If you love cedar trees and have a large space for growing one, an atlas cedar tree (Cedrus atlantica) is a fine ornamental choice. One of the true cedar trees, it takes its common name from its home region, the Atlas Mountains in northern Africa. It is an evergreen conifer with a pyramidal shape when young, but it develops spreading branches and becomes more flat-topped as it matures.
I. Appearance and Characteristics
Cedrus atlantica, the Atlas cedar, is a species of tree in the pine family Pinaceae, native to the Rif and Atlas Mountains of Morocco (Middle Atlas, High Atlas), and to the Tell Atlas in Algeria. A majority of the modern sources treat it as a distinct species Cedrus atlantica, but some sources consider it a subspecies of Lebanon cedar (C. libani subsp. atlantica).
Fully grown, Atlas cedar is a large coniferous evergreen tree, 30 to 35 m (98 to 115 ft) (rarely 40 m) tall, with a trunk diameter of 1.5 to 2 m (4.9 to 6.6 ft). It is very similar in all characters to the other varieties of Lebanon cedar; differences are hard to discern. The mean cone size tends to be somewhat smaller (although recorded to 12 cm, only rarely over 9 cm long, compared to up to 10 cm in C. brevifolia, and 12 cm in C. libani), though with considerable overlap (all can be as short as 6 cm). The Cedrus atlantica leaf length (10–25 mm) is similar to that of C. libani subsp. stenocoma, on average longer than C. brevifolia and shorter than C. libani subsp. libani, but again with considerable overlap.
Atlas cedar form forests on mountainsides at 1,170 to 2,200 m (3,840 to 7,220 ft), often in pure forests, or mixed with Algerian fir – Abies numidica, Juniperus oxycedrus, holm oak – Quercus ilex, and Acer opalus. These forests can provide habitat for the endangered Barbary macaque (Macaca sylvanus), a primate that had a prehistorically much wider distribution in northern Morocco and Algeria.
Currently, Morocco has the highest total surface of Atlas cedar in the world, and it forms vast forests in the humid zones of the country, around the Middle-Atlas range, the oriental and Northern High-Atlas range, and in the Western and Central Rif mountain range. The current total area is around 163,000 hectares, of which around 115,000 hectares (80%) are situated in the Middle-Atlas mountains. The species is in danger from human use, wood harvesting and fires. Data that go back to 1927 show a higher number of Atlas cedars (more than 150,000 hectares) in the Middle-Atlas mountains only. The Rif mountains had one of the largest cedar forests in the past, but forests nowadays are much smaller, 15% of the total cedar forests in Morocco. Recently massive reforestation campaigns have taken place in the region of Ifrane Province.
In Algeria, the Atlas cedar has been in significant decline. According to data from 1966 the species inhabited 23,000 hectares, forming forests around the Djurdjura Mountains in Kabylie and Aures Mountains. However, it is expected that it currently inhabits fewer than 15,000 hectares owing to extensive fires and human use.
II. How to Grow and Care
Sunlight
In order for the blue Atlas cedar to thrive, it’s best planted in a spot in your lawn or landscape that receives at least six to eight hours of full sun a day. This tree can withstand more shade when planted in areas of the country with warmer weather, though it should never be planted in full shade.
Temperature and Humidity
This is a tree suited only for the moderate conditions of USDA zones 6 to 9. Within this range, the blue Atlas cedar can handle a variety of temperature and humidity conditions. It’s a good idea to shelter young trees from exposure to strong winds, which can bend or break their limbs.
Watering
A newly-planted tree should be watered regularly. Water every week or so, keeping the soil moist but not soggy. Once established, atlas cedar is fairly drought tolerant, but in extremely hot and dry weather you should still water occasionally.
Soil
The blue Atlas cedar does best in well-drained, somewhat acidic soil, though it will happily tolerate neutral and slightly alkaline soils. That this tree should be planted in a spot that boasts a deep and wide swath of soil—its roots run deep, and its branches are quite expansive, so it will need room to grow or its size will suffer. Blue Atlas cedar can thrive in a variety of soil mixtures, including loamy, sandy, or clay, provided the soil doesn’t retain too much moisture.
Fertilizing
Atlas cedar doesn’t need a lot of fertilizer, but a small amount can help encourage growth. Every other year, fertilize your atlas cedar with a well-balanced fertilizer, like a 10-10-10 (N-P-K). It’s best to fertilize in the spring or early summer when the tree is putting on new growth.
Planting Instructions
To plant your atlas cedar, select a site with full sun or partial shade and dig a hole slightly larger than your tree’s pot or root ball. For best results, add some compost to the hole. Place your tree in and fill in around it, ensuring that the soil is at the same level as it was in the pot. Firmly pack soil around the roots and pack down the final layer with your feet. Water your atlas cedar in well.
