Eastern arborvitae, scientifically known as Thuja occidentalis, is a coniferous tree native to North America. While it is often associated with hedges and windbreaks, this versatile species can be styled as a bonsai. Its unique characteristics make it both a fascinating and challenging choice for bonsai. In this article, we’ll explore the advantages and disadvantages of cultivating eastern arborvitae as a bonsai tree, along with insights into its care and styling.

Unique Characteristics of Eastern Arborvitae

Eastern arborvitae is characterized by its soft, scale-like foliage, which grows in flat sprays. The tree’s natural growth habit is conical, with dense branching and a rich green color that can take on a bronze hue in winter. It’s a hardy species, thriving in USDA zones 2-7, and is known for its resilience in various soil types and conditions.

These characteristics make eastern arborvitae a potential candidate for bonsai cultivation, but its natural traits also present specific challenges. Let’s delve into the advantages and disadvantages of growing this tree as a bonsai.

Advantages of Growing Eastern Arborvitae as a Bonsai

  1. Hardiness: Eastern arborvitae is highly tolerant of cold temperatures, making it an excellent choice for outdoor bonsai in colder climates. It can withstand harsh winters and adapts well to various soil conditions.
  2. Compact Foliage: The fine, scale-like foliage of eastern arborvitae lends itself well to creating a refined, delicate appearance in bonsai. Its dense growth pattern can be shaped into intricate designs.
  3. Natural Shape: The tree’s natural conical shape and strong apical dominance provide a good starting point for upright and formal bonsai styles. With proper pruning, the tree’s branching can be developed to emphasize a traditional bonsai aesthetic.
  4. Readily Available: Eastern arborvitae is widely available in nurseries and garden centers, often at an affordable price. This accessibility makes it an appealing choice for beginners looking to experiment with bonsai techniques.
Eastern Arborvitae
photo by:
jnshaumeyer © as displayed on Flickr (Licensed under CC BY 4.0)

Disadvantages of Growing Eastern Arborvitae as a Bonsai

  1. Brittle Wood: One of the biggest challenges with eastern arborvitae is its brittle wood. Branches are prone to snapping under stress, making wiring and shaping more difficult compared to other species like junipers or pines.
  2. Foliage Browning: The tree’s foliage can turn brown in response to stress, overwatering, or poor air circulation. This discoloration is not only unsightly but may also indicate underlying health issues.
  3. Limited Style Options: Due to its natural growth habits and brittle branches, eastern arborvitae is best suited for upright and informal upright styles. It’s less flexible for other bonsai styles like cascading or windswept, limiting creative possibilities.
  4. Unreliable Back-Budding: There’s no consensus “back-budding rules” in the bonsai community for eastern arborvitae. Some believe that once a branch “turns brown” (i.e. lignifies) that it will not back-bud, while others have much more confidence in thuja’s ability to back-bud. Because of this, it’s best to start with younger trees, which are generally more able to back-bud, and develop a plan for your bonsai’s long-term structure fairly quickly.
  5. Deer Delicacy: It’s a common occurrence to see landscaping arborvitae chomped down by deer in the winter. Hungry deer could spell an end to a miniaturized arborvitae. Remember to protect it with fencing, a cold frame, or an unheated structure in the winter.
  6. Winter Light Requirements: Unlike deciduous trees which lose their leaves in the fall and therefore do not need light in the winter, conifer trees do require some light. Thuja trees require more light than other conifers. If overwintering your tree in a structure like a shed or an unheated garage, be careful to provide some light for the tree.    

Tips for Styling and Care

  • Pruning: Regular and careful pruning is essential to control growth and shape the tree. Avoid heavy pruning in one session, as this can cause stress and browning. Notion Bonsai says that 50% of the foliage can be safely removed in a session.
  • Wiring: When wiring branches, proceed with caution to avoid breakage. Use light wiring techniques and support branches as needed.
  • Watering: Eastern arborvitae prefers consistently moist but well-draining soil. Avoid overwatering, as this can lead to root rot.
  • Sunlight: Provide full sun to partial shade for optimal growth. Ensure adequate air circulation to prevent fungal issues.
  • Winter Protection: Although hardy, potted bonsai trees are more susceptible to root freeze. Protect your arborvitae bonsai during extreme cold by mulching or placing it in a sheltered location.

Conclusion

Eastern arborvitae (Thuja occidentalis) offers both unique opportunities and challenges for bonsai enthusiasts. Its hardy nature and compact foliage make it an attractive option, while its brittle wood and growth habits require patience and skill to manage. With the right care and styling techniques, this tree can be a rewarding addition to any bonsai collection. Whether you’re a beginner or an experienced bonsai artist, the eastern arborvitae provides a unique canvas for creativity and cultivation.