Canadian or glaucous spruce

Synonyms: Canadian spruce, glaucous spruce, white spruce, Abies alba, Abies alba (Aiton) Michx. nom. illeg., Abies arctica A.Murray bis, Abies canadensis Mill., Abies coerulea Lodd. ex J.Forbes, Abies laxa (Münchh.) K.Koch, Abies virescens R.Hinterh. & J.Hinterh., Picea acutissima Beissn., Picea alba (Aiton), Picea canadensis (Mill.) Britton, Sterns & Poggenb. nom. inval., Picea coerulea (Lodd. ex J.Forbes), Picea laxa Sarg., Picea tschugatskoyae Carrière nom. inval., Pinus alba Aiton, Pinus canadensis Du Roi nom. illeg., Pinus coerulea Lodd. ex Loudon nom. inval., Pinus glauca Moench, Pinus laxa (Münchh.) Ehrh., Pinus tetragona Moench, Pinus virescens Neilr. nom. inval.

Canadian or glaucous spruce (Picea glauca) – a species of evergreen trees in the genus Spruce (Picea) of the family Pinaceae. Native to North America. Cultivated in Europe since 1700.

Occurs in North America from Alaska to Newfoundland in the east. In the north it reaches the 64th parallel, where it is limited by the forest-tundra; in the south it extends to the states of Montana and Michigan, Maine, Wisconsin. Also found in the Dakotas and Wyoming. Grows in the forest zone, along rivers and lakes, and forms pure and mixed stands. Ascends mountains up to 1500 m above sea level. Lifespan – 300-500 years.

Individuals of the species are medium-height trees 15-20 (40) m tall, the trunk reaches 1 m in diameter. A slow-growing tree, annual increment reaches 15-30 cm. The crown is dense, compact, regular, conical, narrowly conical, in old trees - cylindrical. In youth the branches are directed upwards, in more mature trees they are flat and pendulous. Bark scaly or smooth, ash-brown in color. Young shoots glabrous, yellowish-brown or whitish-light-brown. Buds almost spherical, up to 6 mm long and 4-5 mm wide, not resinous. Bud scales light brown, glossy, bluntly ovoid.

Needles rhombic in cross-section, 8-18 mm long and 1.5 mm wide, stiff, densely arranged, slightly curved, bluish-green above, bluish-white below, when crushed emit an aroma similar to blackcurrant. Remain on the tree 5-7 (11) years.

Pollinates annually and abundantly, starting from 8 years of age.

Cones ovoid-cylindrical, 3-6 (7) cm long and 1.5-2.5 cm in diameter, light green before ripening, later becoming light brown, located not only at the top of the tree. Seed scales elastic and thin, obovate-cuneate, with an entire upper margin. Seeds 2-3 mm in length, light brown, winged. The wing is orange-brown, three times longer than the seed.

Seeds ripen in mid-September. Seed viability 71%.

Cultivars: currently more than 20 ornamental forms are known. The most popular among them: 'Alberta Globe', var. albertiana 'Blue Wonder', 'Coerulea', 'Conica', 'Daisy’s White', 'Echiniformis', 'Gnom', 'Gracilis Compacta', 'Laurin', 'Lilliput', 'Nana', 'Pendula', 'Sanders Blue', 'Zucerhut'.

Hardiness zone: 3-7b.

Site: less sensitive to smoke and gases than the European spruce. Can tolerate considerable shade, but a beautiful, low-hanging, dense and symmetrical crown forms only in sunny and open locations. Prefers moist and fertile soil, light- or medium-loamy. Does not tolerate dry sandy loam. The topsoil should be well permeable so that roots receive adequate air supply. Drought resistance is moderate.

Planting: tolerates transplanting well. Planting hole size: 70x70x70 cm. Soil mix: turf soil, humus and sand in a ratio of 3:2:1.

Care: the trunk circle is recommended to be periodically weeded and loosened, but not dug over. It is also advisable to mulch the trunk circle with peat or loose compost with subsequent incorporation. During dry periods regular watering is recommended, avoiding complete drying of the root-inhabited soil layer. Manuring with manure or compost can also be carried out. Most forms need protection from harsh spring sun.

Pruning: tolerates shaping and shearing well.

Diseases: Schütte, snow Schütte, fusariosis, stem and root rot, bark necrosis, canker (wound cancer), cone rust, spruce dieback.

Pests: Sikhote spruce aphid, red and yellow gall aphids, caterpillars of the nun moth, green spruce-elm adelgid, spruce needle-roller, spruce spider mite, spruce false scale, root aphid, conifer mealybugs, spruce sawfly, spruce bud sawfly, spruce moth, weevil, caterpillars of the spotted noctuid, dark gray inchworm and angular-winged conifer geometrid, cone moth, bark beetle (typograph), large spruce bark borer, black spruce longhorn beetle, spruce timberman.

Propagation: propagated by cuttings, which is best done in early June. Untreated winter cuttings do not root. For cuttings, take matured lower branches from the mother plant that do not exceed 10-12 cm in length. The cutting removed from the mother plant must have a "heel" (a small piece of older wood), otherwise the plant will quickly die. The lower part of the prepared cuttings should be treated with rooting stimulants. Plant cuttings to a depth of 2-2.5 cm. The substrate must not dry out during rooting, but overwatering is not recommended.

Uses: used in solitary and group plantings; dwarf forms are used to decorate rock gardens and rockeries. Can be used as a windbreak plant. Companions: Japanese spirea 'Goldflame' and 'Golden Princess', Thuja 'Danica', 'Aurea' and 'Globosa', Barberry (Berberis thunbergii), creeping juniper, creeping willows and groundcover perennials.