Atlas cedar

Identification and origin

Cedrus atlantica belongs to the Pinaceae, the family of pines, firs and larches. It is native to the Atlas Mountains, from northern and central Morocco to northern Algeria. It has been introduced to many European countries, as well as Tunisia and the Canary Islands. Its classification is debated: some botanists treat it as a subspecies of cedar of Lebanon, but it is still widely known under its own name.

In cultivation the tree usually reaches 39.5–59 ft tall and 29.5–39.5 ft wide; in the wild it can reach 131 ft. It takes twenty to fifty years to reach full size. Young trees are conical, with a stiff, upright leader; with age, the top flattens and the large branches spread horizontally, without drooping at the tips.

• Needles: evergreen, short, stiff and pointed, roughly four-sided in cross-section, 1–1 in long. On short spur shoots they grow in tufts of ten to thirty; on long shoots they are borne singly. Their color ranges from green to blue-green or silvery blue. Young shoots are downy. A young cedar can look like a larch, but it keeps its needles all year, while a larch drops them in winter.
• Pollen cones: upright, about 2 in long, releasing clouds of yellow pollen in fall.
• Seed cones: upright on the branches and barrel-shaped, 2–3 in long, glossy light brown when ripe. They take two years to mature, then break apart on the tree to release the seeds.
• Bark: silvery gray to dark gray and fissured; with age it breaks into a pattern of rectangular plates.

There are many cultivars. ‘Glauca’, the blue atlas cedar, covers blue-foliaged selections, often picked from seedling populations; it is the most widely planted form. ‘Glauca Pendula’ has drooping branches with steel-blue needles; ‘Pendula’ is weeping; ‘Fastigiata’ is narrow and columnar; ‘Argentea’ has silvery-blue needles, and the rarer ‘Aurea’ has yellowish needles.

Light

Atlas cedar needs full sun, with at least six hours of direct sun a day, and tolerates some partial shade. It accepts east-, south- and west-facing sites, whether exposed or sheltered. As a bonsai, a spot in full sun all year suits it.

Watering

Once well established in the ground, the tree tolerates drought; it suffers far more from soil that stays soggy than from a dry summer.

In a container, this conifer from dry regions prefers a mix kept on the dry side rather than too wet. Let the surface dry before watering, then water thoroughly; in midsummer this can mean every day. Overwatering causes root rot. In winter, avoid a waterlogged root ball, which freezes more easily.

Potting mix

Atlas cedar tolerates a wide range of soils, whether sand, clay, loam or chalk, acidic or alkaline, as long as they drain well. It prefers deep, loamy soil that stays moist without standing water. In a container, use a very free-draining mix; for a bonsai, a conifer mix of equal parts akadama, pumice and lava rock works well.

Temperature

The species is hardy in USDA zones 6a to 9b and withstands winters of -4–5 °F in the ground. It does dislike strong, sweeping winds, so plant it out of wind corridors. Heavy snow can break its spreading branches.

In a container, protect the root ball from frost and cold wind; young plants need extra protection. The tree needs winter cold and cannot be grown indoors.

Repotting

In the ground, Atlas cedar is planted as a specimen tree, with 24–59 ft of open space: its spreading branches need plenty of room. Because it is highly flammable, keep it out of the defensible space around a house.

In a container or as a bonsai, repot a young tree every two years and an older one every three or four years, in spring before bud break or in fall; late summer, after the last flush of growth, also suits it well. Disturb the roots as little as possible: do not remove all the old soil at once, and prune roots only lightly, because cedars sometimes drop older needles after a rough repotting.

Pruning

In the garden, Atlas cedar needs no pruning.

As a bonsai, shorten twigs in early spring and pinch new shoots throughout the growing season, never cutting the needles. Save the removal of large branches for fall to limit resin bleeding. Wounds heal very slowly: instead of cutting flush, leave a stub to turn into deadwood.

Propagation

• Seed: the most common method. Sow in spring after moist cold stratification, for example three weeks at 32–34 °F.
• Grafting: used to reproduce cultivars.
• Cuttings: semi-hardwood cuttings are possible, but cuttings and air layers have a low success rate.

Common problems

One symptom can have several causes: needles that yellow or drop can come from overwatering, overly harsh repotting, a pest or a disease. Look at the tree and its conditions before treating.

• Pests: aphids, especially the conifer aphid, and pine needle scale.
• Diseases: root rot in soggy soil; honey fungus; the fungi Sirococcus and Pestalotia, which cause shoot blight and needle drop. Improve growing conditions and use a specific treatment if needed.
• Mechanical damage: branches broken by heavy snow or wind.

Overall, Atlas cedar causes few problems when planted in sun and free-draining soil.

Toxicity

No toxicity has been reported: Atlas cedar does not appear among the plants listed as toxic to dogs, cats and horses by veterinary references. Still, keep children and pets from chewing its needles, cones or resin.