Blue Spruce, Colorado Blue Spruce, or Green Spruce

(Pinaceae - Pine Family)

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• Form
  • large evergreen specimen tree
  • maturing at 50' tall by 20' wide as a general rule, but cultivars are often smaller, and the species form in the wild will grow much larger
  • upright pyramidal growth habit in youth and often maintaining this form through maturity, but sometimes with age becoming conical with the lower branches drooping
  • arrangement of the natural branching of this pyramidal tree (without early shearing for increased density) varies from irregular, open, and very bold, to distinctly and beautifully layered, to dense and merging as if a solid unit
  • slow growth rate

• Culture
  • full sun to partial sun
  • prefers a moist, acidic, well-drained soil in full sun, but can tolerate many adverse conditions, including dry soils, soils of various pH, and Winter salt spray
  • usually propagated by grafting cultivar cuttings onto seedling understock, but selected species forms are also propagated by seeds, for use as less expensive trees of mixed foliage color or as rootstock for grafting
  • Pine Family, with several pests, of which spider mites are the worst, causing an overall decline in the new growth during mid-Summer, and several diseases, of which needle cast and trunk canker are the worst
  • abundantly available, primarily in ball and burlap form but increasingly in container form
  • Blue Spruce is sometimes not sheared at the nursery in youth, since it is naturally dense even at a young age, but it is often lightly sheared to promote even more fullness at transplant age
  • an annual spray program for spider mites might be implemented in landscapes where Blue Spruce is either of specimen quality and age, or is planted in sufficient numbers in close proximity to warrant this annual financial investment
  • Blue Spruce is somewhat tolerant of Winter salt spray, with green-foliaged forms being less tolerant (since they have less coating of needle wax) than blue or blue-silver forms

• Foliage
  • evergreen needles to 1.25" long, very stiff and sharp, uniformly distributed around the stem, radiating perpendicular to the stem for a prickly effect and therefore painful to grasp with a bare hand, or to manuever at transplanting without the advantage of supplemental gloves
  • variants almost always have intense blue or silvery-blue foliage that is especially vibrant on new growth

• Flowers
  • ornamentally inconspicuous, concentrated in the upper one-third of mature trees, monoecious, with staminate flowers orange and in the leaf axils, and pistillate flowers green or pink-purple and on the stem termini

• Fruits
  • straight cones grow to about 3" long and are light green when immature, become brown or tan with maturity, and abscisce slowly from the ends of branches in the upper canopy

• Twigs
  • young twigs are light green to light blue and may emerge semi-pendulous, becoming straight and stiff by Summer
  • seasoned twigs are light brown with an orange cast, with raised needle scars on the older stems that have defoliated their needles

• Trunk
  • thick gray scales with age are often hidden by the lower branches and foliage, unless the tree is limbed up

• ID Summary
  • vibrant silver-blue, blue, or blue-green needles are the highlight and near-uniqueness of this stately, upright pyramidal evergreen tree (except for the natural green-foliaged species forms, known as Green Spruce in the nursery industry), widely planted as a specimen, focal point, or screen, with many cultivars selected for intense foliage color, compactness, or different growth habit
  • mature needles radiate straight out from the stem, are stiff, to 1.25" long, and are very sharp and prickly when grasped with a bare hand (as opposed to Norway Spruce, the other common landscape spruce, which has needles to 1" long that are generally angled forward on the stem, more slender, less stiff and sharp, and are relatively comfortable to grasp with a bare hand)
  • mature needles on the terminal leader are the same in appearance as those of the side branches (unlike Norway Spruce, where the needles of the leader are sparse and slightly curving around the stem)
  • on mature trees of Blue Spruce, there are no long "skirts" of pendulous branchlets hanging from the main horizontal branches, although the older, lower branches may themselves angle downward and appear semi-pendulous as entire branches

• Function
  • blue-foliaged cultivars are commonly utilized as a specimen or focal point evergreen tree in lawn centerpieces, at the maximum curvature of large foundation beds, and at entranceways
  • also improperly utilized at house foundations (where the tree will get much too large and eventually envelope portions of the house, gutter, and roof, unless a dwarf cultivar such as 'Backeri' is used)
  • also properly used as a visual screen (in row or group plantings between properties or at roadsides) or as a windbreak

• Texture
  • bold texture
  • thick density

• Assets
  • evergreen tree with a formal symmetrical pyramidal shape that branches to the ground, usually with stunning blue, blue-green, or silver-blue foliage
  • bold texture (created by its stiff needles, stiff stems, formal outline, and blue color, an unusual combination for a narrow-leaf evergreen)
  • very drought tolerant, Winter salt-spray tolerant, and cold-hardy (once established in the landscape for two or three years after transplanting)

