Morphology and architecture of Cedrus atlantica Manetti

Growth in Cedar is rhythmic and all axes are built up by a succession of annual shoots. The shoot growth rate decreases progressively from the main stem, which grows in a vertical direction, to the branches and the branchlets, which grow in a horizontal direction.


Young tree and architectural unit Architectural unit

At the young development stage, the tree presents a pyramidal form. This architecture shows a very precise organisation as regards the nature and relative position of morphological discernible categories of axes. In young individuals of Cedrus atlantica, five different categories of axes may be identifiable.

The main stem is a vertical monopodial axis with indefinite and rhythmic growth. Its branching pattern is rhythmic.

The branches may have differed (proleptic) or immediate (sylleptic) development according to their position on the annual shoots. The branches are arranged in pseudowhorls. They have a horizontal to slanted direction of growth. Branches have long term definite and rhythmic growth and follow a monopodial and rhythmic branching pattern.

Branchlets are regularly arranged on branches more or less in a single plane. They have long term determinate growth. Their direction of growth is horizontal. Like branches, branching pattern of branchlets is differed or immediate development.

Twigs have rhythmic branching with differed development.

Twigs have medium term determinate growth.

Brachyblasts have short-term determinate growth, remain unbranched. They bear terminal male or female cones.

Adult tree

After the expression of its architectural unit, the tree will continue to develop its trunk and to remain regularly branched. The oldest branches increase their volume by a process of partial reiteration of the architectural unit. At the top of the branches, a sub-apical bud of the annual shoot develops into a vigorous shoot. This phenomenon gives rise to a fork formation. Thus, the repeating of this process leads to the development of branches. In subsequent years, this phenomenon of fork formation gradually invades the branches.

Sexuality appears at this development stage of the tree. The female or male flowers are terminal on brachyblasts which are formed by 3 or 4 vegetative short shoots.

Female flowering affect brachyblasts borne by the most vigorous axes: the main stem, the branches and reiterated branchlets. Male flowering is located on brachyblasts corresponding to the highest orders of branching.


Cedrus atlantica. (Photos S. Sabatier, CIRAD)
     Top left to right, and bottom: From young tree to mature tree
     Bottom right female (top) and male cones (bottom)


As the tree continues its development, new branches located in the upper part of trees develop in accordance with the architectural unit of these species. In the lower part of trees, the branches form more and more shorter annual shoots and finally die.

The architecture of the old tree tends to bend and only some branched systems still grow upwards.

Old tree

As the tree becomes older, the growth of the main stem gradually decreases. The direction of growth becomes oblique to horizontal. The main stem gradually follows the development pattern of a branch. This phenomenon involves the edification of a "tabular form" of crown.



Diagram of a Cedrus atlantica architectural unit (S. Sabatier, CIRAD)
     a) tree elevation view
     b) view of a tier of branches
     c) view of a twig annual shoot bearing several short shoots


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