Fertilizing Emerald Cedars in Ontario: A Comprehensive Guide for Year-Round Health


Emerald cedars (Thuja occidentalis 'Smaragd') are a beloved choice for homeowners in Ontario, known for their lush, evergreen foliage and the privacy they provide. To ensure your emerald cedars remain healthy, vibrant, and continue to thrive throughout the seasons, proper fertilization is essential. In this detailed guide, we will explore the ins and outs of fertilizing emerald cedars in Ontario, with a focus on when and how to apply fertilizers for optimal results.

 Fertilizer Fundamentals: 

Nitrogen (N), the first number, promotes foliage and green growth. For Emerald Cedars, a high nitrogen content supports their dense, green foliage, making it an essential component for their growth.

Phosphorus (P), the second number, is crucial for root development, flower, and fruit production. Bonemeal, with its high phosphorus content, is ideal for new plantings, including Emerald Cedars, aiding in establishing strong root systems.

Potassium (K), the third number, contributes to overall plant health and resistance to disease. While not the primary need for initial planting phases, it's vital for long-term health.

 The Timing of Fertilization:

Fertilizing your emerald cedars at the right time is crucial for their overall health and appearance. There are two primary instances when you should fertilize your cedars:

  1. Once Planted:

    When you first plant your emerald cedars, it's essential to give them a strong start. Using a balanced fertilizer like bonemeal is an excellent choice. Bonemeal is rich in essential nutrients, particularly phosphorus, which promotes root development. Here's how to do it:

    • After planting your cedars, apply a small handful of bonemeal fertilizer in the planting hole before backfilling with soil. This will provide your cedars with essential nutrients right from the beginning, encouraging healthy root growth.
  2. Future Seasons, Specifically in the Spring:

    Fertilizing your emerald cedars in subsequent seasons, particularly in the spring, is essential to support their annual growth and maintain their vibrant green color. When choosing a fertilizer for this purpose, opt for a granular product with a high first number on the label. This high number indicates a significant nitrogen content, which is crucial for promoting green foliage and overall growth.

    • In early spring, typically around April or May, apply the granular fertilizer evenly around the base of each cedar. Follow the manufacturer's instructions regarding the specific amount to use, as this may vary depending on the product.

    • After fertilizing, it's essential to water your cedars frequently. Fertilizer can heat up the roots, and adequate moisture helps to mitigate any potential stress on the tree.

Choosing the Right Fertilizer:

Selecting the appropriate fertilizer is essential for the health of your emerald cedars. Here's what to consider:

  1. Balanced Fertilizer for Planting:

    Bonemeal is an excellent choice when planting emerald cedars. It provides a well-rounded mix of essential nutrients, including phosphorus, which aids in root development. The balanced nature of bonemeal ensures your cedars get a healthy start in their new environment.

  2. High Nitrogen Fertilizer for Spring Application:

    In spring, when your cedars need a boost in growth and color, opt for a granular fertilizer with a high first number, indicating a significant nitrogen content. Nitrogen is crucial for promoting lush, green foliage and robust annual growth.

Application Tips:

When applying fertilizer to your emerald cedars, follow these best practices:

  • Distribute the fertilizer evenly around the base of each cedar.
  • Avoid direct contact between the fertilizer and the tree's trunk to prevent potential burn or damage.
  • Water your cedars thoroughly after applying fertilizer to help it penetrate the soil and activate the nutrients.


Fertilizing your emerald cedars in Ontario is a key factor in ensuring their year-round health and beauty. By applying a balanced fertilizer like bonemeal during planting and using a high-nitrogen granular fertilizer in the spring, you'll support healthy root development, vibrant foliage, and robust annual growth. Remember to follow the recommended guidelines for each fertilizer and maintain consistent watering practices, especially after fertilization, to help your emerald cedars thrive and grace your landscape with their lush greenery for years to come.