The Green Giant Arborvitae (Thuja plicata x standishii ‘Green Giant’) is a popular, fast-growing evergreen conifer used for creating dense privacy screens and hedges. This hybrid is prized for its rapid growth rate, often adding three to five feet per year, and its dense, rich green foliage. Although resilient and low-maintenance, providing the right nutrients is important for maintaining density and maximizing growth potential. Proper fertilization ensures the tree remains healthy, vigorous, and better equipped to resist environmental stress and minor pest issues.
Nutrient Requirements of Green Giant Arborvitae
The health and rapid growth of the Green Giant Arborvitae depend on a steady supply of specific macronutrients. Nitrogen (N) is important for evergreens because it directly supports the development of lush, dark green foliage and drives the vigorous growth rate. A deficiency in nitrogen often results in yellowing needles and stunted growth, especially in younger trees.
Phosphorus (P) is vital for strong root development and energy transfer within the plant, which is necessary for anchoring these large, fast-growing trees. Potassium (K) helps regulate water uptake, enhances hardiness, and improves resistance to drought, cold temperatures, and disease. A balanced approach to these three elements is necessary, though the specific ratio often favors foliage growth.
Before applying fertilizer, understanding the existing soil composition is beneficial. Green Giant Arborvitae thrive in well-drained soil with a slightly acidic to neutral pH, ideally ranging between 5.5 and 7.0. Testing the soil pH ensures that nutrients are readily available for the roots to absorb, as extreme pH levels can lock up abundant nutrients.
Selecting the Best Fertilizer Type and Ratio
The most effective fertilizer is typically a slow-release granular formulation designed for trees and shrubs. This type is preferred because it releases nutrients gradually over several months, providing a consistent food source that matches the tree’s steady growth cycle. This controlled release minimizes the risk of nutrient burn and prevents the sudden flushes of weak growth associated with fast-acting fertilizers.
A higher nitrogen content is recommended to support the lush, dense foliage. For established trees, a ratio that favors nitrogen, such as 3:1:1 or 4:1:2 (e.g., 16-5-9 or 18-5-12), is suggested to promote continued height and density. Younger or recently planted trees may benefit from a more balanced formula, such as 10-10-10, for the first few years to ensure robust root establishment alongside canopy growth.
Organic alternatives, such as composted manure or organic granular fertilizers like cottonseed meal, offer a gentle feeding option that improves soil structure. These materials release nutrients slowly as they decompose, which reduces the risk of burning and feeds beneficial soil microorganisms. Liquid fertilizers are not typically used for routine feeding but can quickly correct a minor nutrient deficiency in a struggling tree, providing an immediate but short-lived boost.
Optimal Timing and Application Techniques
The optimal time to fertilize Green Giant Arborvitae is in the early spring, just before the start of the new growing season. Applying fertilizer at this time ensures nutrients are available when the tree begins its most active period of growth. A single application of a slow-release product in early spring is usually sufficient for the entire year, supporting growth through summer.
Some growers apply a light follow-up application in early fall, typically around September, to help the tree store energy for the winter. However, strictly avoid fertilizing in late summer or late fall. Fertilizing too late can stimulate tender new growth vulnerable to early frost damage. Fertilization must be timed to allow any new growth to harden off before cold weather arrives.
The application technique is important for nutrient uptake and plant safety. Granular fertilizer should be spread evenly on the soil surface, starting a few inches away from the trunk and extending out to the tree’s drip line. The drip line is the area beneath the outermost branches, where the majority of the feeder roots are located.
The fertilizer must not be piled directly against the trunk or foliage, as this can cause severe chemical burn. After spreading the granules, lightly rake the fertilizer into the top inch of soil to prevent runoff. Then, water the area thoroughly. Deep watering immediately after application is necessary to dissolve the nutrients, activate the slow-release coating, and allow the roots to begin absorbing the feed.