Red Spruce Vs. Blue Spruce Trees

Foliage and Cones

• The needles of the red spruce are about one-half inch long and dark green in color. The foliage of the blue spruce is, by comparison, extremely showy. Its needles are up to 1.25 inches long and a bright gray-blue in color; the needles darken slightly with age and are particularly colorful on new growth. Blue spruce cones are about 3 inches long; they're bright green when they're young and turn to tan or brown as they mature. Red spruce cones are smaller, up to 2 inches long, and are green or purple when they're immature; they change to a reddish brown color as they mature.

Size and Shape

• Both red and blue spruce are relatively slow growers, taking decades to reach their full mature height. Red spruce can reach over 20 feet in height in 20 years, but it can take 60 years to reach its maximum height of about 60 feet. In its native habitat, the blue spruce is even larger, often reaching heights of up to 75 feet; in cultivation, however, it's typically much smaller, usually reaching only 30 to 50 feet. Red spruce is broadly pyramidal in shape; blue spruce can be pyramidal, too, but some specimens are more upright and columnar.

Growth Requirements

• Red spruce is hardy in U.S. Department of Agriculture hardiness zones 2 to 5; blue spruce is hardy in USDA zones 4a to 7b. Both species do best in full sun or partial shade, but they prefer cool climates. Both trees also like soil that is moist but well-drained, although blue spruce is moderately tolerant of dry soils and drought.

Pests

• Both red and blue spruce are vulnerable to insect pests such as the spruce budworm, the eastern spruce beetle and the eastern spruce gall adelgid. Aphids and spider mites can also be a problem. Both species are susceptible to fungus-caused needle cast, which results in defoliation, and blue spruce is also susceptible to cytospora canker.