How Deep Do Arborvitae Roots Grow?

Spread Those Roots Far and Wide

• Arborvitae roots stay in the top 9 to 12 inches of soil as they spread horizontally in search of oxygen, moisture and nutrients. The extremely thin, fibrous roots push through soil particles to past the drip line for strong anchorage. As roots encounter moisture, they absorb both water molecules and critical elements for uptake to the canopy above. Mature arborvitae have extensive ground roots that effectively hold the soil in place for erosion control, but they do not form aggressive roots that damage walkways or home foundations.

Give Them Some Breathing Room

• Newly planted arborvitae have dense root balls that need time to spread in the soil. Create a large planting hole about twice the diameter of the root ball when transplanting. Remove any protective burlap from the roots to encourage rapid establishment. Any barriers to root-spread hinder transplant success, and your arborvitae may show signs of stress or growth stunting. When you firm the loose soil around the exposed roots, moisture and oxygen exchange begins. Roots slowly spread horizontally with some vertical development for safe anchorage.

Inspect That Soil Type

• If your soil is sandy, arborvitae roots may grow deeper than 12 inches. Similar to a desert environment, sandy soil does not hold water well, forcing arborvitae roots to dive deep for moisture access. In contrast, a particularly moist soil site, such as near a leaking sprinkler pipe, encourages arborvitae roots to grow toward the consistent moisture for sustenance. In a nutrient-rich and well-drained soil site, the roots grow in a normal horizontal shape surrounding the arborvitae.

Water It Slow and Steady

• Water your arborvitae to a 24-inch depth, so the entire root system receives uniform moisture. Insert moisture meters into the soil for an accurate account of your irrigation practices. Soggy soil encourages root rot while dry conditions create foliage browning and dieback. Mulch spread to a 3-inch depth around the tree or shrub conserves soil moisture for ample root uptake. Do not pile mulch around the trunk, however. Bark rot may set in and damage the arborvitae.