Steadfast in cold winters, wind and drought, the white spruce (Picea glauca) grows 40 to 60 feet tall and 10 to 20 feet wide at maturity. Best suited for cold winter regions with cool summers, it makes a nice specimen tree, windbreak or linear hedgerow in USDA hardiness zones 2 through 5, perhaps in the colder parts of zone 6, as well. It does not cope with compacted soils or urban air and water pollution.
To develop into an uniform, well-branched and evenly-needled tree, locate a spot on your property where a white spruce receives at least eight hours of direct sunlight daily. Too much shading from nearby buildings or trees causes sparse branching and reduced foliage on twigs. White spruce's ideal soil conditions include an acidic to neutral soil pH (5.5 to 7.0) and a sandy or loamy soil rich in organic matter. The key is a well-draining soil that is not compacted or heavy. Clay or heavy loam soils need coarse bits of organic matter and grit incorporated for improved water drainage and porosity. Although drought tolerant, the white spruce grows better if the soil remains evenly moist across the growing season.
Plant a white spruce at least 5 to 10 feet away from shrubs and perennials in the garden so that when the spruce grows tall it is now overly crowded or shaded by nearby garden plants. Site the spruce at least 10 to 15 feet away from large, established shade trees or buildings. Planting a clustered grove of spruce trees creates a lush, dense matrix of branches edged in needles; shaded interior branches lose their needles but are rarely seen. For a cluster, plant trees 10 to 12 feet apart. To make an impenetrable windbreak or hedgerow, plant white spruce trees 8 to 15 feet apart. The closer the trees are planted, the more quickly their branches will grow into each other to block wind or views.
While container-grown spruce trees may be planted anytime of year when the soil is workable and not frozen, the best for planting is the very late summer or early autumn. Since white spruce grows in regions with very cold winters, gardeners in zones 2 through 4 should plant these trees in early spring to allow for as much new root growth as possible before the onset of winter.
Measure the size of the root ball of the white spruce. Dig the planting hole the same depth as the root ball, but two to three times as wide. Do not add soil amendments or fertilizers to the soil placed back around the tree once positioned in the planting hole. After the hole is filled, create a low berm around the tree to act as a catch basin for irrigation water. Keep the root ball of the planted tree well-watered for the first six months so that the soil remains moist, not soggy. Consider placing a 3-to-4 inch layer of organic mulch over the root zone of the planting spruce to conserve moisture and deter weeds. Extend the mulch outwards 2 feet beyond the the edge of the branches.
- University of Connecticut: Picea Glauca
- The United States National Arboretum: Conifer Questions and Answers
- "Dirr's Hardy Trees and Shrubs"; Michael A. Dirr; 1997
- Photo Credit spruce image by mzolna from Fotolia.com
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