Arborvitae (Thuja) are favored evergreen trees often used for dense privacy screens or as specimen plants. These conifers naturally develop a thick, conical or pyramidal form, making their dense foliage a common sight in many landscapes. Homeowners frequently consider trimming the bottom branches to manage size or change the plant’s appearance. Understanding the unique biology of the plant is necessary before making any cuts to the lower canopy.
The Permanent Result of Cutting Into Old Wood
Arborvitae tissue does not possess dormant buds on old wood that can be activated to produce new foliage. Unlike many deciduous shrubs that can be heavily pruned, Thuja only produces new growth from the actively green, younger parts of the branch tips. If a branch is cut back past its current year’s green growth and into the brown, woodier interior section, that part of the plant will not regenerate.
This non-regenerative nature is the most important factor when trimming the bottom of the plant. Removing lower branches entirely or cutting them back too aggressively exposes the bare, internal wood, creating permanent, brown gaps. The resulting bare area remains exposed for the plant’s lifetime, as the remaining green foliage will not grow downward to conceal the cut. Trimming the bottom branches results in a permanent structural change.
Practical Reasons for Limbing Up Arborvitae
The process of removing lower branches, often called “limbing up” or “skirting,” is driven by maintenance and design needs. A common motivation is to create necessary clearance around structures or pathways. Removing the lowest growth allows for easier pedestrian access, keeps foliage from dragging on the ground, and simplifies maintenance tasks like mowing or edging turf near the tree base.
Removing the dense, lower branches significantly improves air circulation around the base of the plant. Stagnant air and high humidity trapped beneath the thick foliage can create an environment conducive to fungal growth and moisture-related diseases. Increasing airflow helps maintain the plant’s health by keeping the inner structure drier. Many people also limb up arborvitae to transform the plant from a shrub into a more formal, tree-like specimen, exposing the trunk for a different architectural element.
Essential Techniques and Timing for Lower Branch Removal
The optimal time for structural pruning is during the dormant season, typically late winter to very early spring, just before the first flush of new growth. Pruning during this period minimizes stress on the tree and promotes rapid healing. Cuts made in late summer or fall can stimulate tender new growth that may be damaged by winter cold, so these times should be avoided.
When removing an entire lower branch, the cut must be made flush with the trunk or the main stem. Make this cut carefully, avoiding damage to the “branch collar,” the slightly swollen area where the branch joins the trunk. The branch collar contains specialized cells that facilitate the natural wound-closure process.
For larger branches, the three-cut method is recommended to prevent the branch’s weight from tearing the bark down the trunk. The initial cut is an undercut made a few inches away from the trunk, followed by a top cut to remove the bulk of the branch. The final cut removes the remaining stub outside of the branch collar. Perform this structural trimming conservatively, stepping back frequently to assess the balance and height of the remaining canopy, as removed material cannot be replaced.