The most common blue evergreen tree or shrub in the landscape is the Colorado blue spruce (Picea pungens). The large native tree is found in the Western mountainous areas of the USA. The Colorado blue spruce thrives in U.S. Department of Agriculture plant hardiness zones 2 through 8. Many of these cultivated varieties, derived from the Colorado blue spruce, also develop well in these USDA zones.
Big Blue Spruce
The native Colorado blue spruce and its normal variation, Colorado blue spruce Glauca (P. pungens var. Glauca), can develop 50 to 80 feet in the landscape as well as taller in the wild. Most blue spruce varieties are smaller, even though the large ones. Moerheim (P. pungens “Moerheim”), Hoopsii (P. pungens “Hoopsii”) and also Iseli Fastigiata (P. pungens “Fastigiata”) are examples of large blue spruce varieties. Moerheim is a tree with dense foliage that reaches about 30 feet at maturity. It is a hardy, fast-growing tree with an irregular habit when young, becoming erect and pyramidal with age. Moerheim preserves its blue foliage throughout its growth phase. Possibly the strongest blue color is displayed by Hoopsii. It forms a neat upright tree of approximately 30 feet. Iseli Fastigiata also has great blue coloration and is very narrow with upward-pointing divisions, which makes a striking accent in the landscape.
Medium-Sized Blue Spruce
Medium-sized or semi-dwarf forms of Colorado blue spruce include Fat Albert (P. pungens “Fat Albert”) and Montgomery (P. pungens “Montgomery”). Fat Albert has glowing blue foliage and a squat, pyramidal shape. The tree is broad and rounded when young and will achieve 8 feet by 6 feet in 10 years following planting. Montgomery has a conical and globular shape with attractive silvery blue needles. It grows slowly, just 3 to 6 inches each year. After 10 years, Montgomery can reach 3 to 4 feet and a width of 3 feet.
Dwarf Blue Spruce
Dwarf Colorado blue spruce varieties have a tendency to get a globular form along with a slow growth habit. A good example of a dwarf variety is Glauca Globosa (P. pungens “Glauca Globosa”), which grows no more than 2 to 3 inches each year, eventually reaching a height of 2 or 3 feet. With time, it may become wider than tall and may develop one or more leaders, which should be pruned away to maintain its kind. Utilize neon blue spruces in rock gardens, mixed borders, as a low hedge or in containers. The shrubs are not fussy about the kind of soil, but prefer well-drained soil and a sunny or partially sunny location.
Prostrate Blue Spruce
The number Procumbens (P. pungens “Procumbens”), sometimes called “Prostrata,” is a low, spreading ground cover shrub. It grows 1 foot tall and also becomes 8 feet wide after 10 years. Procumbens is striking when used on slopes or when its silvery blue-green foliage spills over a rock wall.