Agave deserti var deserti

Agave deserti, the Desert Agave, is a somewhat variable genus with three recognised varieties. Agave deserti var. deserti is found in southern California in San Diego, San Bernadino, Riverside and Imperial Counties and across the border into Baja California. The original type locality for the variety was San Felipe arroyo in San Diego County in the rainshadow east of the Palomar Mountains at an elevation of approximately 500 m. There are other slightly different leaf forms from different localities, noticeably one that originates from Pinyon Flats near the northwestern slopes of Santa Rosa Mountain. This morphological lack of distinctness is a feature across all three varieties. Gentry in his description had described three subspecies but because of this absence of consistent morphological distinctness, in 2001, Wendy Hodgson and James Reveal proposed reducing these to varietal status. Agave deserti is a true desert Agave and grows in areas that are exceptionally arid - usually in very free-draining, gravelly, granitic sand rather than a predominantly rocky scree.

Agave deserti var deserti typically produces many offsets - either from the base or from the root system - and eventually forms large clumping colonies of medium-sized rosettes with elongated glaucous-grey-green leaves that are thickly fleshed, rigid and noticably concave on the uppermost surface and deeply convex on the lower surface. The leaf structure of the rosette is arranged in a a very open habit and the way the leaves symmetrically radiate out from the centre is a wonderful example of a plant manifesting maximum efficiency in harnessing sunlight for photosynthesis. Indeed, Agave deserti var deserti is amazingly adapted to the hostile extremes of heat and aridity. It has a very shallow root system allowing it to respond quickly to any rainfall and its clonal suckering habit ensures this precious water is shared with its future offsping. It generally utilises CAM photosynthesis that enables it to take up carbon dioxide at night and to cut down on daytime transpiration loss by closing its stomata during the day yet it is also capable of switching to normal C3 photosynthesis at those times of rainfall when there is plenty of water thus enabling it to increase its growth rate. Such a clever yet modest plant !

In cultivation, I give it a very free-draining substrate approximating its natural conditions. A thick sand and gravel mix with generous quantities of added perlite to which is added a slow release fertilser and only a small amount of potting mix. Its CAM photosynthesis keeps its growth rate slow but with the above free-draining mix I find I can keep it moist for most of the summer to increase its growth. A raised desert bed with a rubble base or planted on a gravel slope are ideal for it. Stop watering it in early September and take measures to protect it from the rain. Drying it out in preparation for winter is imperative. Kept absolutely dry during the winter it is hardy to -15 C. To ensure it roots are kept dry a simple glass rain shelter can be erected. Two layers of fleece arranged in a tipi above it will also keep it dry as well as warm during the winter months. Be inventive !