The genus Agave includes numerous species with varying botanical and ecological characteristics, but all are succulents of relatively dry habitats that grow as a rosette of firm, spine-tipped leaves. The outwardly radial arrangement of leaves intercepts rainfall and conducts it toward the base and roots of the plant center. A thick waxy cuticle covering the leaves conserves moisture. Nighttime opening of leaf stomates also prevents water loss through transpiration during the hotter daylight hours. Roots are shallow and spreading to derive maximum benefit from light rains and other habitat conditions that limit moisture to upper soil layers.

Figure 1.1.2  Diagram of an agave collecting rain and irrigating itself (Gentry:Figure 2.3).

Figure 1.1.3  Typical agave growing (Gentry).

The majority of species, including all of those important in indigenous subsistence and potentially cultivated by the Hohokam, flower only once in the life of the plant. The common name “century plant” refers to the lengthy period of 8 to 25 years to reach reproductive maturity, an interval which varies according to species, the availability of water, and other conditions affecting growth. The agave stockpiles energy for a single flowering episode near the end of its life cycle, when a large central flowering stalk grows very rapidly. Carbohydrates stored in the short, thickened stem and attached leaf bases to fuel this event are the source of human food; a maximum supply is available just prior to emergence of the stalk. Tender young flowering stalks and the edible flowers and fruits of some species are gathered from wild plants. These reproductive parts are not the primary products of cultivation, however, because the flowering process depletes the more extensive supply of nutrients that farmers can obtain by prior harvesting.

Figure 1.1.4  Agave huachucensis near Sonoita in southeastern Arizona, June 1968 (citation).

Figure 1.1.5  Agave shrevei matapensis fruits and flowers (citation).

Able to withstand periodic drought, agaves offer a means to expand agricultural production onto lands too marginal for annual crops such as corn. Although optimal harvest is just before flowering, the longterm, cumulative storage of energy allows use of semi-mature plants in times of urgent need. Thus, agave crops represent the additional advantage of an emergency resource or “starvation food.” The three or more species cultivated by the Hohokam have not been conclusively identified, but Agave murpheyi is the leading candidate for their most common cultigen.

Figure 1.1.6  Agave murpheyi in bloom.