|The Botanic Garden
of Smith College
Cupressus dupreziana, commonly called Saharan cypress, is a conifer belonging to the Cupressaceae. Cupressus dupreziana is one of 13 species in the genus. Closely related to Chamaecyparis, Cupressus plants are fast-growing trees found in hot, arid regions in both the Old and New World. They are believed to have spread both from western North Africa to China and from western North America to Guatemala.
The Saharan cypress is native to a small, dry, mountainous region of the Sahara in southeast Algeria. Very few trees remain alive in their natural environment. The conservatory collections of the Botanic Garden of Smith College include two trees that were grown from seed collected in 1985 on the Tassili Plateau, an area famous not only for the Saharan cypress but for thousands of prehistoric cave paintings.
We have sought to propagate our two C. dupreziana to enable distribution to other botanical gardens for study and preservation purposes. Conservatory Manager Rob Nicholson and Smith student Bibiana Garcia Bailo '00 conducted the propagation trials. Cuttings taken from the two plants (designated clones A and B) were treated with various concentrations of indolebutyric acid (IBA), a synthetic auxin substitute (auxin is a phytohormone that promotes root formation), stuck in a sand/perlite medium, and placed either on an open bench with no bottom heat (50-60°F) or on a mist bench with bottom heat (60-75°F).
The data obtained from this experiment provided valuable insight on the most effective propagation methods for Cupressus dupreziana. The stem cuttings did poorly under the first set of conditions. None of 100 cuttings rooted at 50-60°F, despite the IBA treatment. Cuttings did root successfully, however, with intermittent mist and bottom heat. Clone A cuttings soaked for 24 hours in 500 and 1000 parts per million (ppm) IBA were the most successful, with 9 of 10 cuttings rooted at each concentration. For clone B the 500 ppm IBA treatment was also the most successful (7 of 10 cuttings rooted), but, unlike in clone A, the 1000 ppm IBA soak was not very successful (3 of 10 rooted). Despite this, the 500 and 1000 ppm IBA 24-hour soaks were overall the most successful. They had a combined clone A and B percentage rooting of 70%, versus 45% for combined 10,000 and 20,000 ppm IBA 10-second dips, and 50% for combined control cuttings with no IBA.
These results allow us to make the following observations:
Cupressus dupreziana cuttings rooted successfully under intermittent mist with an ambient temperature of 60 to 75°F, when they were provided bottom heat. However, they did not root in a drier, cooler environment in which they were not provided with bottom heat.
An indolebutyric acid treatment consisting of a slow, 24-hour soak of the cutting at a low concentration (500 to 1000 ppm IBA) produced better rooting than a treatment consisting of a fast, 10-second dip of the cutting at a high concentration (10,000 to 20,000 ppm IBA), and was more successful than a control treatment where no IBA was provided.
We are now able to suggest more reliable conditions for vegetative propagation of Cupressus dupreziana and to contribute to propagating this endangered conifer, distributing the taxon worldwide, and making the spread and cultivation of new specimens more successful and easier.
For further reading, see Keith D. Rushforth, Conifers,
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