insect pests or diseases. If one type of tree becomes infected or dies, it won’t ruin the look of your screen.
If you have enough space, stagger your plants instead of planting in a straight line. This will give your planting visual depth and make it more forgiving if you lose a plant or two.
Regardless of the plants you choose, space them appropriately. Landscape trees and shrubs should be spaced according to their mature canopy spread. When young plants grow together and develop interlocked canopies, it blocks natural sunlight and airflow, creating the perfect environment for plant stress and insect or disease infestations. Intertwined roots of closely planted trees may also compete with one another for water and nutrients, leading to additional stress. Canopies can become misshapen, unsightly, flat-sided or even bare on one side.
Do your homework on screening plant options—determine the mature size, width and height before planting. Then base your choice and spacing on that information. Leyland cypress trees, for instance, mature at 60 to 70 feet tall and 12 to 15 feet wide. I recommend 12-foot spacing as the minimum distance apart to avoid problems, but 15 to 20 feet would be even better. If you want to space young plants more closely just to start, try a 6-foot spacing, but be sure to remove every other tree as soon as their canopies begin to touch.
S. Cory Tanner is an area horticulture agent based in Greenville County. Contact him here.
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Get More
For more screening ideas, visit Clemson Extension’s Home & Garden Information Center at clemson.edu/hgic.