The Emerald Green Arborvitae (Thuja occidentalis ‘Emerald Green’) is a popular evergreen used for dense hedges and privacy screens. It is prized for its naturally narrow, pyramidal shape and vibrant, year-round green foliage. While generally low-maintenance, timed fertilization is beneficial for maintaining color, supporting dense growth, and ensuring long-term health. A calculated feeding schedule helps the plant withstand environmental stresses and achieve its maximum growth potential.
Determining the Right Time to Fertilize
The optimal time to fertilize established Emerald Green Arborvitae aligns with the plant’s natural growth cycle. The primary feeding window is in late winter or early spring, just before the first flush of new growth begins. Applying fertilizer at this point ensures nutrients are available when the plant is actively expanding its foliage and root system.
A single application of a slow-release product in the spring is often sufficient for the entire growing season. A lighter, secondary feeding can be provided in early summer to support continued growth. Completely avoid fertilizing in late summer or fall, as this stimulates new, tender growth. This growth cannot survive freezing temperatures, making the plant susceptible to winter injury.
Established, healthy arborvitae may not require annual fertilization, especially in rich soil. Fertilize only every two to three years, or when the plant shows signs of nutrient deficiency, such as sparse foliage or dull color. Over-fertilizing can cause root burn or excessive, weak growth.
Selecting the Appropriate Fertilizer Type
Emerald Green Arborvitae needs emphasize nitrogen, which promotes deep green color and lush foliage density. The most suitable product is a balanced, slow-release granular fertilizer formulated for evergreens. Look for a blend where Nitrogen (N) is equal to or slightly higher than the Phosphorus (P) and Potassium (K) components, such as a 10-10-10, 12-6-4, or 20-10-10 ratio.
The slow-release formulation is recommended because it provides a steady supply of nutrients over several months. This gradual feeding minimizes the risk of fertilizer burn to the shallow root system, a common issue with quick-release synthetic products. Evergreens often benefit from a product containing at least 50% slow-release nitrogen.
Micronutrient deficiencies can sometimes be a concern. If the foliage exhibits persistent browning or yellowing unrelated to watering or winter damage, it may indicate a lack of micronutrients like iron or magnesium. In these cases, a targeted supplement may be necessary, but a regular complete NPK fertilizer addresses general health needs.
Application Techniques and Methods
For established arborvitae, granular fertilizer application must ensure effective nutrient delivery while preventing chemical burn. Always consult the product label for the recommended dosage, typically calculated based on the plant’s height or the area beneath the canopy. Using the correct amount is crucial to avoid over-fertilization.
Spread the fertilizer uniformly across the root zone, extending from the trunk outward to the drip line (beneath the outermost branches). This area contains the majority of the active feeder roots. Keep the granular fertilizer several inches away from the trunk or the immediate base of the plant to prevent direct contact and burning of the bark and main roots.
After broadcasting the granules, thoroughly water the area to activate the fertilizer. Water dissolves the nutrient pellets, allowing them to move into the soil for root absorption. Watering also prevents the concentration of salts in the soil, which could otherwise draw moisture out of the roots and cause damage.
Fertilizing Newly Planted Arborvitae
Newly planted Emerald Green Arborvitae require a cautious approach to fertilization, differing significantly from established specimens. During the first six to twelve months, the plant’s energy is dedicated solely to establishing a stable root system. Applying strong fertilizer during this phase can hinder root growth and potentially cause fertilizer burn to the young roots.
The focus for new plants should be on providing consistent moisture and protecting the root zone, not forcing top growth with nutrients. After the plant completes its first full growing season, a very light feeding can be considered. This initial feeding should be a diluted, low-concentration product, such as a liquid root stimulator or a mild fertilizer applied at half the recommended rate.
The most effective way to support a newly planted arborvitae is through proper soil preparation at planting time. Using a soil amendment like compost or a specialized acid-loving plant mix provides a gentle, slow release of organic nutrients without the risk of burning. After the first year, the plant can be gradually transitioned to a standard evergreen fertilizer schedule.