If you're growing a juniper cultivar called "Spartan" (Juniperus chinensis "Spartan"), you're probably familiar with its tall, narrow shape. A Chinese juniper, this variety reaches 15 to 20 feet tall, but only grows 4 to 5 feet wide. Although this evergreen doesn't require regular pruning, a "Spartan" juniper that's getting too tall or has some spreading branches near its top can be trimmed back successfully, as long as you follow a few guidelines.
Choosing the Best Time
"Spartan" juniper grows in U.S. Department of Agriculture plant hardiness zones 5 through 10, becoming partially dormant in winter, when its growth slows. You can do a small amount of light pruning at any time of year, but if you're planning to do major pruning, it's best to postpone this until early spring, just before the dormant buds open and new growth appears. This takes advantage of the new flush of spring growth that begins soon after your pruning session, while also allowing you to remove any branches damaged or broken during winter storms. Avoid doing any major pruning in late summer.
Trimming the Top
To trim the top of a "Spartan" juniper, cut back the terminal end of each branch to remove the final, or apical, bud. This encourages growth of new side shoots, encouraging the plant to become more full and giving it a strong shape. Junipers are typical evergreens and can't produce new growth from brown, leafless branches, called "dead wood." When pruning, you can cut the branches back severely, but make sure you leave some green foliage on the plant and don't cut so drastically that only dead wood remains, because this can kill the shrub. To prune the top back more gradually, trim back about one-third of the branches in the first pruning session, then repeat this during the next two seasons to complete the job. Sterilize your pruning blades by wiping them with a cloth soaked in rubbing alcohol between cuts. This helps prevent the spread of plant diseases.
More Trimming and Tying
After you prune back the top of a "Spartan" juniper, watch the new growth to decide if you need to shape the tree some more. When side branches appear, you can prune back any that protrude outside the main canopy to help maintain the juniper's narrow, columnar form. If just a few branches need trimming, you can do this at any time. For more major trimming, delay until the following spring. If branches start to lean away from the main portion of the plant as they produce new growth, you can keep these in position by using soft ties or plastic connectors, which you can buy at nurseries, anchoring them to main branches to train them into position. Leave these in place until tender new growth strengthens, which can take a year or two.
Giving Extra Care
Junipers are generally tough shrubs that need little special care, tolerating drought and other tough conditions well. But after giving a "Spartan" juniper a major pruning, give the plant some extra care. Ensure it gets about 1 inch of water weekly, including water from rain. Water the plant during dry spells, especially in summer. Add a 3- to 4-inch layer of organic mulch under the canopy to help conserve soil moisture and keep down weeds. Don't let the mulch touch or rest against the plant's trunk, as this can encourage rot and disease.
- Missouri Botanical Garden: Juniperus Chinensis "Spartan"
- University of Florida: Juniperus Chinensis "Spartan" (Spartan Chinese Juniper)
- Landscape Advisor: How To Prune Upright Junipers
- Bartlett Research Laboratories: Pruning Junipers
- University of Georgia Extension: Junipers
- North Dakota State University Extension Service: Questions On -- Juniper
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