The genus Picea, commonly known as spruce trees, is a large group of evergreen conifers planted widely for both landscaping and commercial forestry. These trees are generally categorized as slow to moderate growers, but the rate at which they increase in height each year is highly dependent on the species chosen. Understanding spruce growth requires recognizing the significant variability within the genus. The growth rate changes not only between species but also based on the tree’s age and its surrounding environment.
Typical Growth Rates of Common Spruce Species
The growth rate is classified by the annual height increase once the tree is established, typically after the first year or two in the ground. Fastest-growing species often exceed two feet (24 inches) per year, while the slowest may only add a few inches. This annual measurement is most pronounced in young trees and slows as they mature and put more energy into girth.
Norway Spruce (Picea abies) is the fastest-growing common landscape spruce, often adding 2 to 3 feet (24 to 36 inches) of vertical growth annually. Under favorable conditions, this species can achieve up to 5 feet of new growth in a single year during its juvenile stage. This rapid growth makes it a popular choice for windbreaks and privacy screens.
The White Spruce (Picea glauca) exhibits a moderate growth rate, typically increasing in height by 13 to 24 inches each year. This species is a reliable performer across a wide range of climates.
In contrast, the popular Colorado Blue Spruce (Picea pungens) is a slow to moderate grower, typically adding between 8 and 15 inches annually. While a healthy young Blue Spruce may reach 2 feet per year in optimal conditions, a slower pace is more common.
Sitka Spruce (Picea sitchensis), though less common in general landscaping, is the largest spruce species and the fastest grower in commercial forestry settings. This tree can achieve vertical growth of up to 5 feet (60 inches) per year when planted in its preferred coastal, high-moisture environment. Species maintaining an annual growth rate of over 2 feet are considered fast, while those consistently below 1 foot are classified as slow growers.
Key Environmental Influences on Growth Speed
The maximum potential growth rate is a genetic trait, but the actual rate achieved is constrained by environmental conditions. Soil quality, moisture availability, and light exposure are the primary external factors dictating performance. Spruce trees require well-drained, consistently moist soil, as their root systems are susceptible to rot in waterlogged conditions.
The soil’s pH level affects nutrient uptake, with most spruces performing best in a slightly acidic to neutral range (5.5 to 7.5). Growth can slow if the soil becomes too alkaline, limiting the tree’s ability to absorb essential micronutrients. Most spruces also need a minimum of six hours of direct sunlight daily for robust growth.
Regional climate plays a significant role, especially for species like the Sitka Spruce, which relies on high atmospheric moisture for rapid growth. The growing season is triggered by temperature, with expansion beginning when daily average temperatures rise above 5°C. A lack of available water is a growth-limiting factor, particularly during peak summer, causing a premature slowdown if soil moisture drops too low.
Strategies for Encouraging Optimal Growth
To ensure a spruce reaches its maximum growth potential, careful management of its environment is necessary, especially during the first few years after planting. Proper establishment requires regular watering, which is important for newly planted trees during their first year. Applying a 2 to 4-inch layer of organic mulch around the base conserves soil moisture, regulates root temperature, and suppresses competing weeds.
Targeted fertilization can boost the growth rate of young or nutrient-deficient trees. Spruce trees benefit most from a high-nitrogen fertilizer (e.g., 20-20-20 or 10-8-6), applied in early spring before new buds break, or in the late fall. For newly transplanted trees, a high-phosphorus fertilizer may be applied during the first year to encourage strong root development, which is the foundation for future rapid height growth.
Pruning in the early stages should focus on maintenance and density rather than size control. If a denser appearance is desired, one-third to one-half of the new growth, called the “candle,” can be removed in the spring. This practice forces the tree to branch more heavily, creating a fuller canopy. Regular monitoring for competing vegetation and ensuring adequate space completes the strategy for optimal growth.