Arborvitae, belonging to the Thuja genus, are widely used evergreen trees and shrubs valued for their dense, green foliage and ability to form effective screens or hedges. While generally low-maintenance, they thrive best when their specific nutritional needs are met. Proper fertilization helps maintain their vibrant green color, ensures robust growth, and supports overall plant health, especially where soil nutrients are depleted. A calculated feeding program helps these evergreens resist environmental stress.
Understanding Arborvitae Nutritional Requirements
Arborvitae require specific macronutrients and soil conditions to maintain their deep green appearance. Nitrogen (N) is the most important nutrient, directly supporting the dense foliage and rich color. Nitrogen deficiency is often the most common issue, as this water-soluble nutrient can leach quickly from the soil.
The soil’s pH level significantly influences nutrient absorption. Arborvitae prefer a slightly acidic environment, ideally with a pH range between 6.0 and 6.8. If the soil becomes too alkaline, it hinders the uptake of essential micronutrients like iron and manganese, leading to deficiency signs.
The most visible sign that an arborvitae needs feeding is the yellowing or browning of the foliage, known as chlorosis. Yellowing or bronzing branch tips, especially on older growth, often indicate a need for nitrogen or magnesium. Slowed growth and thin, sparse foliage are also general indicators that the plant is not receiving adequate nutrition and would benefit from a complete fertilizer.
Selecting the Best Fertilizer Formulas
The best fertilizer provides a steady, balanced supply of nutrients, often leaning slightly toward nitrogen. A complete fertilizer containing nitrogen (N), phosphorus (P), and potassium (K) is recommended unless a soil test indicates otherwise. Suitable N-P-K ratios include balanced formulas like 10-10-10 or 20-20-20, or formulas with a higher nitrogen component, such as 3-1-2 or 10-4-4.
Slow-release granular fertilizers are superior to quick-release liquid feeds, providing a sustained nutritional benefit. These granulated products dissolve slowly over several months, ensuring the plant receives a steady supply of food throughout the growing season. This slow delivery prevents the rapid growth spikes and potential root burn associated with a sudden high dose of nutrients from quick-release synthetic products.
Organic options, such as compost, aged manure, or organic granular feeds, offer another excellent way to provide nutrition. These materials not only add nutrients but also improve soil structure and foster a healthy microbial environment. While synthetic fertilizers offer precise nutrient ratios, organic sources feed the soil over a long period, which aligns well with the long-term needs of an evergreen.
Proper Timing and Application Techniques
The ideal time to fertilize arborvitae is in the early spring, just before the emergence of new growth. Applying fertilizer at this time ensures the nutrients are available when the plant is actively growing and can best utilize the food to develop new foliage. A single application of a slow-release fertilizer in spring is often sufficient to nourish the plant for the entire growing season.
A lighter second feeding may be applied in the early fall to help the plant store energy before winter, but application must strictly avoid late fall. Fertilizing too late in the season can promote a flush of tender new growth that lacks the necessary time to harden before the first frost, making it highly susceptible to winter damage.
When applying granular fertilizer, scatter it evenly across the soil surface, extending from the trunk out to the drip line (the outer edge of the branches). Keep the granules several inches away from the main trunk and stems to prevent chemical burn. After broadcasting the fertilizer, water the area deeply to help dissolve the granules and carry the nutrients down into the root zone. Avoid over-fertilization, as the excess salt can cause salt burn, resulting in browning foliage.