Picea glauca

White Spruce

Picea glauca, White Spruce

White Spruce, BWCA
Photo © by Earl J.S. Rook

Flora, fauna, earth, and sky...
The natural history of the northwoods


Name:

  • Picea, from the Latin for the the Scotch Pine, Pinus silvestris
  • glauca, from the Greek, glaukos (glaukos), "bright, sparkling, gleaming; grayish, bluish-green"
  • Common Name from the waxy white layer on the needles.
  • Other common names include Western White Spruce, Canadian Spruce, Alberta Spruce, Alberta White Spruce, Black Hills Spruce, Skunk Spruce, Cat Spruce, Porsild Spruce, Schimmel-Fichte (Ger), Hvítgreni (Is)

Taxonomy:

  • Kingdom Plantae, the Plants
    • Division Coniferophyta, the Conifers
      • Class Pinopsida
        • Order Pinales
          • Family Pinaceae, the Pines, Spruce, and Firs
            • Genus Picea - the Spruce, about 30 species from cool, temperate regions of the northern hemisphere, 7 native to North America.
  • Taxonomic Serial Number: 183295
  • Also known as Picea albertiana, Picea canadensis, Picea canadensis glauca, Pinus glauca
  • Species widely distributed across northern North America, exhibiting considerable geographic variation.
  • Natural hybridization between species of Picea is common. Although rare, White and Black Spruce (Picea mariana) hybrids, known as Rosendahl Spruce, have been found in northeastern Minnesota and other areas.

Description:

  • A medium-sized native conifer with a narrow, spirelike crown, to 100' or more.
  • Leaves stiff, 4-sided blue-green needles, ¾" long.
  • Stem
    • Trunk long and straight, to 24"-36" in diameter.
    • Branches self-pruning in dense stands, with crown eventually reduced to upper half of tree.
    • Bark on mature trees thin, usually less than 0.3" thick, scaly or smooth, light grey brown.
  • Roots generally descend 3'-4'; taproots and sinker roots to 10'. On northern sites, large roots usually within 6" of the mineral soil surface.
  • Fruit a light brown, oval cone, 2" long, pendant in branches of upper crown.

Identification:

  • Identifiable as a spruce by its stiff, 4-sided needles.
  • Distinguished from true firs, such as Balsam (Abies balsamea), in having pendulous cones, persistent woody leaf-bases, and four-angled needles, scattered and pointing in every direction; from Black Spruce (Picea mariana) in having longer needles, larger and more elongated cones, and a preference for upland areas.
  • Field Marks
    • Short, stiff, 4-sided evergreen needles
    • Conical form

Distribution:

  • Transcontinental; Newfoundland and Labrador along the tree line to Alaska, south to British Columbia, NW Montana, east to Michigan, New York, and Maine. Isolated population in the Black Hills.

Habitat:

  • Boreal forests, coniferous and mixed coniferous-hardwood forests; pure stands not widespead.
  • Soil: grows well on loams, silt loams, and clays, but rather poorly on sandy soils. Somewhat demanding, often restricted to sites with well-drained, mineral soils, mostly acid, with a pH of 4.0-5.5 Grows poorly on sites with high water tables.
  • Long-lived climax species that codominates or forms a significant part of the vegetation in mixed stands with Balsam Fir (Abies balsamea), and Black Spruce (Picea mariana). Gradually replaces pine, aspen, birch, and/or poplar on well-drained sites; less frequently an early successional species, forming pure stands or mixing with hardwoods immediately after fire.
  • Following stand destroying fires, dense stands of aspen, birch, and/or poplar tend to develop quickly, and these successional species are often scattered throughout all but the oldest white spruce stands. White Spruce seedlings establish under these hardwoods, develop and grow slowly, and eventually replace them. White Spruce/Aspen, White Spruce/Birch, and White Spruce/Balsam Poplar are common mid-successional communities that, with the continued absence of fire, will gradually be replaced by essentially pure stands of White Spruce.
  • Pests and diseases: Most common are needle and stem rusts, root diseases, trunk rots, mistletoe (Arceuthobium pusillum), bark beetles, wood-boring insects, weevils, Spruce Budworm, and Yellowheaded Spruce Sawfly.

Fire:

  • Easily killed by fire, its thin bark little protection for the cambium, and the shallow roots susceptible to soil heating. Surface fires can burn deep into litter and duff, charring or consuming roots 8"-9" in diameter.
  • Surface fires often spread to crowns because the highly flammable fine fuels concentrated under the trees often produce flames that reach the low-growing, flammable, lichen-draped branches.
  • Seeds have little or no endosperm to protect the embryo from high temperatures and are usually killed by fire on the ground. Cones may not be destroyed, but immature seeds will not ripen on fire-killed trees.
  • Relies on wind-dispersed seed to colonize burned sites. Not adapted to colonize large burns because most fires in boreal regions occur in the summer before seeds are mature, and seeds in cones on surviving trees are dispersed over relatively short distances. Fire-killed trees generally do not contribute to seedfall; seed for colonizing burns must come from nearby surviving trees. Because seeds in trees are mature and ready for dispersal by fall, white spruce can quickly invade areas after fall burns, especially during good seed crop years.
  • Under most circumstances, it can rapidly invade burned sites only when fire consumes the organic layer exposing mineral soil and when surviving trees provide a seed source. Frequent fires can eliminate White Spruce from an area because it does not produce seed in quantity until it is 30 years old or older.

