Arborvitae (genus Thuja) are popular evergreen conifers valued for their dense foliage and columnar or pyramidal shape, making them ideal for privacy screens or hedges. While they offer excellent year-round structure, planting companions alongside them introduces aesthetic variation and supports the overall health of the planting area. Thoughtful companion planting enhances visual appeal by adding contrasting textures and colors, transforming a simple hedge into a layered garden feature. This approach requires selecting partners that can coexist with the arborvitae’s specific environmental needs, ensuring both the evergreen and its companions thrive.
Understanding Arborvitae’s Growing Requirements
The success of any companion planting scheme begins with understanding the core environmental needs of the arborvitae. These conifers perform best in full sun, meaning a minimum of six hours of direct sunlight daily, though they can tolerate partial shade. Insufficient light can lead to thinner, less dense foliage, compromising their screening function.
Arborvitae are adaptable but require moist, well-drained soil to prevent root issues. They are intolerant of overly saturated, “soggy” conditions, which can quickly predispose them to root rot. The preferred soil reaction for Thuja is slightly acidic to moderately alkaline, typically pH 6.5 to 8.0. Companion plants must tolerate these conditions, especially consistent moisture without waterlogging, which minimizes competition and ensures the entire planting area can be managed uniformly.
Low-Growing Companion Plantings
Selecting low-growing plants for the base of arborvitae hedges serves the practical purpose of weed suppression and moisture retention while providing a finished look. These plants should have non-aggressive root systems so they do not compete with the arborvitae’s shallow feeder roots. Groundcovers like Creeping Jenny (Lysimachia nummularia) offer a vibrant yellow-green contrast to the dark evergreen foliage and appreciate the same moist soil conditions.
In areas where the arborvitae casts substantial shade, particularly on the north side of a dense hedge, shade-tolerant plants are necessary. Hostas are a classic choice, offering large, textured leaves that contrast sharply with the conifer’s fine foliage. Wild Ginger (Asarum canadense) is another option, a native groundcover with heart-shaped leaves that spreads slowly via creeping rhizomes. For different texture, Japanese Sedge Grass (Carex morrowii), especially variegated cultivars, creates a graceful, arching effect at the base of the trees.
High-Contrast and Decorative Companions
Introducing plants that offer a dramatic contrast in color, texture, or form significantly enhances the uniform green backdrop of arborvitae. Shrubs with deep purple or red foliage, such as Japanese Barberry (Berberis thunbergii) or Purpleleaf False Holly (Osmanthus heterophyllus ‘Purpureus’), provide a striking color foil. These rich hues pop against the neutral green, especially in full sun.
For a softer, more dynamic texture, ornamental grasses are an excellent pairing, introducing movement that contrasts with the static, solid form of the arborvitae. Mid-sized flowering shrubs, such as Hydrangeas, work well because their large, showy flower clusters and broad leaves offer a completely different visual mass.
Texture and Movement Companions
- Clump-forming varieties like Blue Fescue (Festuca glauca) or Maiden Grass (Miscanthus sinensis) offer fine, wispy foliage and plumes.
- The blue or silver tones of fescue provide a cool color contrast against the dense green foliage.
- Oakleaf Hydrangea (Hydrangea quercifolia) provides seasonal interest with its distinct foliage shape and peeling bark.
- Hydrangeas generally tolerate the partial shade that many arborvitae hedges create.
Perennials that offer long-lasting color and varied forms can be layered in front of the hedge line. Daylilies (Hemerocallis) are a resilient choice, providing vibrant, trumpet-shaped flowers and are moderately drought-tolerant once established. Plants like Coneflowers (Echinacea) introduce a classic meadow look with their daisy-like blooms, attracting pollinators and adding a splash of color against the dense green background.
Plants That Should Be Avoided
Successful long-term landscaping requires avoiding species that actively compete or clash with the arborvitae’s needs. A primary concern is root competition; plants known for aggressive or shallow spreading root systems should be excluded. Running bamboos, for instance, have rhizomes that can quickly infiltrate and choke the arborvitae’s root zone, restricting nutrient and water uptake.
Another incompatibility arises from differing soil pH requirements. Arborvitae prefer a neutral to slightly alkaline soil, which means plants that thrive in highly acidic conditions should be avoided. Classic acid-loving plants, or ericaceous species, such as Rhododendrons, Azaleas, and Blueberries, should not be planted directly alongside arborvitae. Attempting to amend the soil for one group will negatively impact the other, leading to nutrient deficiencies and poor growth. Finally, the aversion of arborvitae to “wet feet” means that true wetland or bog plants, which require constantly saturated soil, must be avoided. Planting water-hungry species like Cardinal Flower (Lobelia cardinalis) nearby would necessitate overwatering the area, increasing the arborvitae’s susceptibility to fungal diseases and root rot.