Arborvitae are popular evergreen trees, often chosen for their dense foliage and versatility in landscaping. Understanding their root systems is important for successful cultivation, ensuring healthy growth and preventing common issues.
Understanding Arborvitae Root Systems
Arborvitae typically develop a fibrous, shallow, and spreading root system. These roots branch out horizontally rather than forming a single, deep taproot like some other tree species. The majority of an arborvitae’s roots are found within the top 12 to 18 inches of soil, though some can extend to 18 to 24 inches deep. This extensive system anchors the tree and efficiently absorbs water and nutrients from the upper soil layers.
The extent of this root spread can be considerable, often reaching a width similar to the tree’s canopy. For instance, a 10-foot-tall arborvitae might have roots spreading 10 to 15 feet laterally from its trunk. This wide, shallow network is characteristic of their growth habit, allowing them to thrive by efficiently capturing surface moisture and available nutrients.
Factors Influencing Root Depth
Several environmental and care-related factors directly impact how deep arborvitae roots will grow. Soil type is a significant determinant; roots will penetrate more easily and deeply in loose, well-drained soil compared to dense, compacted clay. Clay soil, while holding water well, can impede root growth due to its density. Conversely, loose, fertile soils with good drainage allow roots to expand downward more readily for water and nutrients.
Watering practices also play a crucial role in root development. Consistent, deep watering encourages roots to grow downward, seeking moisture deeper in the soil. Conversely, frequent, shallow watering can lead to a less robust, more surface-oriented root system. The age and size of the arborvitae also influence root depth; younger trees initially focus on above-ground growth, while mature trees develop more extensive and deeper root systems for stability and access to deeper water. Different arborvitae varieties, such as the vigorous ‘Green Giant’ versus the more compact ‘Emerald Green’, can exhibit differences in root habits, with ‘Green Giant’ often developing a more extensive system.
Implications of Root Depth
Understanding arborvitae root depth has practical consequences for landscape planning. Their shallow, fibrous root systems are not highly invasive, making them less likely to damage foundations, sidewalks, or driveways. However, maintain a distance of at least 3-4 feet from a house and 18 inches from a driveway when planting near structures.
The relatively shallow nature of their roots can impact the plant’s stability, especially in high winds or loose soil conditions. A deeper, more established root system provides better anchorage, reducing the risk of the tree toppling. The wide spread of their roots can compete with other nearby plants for water and nutrients, necessitating proper spacing. While established arborvitae can tolerate dry spells, their shallower root system means they may require supplemental watering during prolonged drought conditions.
Managing Arborvitae Roots and Planting Practices
Effective planting practices encourage healthy root system development. When planting, dig a hole that is two to three times wider than the root ball, but only as deep as the root ball itself. This provides loosened soil for horizontal root spread and ensures the tree is not planted too deeply, which can lead to root rot. The top of the root ball should be level with or slightly above the surrounding soil surface.
Consistent deep watering is important for establishment, encouraging roots to grow downward. After planting, water two times a week for the first 60 days, especially during dry periods. Applying a 2-3 inch layer of organic mulch around the base of the tree helps conserve soil moisture, regulate soil temperature, and suppress weeds that compete for resources. Avoid placing mulch directly against the trunk to prevent moisture buildup and rot.