How Do I Prune Junipers in Containers?

Save pruning effort by fitting your juniper to its container.

Save pruning effort by fitting your juniper to its container.

Junipers (Juniperis spp.) are slow-growing evergreens that thrive in containers with conservative pruning. Trees in containers have several advantages. They fit in small spaces and can decorate areas, such as patios, where trees can't be planted. They can also be moved to avoid the heat of summer or winter cold, stretching areas where they can grow by as much as a U.S. Department of Agriculture plant hardiness zone.

Juniper Basics

Junipers grow in a variety of shapes and sizes, but all junipers love sunshine and well-drained soil. They adapt to a variety of soil textures, pH levels and fertility -- and stand up to winter winds, making them good choices to provide windbreaks for delicate plants or windswept patios. Junipers are orderly conifers, growing slowly and requiring only light pruning to keep their attractive shapes, Growth typically takes place through spring into early summer. Remove damaged or infected branches any time you find them on your plants. Clean tools with household cleaner or rubbing alcohol between uses to avoid transmission of diseases. Clean blades more frequently when cutting branches with obvious disease. Junipers' two leaf types require slightly different pruning techniques.

Scaled-Leaf Junipers

When you cut back a juniper with scaled leaves, new branches and leaves do not sprout, so conservative, well-planned pruning is imperative. Many Chinese junipers and fitzers are hardy in USDA zones 3 through 9, including the Shimpaku (Juniperus chinensis “Shimpaku”) and Armstrong (Juniperus x fitzeriana “Armstrongii”) hybrids. These dwarf trees grow to 3 or 4 feet tall but can grow up to 4 or 5 feet wide. Using sharp hand shears or bonsai pruning scissors, remove only shoots growing beyond the crown, or foliage pad edge, far enough into the foliage so green scales conceal cut ends. Timely removal of overgrown branches trains other branches to remain compact.

Needle-Leaf Junipers

Junipers with needles require attentive pruning because each branch produces light new growth, called candles, each spring. Once growing slows in early summer, snip off the entire candle on the end of each branch with shears or scissors. Each spring, check for new branching caused by candle removal to keep a compact form to needle-leaved junipers such as singleseed (Juniperus squamata “Blue Star”), hardy in USDA zones 4 through 8.

Life in a Box

Pots and planters provide portability, but they also confine spreading juniper roots, so invest in dwarf trees or match containers to the adult dimensions of their residents. You'll save yourself the periodic re-planting and plant loss inherent in forcing junipers to fit too-small spaces by over-pruning. Find containers large enough to provide about 2 cubic feet of soil for every square foot of canopy of a tree of adult size. Ensure that containerized plants receive at least 1 inch of water per week -- sink a tuna can in the corner of the container to measure -- and provide extra water after planting or pruning. Your junipers need extra nutrients, too, so feed them with evergreen plant food such as 16-4-8 or 12-4-8 at a rate of 1/2 pound per 100 square feet each spring before new growth begins.

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