Associates:

  • Trees: Balsam Fir (Abies balsamea), Sugar Maple (Acer saccharum), Yellow Birch (Betula alleghaniensis), Paper Birch (Betula papyrifera), Black Spruce (Picea mariana), Quaking Aspen (Populus tremuloides), White Cedar (Thuja occidentalis),
  • Shrubs: Moose Maple (Acer spicatum), Beaked Hazel (Corylus cornuta), Bunchberry (Cornus canadensis), Low Bush Honeysuckle (Diervilla lonicera), Twinflower (Linnaea borealis), Dewberry (Rubus flagellaris)
  • Herbs: Wild Sarsaparilla (Aralia nudicaulis), Large Leaf Aster (Aster macrophyllus), Blue Bead Lily (Clintonia borealis), Canada Mayflower (Maianthemum canadense), Sweet Bedstraw (Galium), Rose Twisted Stalk (Streptopus rosea), Starflower (Trientalis borealis)
  • Ground Covers: Dicranum Mosses, (Dicranum spp.), Ground Pine Clubmoss (Lycopodiumobscurum), Schreber's Feathermoss (Pleurozium schreberi)
  • Mammals
    • Palatability low for moose and deer
    • Snowshoe hares sometimes feed heavily on saplings and seedlings
    • Mice, voles, shrews, and chipmunks consume large quantities of seeds off the ground. Mice and voles eat the seedlings.
    • Red squirrels clip twigs and feed on vegetative and reproductive buds in the spring. Consumption of leaders and the ends of upper branches by red squirrels tends to be greatest during poor cone crop years. Seed a primary food of red squirrels, which prefer it over Black Spruce seed. Seeds are nutritious and a good energy source for red squirrels which can survive the winter on a diet consisting entirely of White Spruce seeds. White Spruce habitats are favored by red squirrels because of the highly palatable seeds; squirrel density is much greater in White Spruce stands than Black Spruce stands. Red squirrels are so dependent that population density is directly related to seed crop cycles.
  • Birds:
    • Spruce grouse feed entirely on spruce needles during winter.
    • Numerous seed-eating birds feed on seed.
    • Chickadees, nuthatches, crossbills, and pine siskin extract seeds from open spruce cones and eat seeds off the ground

History:

  • During the last Ice Age, vast White Spruce forests covered the Great Plains in a broad, transcontinental band, just south of the windswept tundra that bordered the great ice sheets. The premier pioneering tree on de-glaciated lands and the earliest species to follow the retreating ice northward, reaching northeastern Minnesota about 13,000 years ago.

Uses:

  • Wood light, straight-grained, and resilient; creamy white or straw-colored, with little visible difference between heartwood and sapwood. It dries easily, with moderate shrinkage, and remains stable after drying. Specific Gravity .33 green to .45 dry. Easily worked, it is moderately light in weight and moderately strong, stiff, tough, and hard with a straight, even grain.
  • Important commercially for pulpwood and construction lumber. Also used for specialty items such as sounding boards, paddles and oars, cabinets, boxes, and food containers.

Reproduction:

  • Reproduces by seed and vegetatively by layering.
  • Seed Production begins at 4 years of age but generally not in quantity until 30 years or more. Good to excellent seed crops every 2-6 years on good sites, but in many areas, only every 10-12 years. In natural stands cone production occurs primarily on dominant and codominant trees, with only sporadic production smaller trees. Seeds are about 1/8" long, with a 1/4"-1/3" wing.
  • Seed Dispersal by wind, most falling within about 300' of source, but seeds have been found as far as 1,300' away. Seeds found considerable distances from a source probably travel over crusted snow. Red squirrels also disperse seeds. White Spruce reproduction common at squirrel middens. Following dispersal, cones remain on tree for 1 - 2 years.
  • Seed Loss by red squirrel predation can reduce cone crops significantly, especially during poor or medium cone crop years. Insects also reduce seed yields, especially Spruce Cone Maggot, Fir Cone Worm, and Spruce Seed Moth. Following dispersal, small mammals consume considerable amounts of seed off the ground.
  • Seed Viability only 1-2 years. Under natural conditions, seeds overwinter under snow and germinate in the spring or summer when there is adequate moisture and soil temperatures have warmed.
  • Germination 50%-70%.
  • Seedling establishment best on mineral soil; may also establish on shallow organic seedbeds, but rarely where organic layers exceed 2"-3". Frequently found on rotten wood. Seedlings grow best in full sunlight, but tolerate low light, and can endure many years of shade. First-year seedlings are normally less than 1" tall, and less than 20" after 4-6 years.
  • Layering almost exclusive means of reproduction at northern treeline, where seed viability is low and seedlings are rare or absent. Layering also occurs farther south when the lower branches touch the ground and become covered with moss, litter, or soil.

Propagation:

  • Requires moist, cool stratification for 60 - 90 days to break dormancy.
  • Readily propagated by rooted cuttings

Cultivation:

  • Hardy to USDA Zone 3 (average minimum annual temperature -40ºF)
  • Cultural Requirements
    • Full sun
    • Well drained soil, pH 4.5 - 7.5
    • Medium to dry moisture
  • Size 20'-30'W x 100'H
  • Cultivars include:
    • "Alberta Spruce", a fine-textured, conical dwarf. Highly susceptible to winter burn.
    • "Black Hills Spruce", a sub-species (Picea glauca densata) highly regarded for landscape use in the upper Midwest.
  • Cultivars and species available by mail order or at local nurseries.
  • Planted as an ornamental and used in shelterbelt plantings.

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Last updated on 4 March, 2006