Pruning
The blue Atlas cedar can be trained as it grows, and popular pruning shapes include cones, ovals, cylinders, or “weeping” shapes. In its natural growth habit, it is pyramidal in shape when young, but it develops a flat top with horizontal branches as it ages.
Though the blue Atlas cedar can be pruned slightly to keep it from encroaching on nearby sidewalks or garden plots, it is largely discouraged, as this can ruin the wild, eccentric natural shape of the tree.
Prune only to maintain or keep the shape of your blue Atlas cedar tree, and do so in early spring before new growth starts for the season. Be sure to keep at least a portion of the young growth on the tree, and never remove more than a third of the tree’s overall density.
Propagation
Blue Atlas cedar is difficult to propagate by vegetative means. Most gardeners grow new blue Atlas cedar trees by harvesting and growing seeds from the dried cones.
How to Grow from Seed
Blue Atlas cedar trees can be grown from seed by collecting ripened cones from mature trees in the fall, then freezing them just until the scales begin to open up. Once your seeds are prepared, here’s how to plant them:
- Shake the cones over a sheet of paper to collect the seeds that fall out. Soak the seeds in water overnight before planting.
- Plant the seeds 1/2 inch deep in a large, flat tray filled with a sandy seed starter mix.
- Place the tray in a sheltered outdoor location; the seeds germinate most reliably if they receive a winter stratification period of roughly one month with temperatures under 50 degrees Fahrenheit.
- Keep the potting mix moist, but not wet, until seedlings sprout. When the seedlings are large enough to handle, transplant them into individual pots filled with a blend of potting mix and sand.
- Grow the potted seedlings in a protected location for their first two winters (such as in a cold frame).
- Plant the seedling into the landscape in the spring after its second winter in the pot.2
Potting and Repotting
Blue Atlas cedar trees have a mature size that is far too large for growing in pots, so most gardeners do not plant them in containers. Young trees growing in containers can be transplanted into the ground outdoors after their second winter growing in the pot. Because these trees do not take well to being transplanted, it’s best to choose a planting location where the tree can live for its entire lifespan.
Overwintering
Within its hardiness range, blue Atlas cedar does not require any cold protection for winter, but young, sparse trees may need protection against harsh winds, which can be provided with screens or tents made from burlap and stakes.
Young trees can also be susceptible to breakage from winter snow, so it’s a good idea to shake off the snow after heavy snowfalls. Because they can be heavily browsed by deer, a tall cage or sturdy wire is a good idea to protect them from hungry deer in the winter for the first few years.
Pests and Diseases
Common Pests & Plant Diseases
Luckily, the blue Atlas cedar tree is considered to be fairly pest and disease-free, so you won’t have to do much to ensure its health and vitality. If it does come down with a pest, it’s likely that it will be scale insects or sapsuckers that damage the tree in their search for insects. Still, it’s unlikely that the pests will do serious damage to the tree, and therefore it’s rare that pest control methods or treatments are necessary.
Tip blight is an occasional fungal disease caused by several different fungi (Sirococcus conigenus, S. tsugae ,and Kabatina spp), which causes branches to die back beginning at the tips. Shake the branches to dislodge affected needles, and carefully rake up debris to remove fungal spores.
Tip blight normally runs its course in about a year, but spraying with a fungicide containing mancozeb, copper hydroxide, or azoxystrobin may help prevent infection. Fungicides are best applied as new growth is just beginning in the spring.
Common Problems
Planted in the right location and soil conditions, blue Atlas cedar is remarkably carefree. Many landscapers choose this tree for its easy-growing habits and typically low-maintenance care requirements. However, there are a few problems that you may encounter when growing blue Atlas cedar.
Sparse Growth
The most common complaint is that the trees are fairly sparse and messy-looking when they are young. This is entirely natural, so you should avoid the temptation to prune it in an effort to make it look more presentable. Left alone, it will become a much fuller, even picturesque tree within 20 years, and by 50 years of age it can be quite stunning.
Brown Branches or Needles
It’s possible that your blue Atlas cedar may experience root rot if its soil is kept too moist. If you notice the branches or needles of your tree turning brown, step back your watering cadence to allow the roots to dry out a bit between waterings.
III. Uses and Benefits
The award-winning atlas cedar might look a bit scrawny at first, but it develops into a large, full, blue-tinged evergreen that can effectively decorate any landscape all year round. It’s a solitary tree that needs a spacious area to thrive, so you can plant it as a towering centerpiece in an informal or cottage garden, particularly near ornamental buildings.
