Varieties
Spruce refers to the Picea genus of plants, which includes 35 separate species. While the majority of these coniferous tree species have a fairly unremarkable average growth rate (between 6 inches and 11 inches per year), the Sitka spruce (Picea sitchensis), Norway spruce (Picea abies) and Colorado blue spruce (Picea pungens glauca) are renowned for their extraordinarily fast rates of growth.
Top Growth Rates
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The Sitka spruce dwarfs its cousins in maximum attainable height and rate of growth. During its 500-year life, a Sitka spruce will reach between 160 and 220 feet, with 60-inches-per-year growth rate until it reaches maturity. Coming in second with an average growth rate of 30 inches annually, the Norway spruce has an impressive yet manageable height between 40 and 60 feet. With a branch spread of 25 feet across, landscape designers will often arrange Norway spruces to provide privacy and wind blockage for houses on larger lots. While the growth rate for the Colorado blue spruce (13 inches per year) is slower than that of the Norway spruce, the former reaches a soaring 90 to 135 feet in height.
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Factors That Limit Growth
Spruces need space. At maturity, these three species have massive branch widths, ranging from 20 to 30 feet across. If spruces are planted too close together, root problems arise that lead to blight in the lower limbs. Likewise, immature spruces grow best in direct sunlight, so try to avoid planting them near taller, mature trees.
Spruces also are vulnerable to drought. In hot, dry weather, the young trees need to be watered at least once a week. Conversely, spruces' root systems need good drainage to thrive; planting them in a sandy or clay soil helps prevent puddles from building up.
A number of parasites target spruce trees, namely the spruce budworm and spider mite. In addition to slowing or stopping vertical growth, these pests can cause lower limbs to die and ruin the tree's symmetry. Fortunately, most arborists offer convenient and affordable spray treatment services to eliminate these pests on an annual basis.