Picea glauca aka Dwarf Alberta Spruce

White spruce, Picea glauca, is an evergreen conifer in the pine family. Its native range runs from Alaska across Canada to Labrador. It also extends into the northern United States, south to Montana, Minnesota and New York. It often grows at the arctic tree line. Older references list it as Picea alba, and some gardeners know it as skunk spruce or Canadian spruce.

In gardens the tree reaches 40 to 60 feet (12 to 18 m) tall and 10 to 20 feet (3 to 6 m) wide. Wild trees can reach 80 to 100 feet (24 to 30 m). The RHS gives an upper limit of about 165 feet (50 m). The crown is a narrow cone with branches held level. Young trees are dense, but the canopy opens out with age. Growth is moderate. A tree may take 20 to 50 years to reach full size.

The needles are short, stiff and sharp-tipped. They are four-sided in cross section and range from green to blue-green. Pale bands of stomata give them a waxy, glaucous look. Each needle lasts three to four years. Crushed needles give off a sharp smell that people compare to skunk or cat urine. Young shoots are grey or yellowish brown. Older bark is ash-grey to light brown and flakes away to show a silvery layer beneath.

The tree bears male and female cones on the same plant, but they have little ornamental value. The seed cones are slim cylinders up to about 2.5 inches (6 cm) long. They cluster near the branch tips. They start pale green and ripen to light brown. Their thin scales have smooth, rounded edges.

White spruce likes full sun but will take some shade. It does best in deep, moist, well-drained soil that is neutral to acid. It copes with clay, loam or sand, and one source favours sandy ground. The tree is very cold hardy, down to USDA zone 2 and RHS rating H7. It prefers cool climates. It stands up well to wind, heat, cold, drought and crowding. Sources disagree on salt and city conditions. One praises its use by the sea, while another says pollution and salt spray harm it. It needs no pruning, and large trees move well.

Gardeners plant it as a specimen, a hedge, a screen or a windbreak. It also works in mass plantings and makes a popular Christmas tree. Deer tend to leave it alone. The timber goes into lumber and pulp. Native North American peoples made string from the long roots and drew pitch, tannin and dye from the tree.

The tree has few serious problems, but several pests can attack it. Eastern spruce gall adelgid leaves ugly galls. Spider mites are common, and repeated outbreaks can do real damage. Spruce budworm, yellow-headed spruce sawfly, spruce beetle and conifer aphid may also appear. Disease risks include rusts, canker, root rot and honey fungus.

No hazards are recorded for white spruce. Several parts are edible, though mostly as survival food. Young male cones flavour food, and roasted immature female cones taste sweet. The inner bark can be dried and ground into flour. Native peoples used the bark and cones to treat coughs, colds and urinary complaints.