• Liabilities
  • spruce spider mites will lead to a decline in both vigor and stress resistance of infested trees
  • a very common "mistake of good intentions" is to site a vibrantly-foliaged Blue Spruce as the front lawn centerpiece, or near the foundation of the house, where it is such a "loud" focal point that it distracts the eye from all other features in the landscape (however, if you own a shack for a home, maybe this is a good idea)
  • a row or group transplanting of seed-grown "Blue Spruce" trees, while less expensive than that of the same planting of a uniformly blue-foliaged cultivar, will exhibit a wide variation in green versus blue-green foliage that, side-by-side, will only look worse over time to the purchaser of this nursery stock (or put another way, you get what you pay for)
  • Blue Spruce cultivars are among the more expensive trees to buy, due to their high demand coupled with the extra growing time needed at nurseries for a saleable tree (cultivar grafting and the slow growth rate combine for a longer-than-average time growing in the field)
  • when a recent transplant is not regularly watered for at least the first year of root re-establishment, it can result in the death of the terminal leader, dieback of side branch tips, or death of the entire tree, even though established Blue Spruce are quite drought-tolerant

• Habitat
  • zones 2 to 7
  • native to the Rocky Mountain regions of the Western United States

• Alternates
  • narrowleaf evergreen trees with a formal appearance and some blue shade of color (Abies concolor 'Candicans', Picea omorika, Pinus flexilis glauca 'Vanderwolf's Pyramid', Pinus sylvestris 'Watereri', etc.)
  • pyramidal evergreen trees of green foliage (Picea abies, Pinus strobus, Pseudotsuga menziesii, etc.)

• Variants
  • many exist, selected for a combination of foliage color (green, green-blue, sky blue, silver-blue, etc.) and growth habit (normal pyramidal, wide pyramidal, columnar, weeping, prostrate, globed dwarf, open branching versus layered branching versus dense branching, etc.); a few of the most common are listed below:
  • Picea pungens - in the nursery trade (when everything is correctly and fully labeled), this is Green Spruce, which has a medium-green, green-gray, or green-blue shading of the foliage, being a mixture of seed-grown trees that display the genetic diversity of the species in terms of diverse foliage color (so always look before you buy, and compare); to 50' tall by 20' wide
  • Picea pungens glauca (sometimes listed as Picea pungens 'Glauca') - Blue Spruce - a large, catch-all grouping of foliage variants that are blue, bluish-green, or silvery-blue in color, prized for their alternative evergreen color in the landscape, which can be attributed to a thicker-than-normal waxy coating on the true-green needles, refracting sunlight and reflecting it back to the human eye in a blue wavelength
  • Picea pungens glauca 'Backeri' - the best upright pyramidal cultivar for use at the foundation of a house, to 12' tall by 6' wide, with blue foliage
  • Picea pungens glauca 'Bizon' - a newly-released cultivar (also known as 'Bizon Blue') that has rapidly become very popular and in high demand, known for its intensely blue to blue-silver foliage color, and even more dense foliage, highly symmetrical outline, and straight central leader than is normal, to 40' tall by 15' wide
  • Picea pungens glauca 'Blue Totem' - a true "totem pole" vertical accent in the landscape, to 15' tall by 3' wide, having blue-green needles on dense, stiffly ascending branches
  • Picea pungens glauca 'Globosa' - a true dwarf specimen shrub, commonly sold as a "low-graft" when 1' tall by 2' wide, and slowly maturing to 3' tall by 5' wide while maintaining its flattop shape, but also sold as a grafted "standard" on a 1', 2', 3', or 4' "trunk"; very nice as a focal point accent that can either be prominently displayed, or hidden from other areas of the landscape so as not to constantly distract the eye
  • Picea pungens glauca 'Hoopsii' - perhaps the standard cultivar by which all other Blue Spruce are judged, maturing at about 40' tall by 15' wide, having blue-white foliage, slightly irregular and open in growth habit in youth, but assuming the normal tight pyramidal growth habit by about 15 years of age

• Translation
  • Picea is derived from the Latin word pix, or pitch, referring to the resin its bark contains.
  • pungens translates as "sharp-pointed," referring to the needles.
  • glauca translates as "glaucous", referring to the bluish-colored needles of most cultivars.

• Purpose
  • Blue Spruce is the most common blue-foliaged evergreen tree in landscapes, with many cultivars that differ in size, growth habit, and foliage color intensity.

• Summary
  • Picea pungens is a stately pyramidal evergreen tree that serves as a bold focal point in the landscape, especially with the numerous silvery-blue, blue-green, or sky-blue foliaged cultivars.