Growing nicely in USDA Hardiness Zones 6 through 9, the blue Atlas cedar is a magnificent evergreen tree of large proportions. Its short needles are silvery blue to powdery white in color, often contrasting other mundanely green plants in a large landscape. The least cold-hardy of all Cedrus species, it is more tolerant of heat and dry soil than others.
The blue Atlas cedar is a gymnosperm, or non-flowering plant, as well as a conifer, which is a plant that produces cones. Closely related to pines, it is a member of the pine family, Pinaceae. It is also a true cedar, grouped into the botanical genus of Cedrus. There is some disagreement among botanical taxonomists as to the Atlas cedar's appropriate botanical name, but it is either listed as Cedrus atlantica or Cedrus libani subspecies atlantica. The blue Atlas cedar is a naturally-occurring blue foliage form, and may be seen written as Cedrus atlantica forma glauca.
Both the Atlas cedar and the blue form of Atlas cedar are native to the well-draining soils of the Atlas Mountains of Morocco and Algeria in northwestern Africa. Although this region is arid, this species is tolerant of more humid regions as long as soil is well-draining.
Growing most often to heights of 40 to 60 feet, the blue Atlas cedar can tower over 100 feet on very old specimens. It has a broad, spreading canopy of branches that is 30 to 40 feet in spread. When a young tree, it is irregular and gangly with few branches and looking like a pyramid. The bark is grayish and vertically cracked.
The leaves are short, linear needles that are powdery silver-blue, nearly silver white when first emerging from buds. The leaves are evergreen, but persist for two to four years before dropped and being replaced. They occur in clustered tufts of 30 to 45 needles on short spurs along the branches. In early autumn, male and female cones appear on different branches on the tree. The male cones shed pollen and is carried by the wind to nearby female cones. The fertilized female cones persist on the tree, taking two years to fully mature, turn brown and break apart to release the seeds.
Because of its immense size at maturity and striking foliage color and texture, a blue Atlas cedar is grown as an ornamental lawn tree. It is grown as a solitary plant, or specimen, in a spacious landscape so that the tree's natural form and beauty can be best appreciated. One grand use is growing it beside the shores of a pond or lake where its cascading and tiered branches are particularly striking.
Dwarf and weeping varieties have been selected over the years, allowing different forms and sizes of blue Atlas cedar to be enjoyed in smaller landscapes where the regular species would grow too large. Most popular is perhaps selection Glauca Pendula, the weeping blue Atlas cedar. This tree is shorter than the species but wide-growing, with fewer, pendulous branches.