The Zocalo lies at the very heart of Mexico City, constructed by the Spanish upon the rubble of the great pyramid of the Aztecs.  This enormous open square is bounded by the national cathedral, awesome colonial facades and the Presidential Palace with its Diego Rivera murals of the history of Mexico.  If you wander in behind the Palace where few tourists tread you will find a most interesting botanical garden, planted with indigenous cacti and succulents of this region.

What stands out here are the great agaves, with giant specimens of the golden variegated Agave americana.  But there are smaller less ostentatious agaves there too, those used as agricultural crops.  Blue agave is the source of tequila and mescal.  Others are grown for their fiber which is extracted from the long fleshy leaves.  In Mexican markets you can find a wide range of products and common scrub brushes made of  agave fibers. 

What makes agave unique is the reason for its common name, century plant.  They bloom but once in their lifetime in a single massive bloom stalk.  A lifetime of energy is stored to create these massive flower-packed stalks that can reach up to twenty feet tall with some species. 

At this secret garden a rare agave was in bloom, bearing a magenta pink flowering stalk, the only one of that color I have ever seen.  Most agave flowers are green, yellow or white.  Bees hovered around the flowers to harvest the sweet nectar and pollinate this single crop.

An older stalk shows how it evolves after fertilization when the flowers have withered.  Their ovaries swell with seed, lining the stalk with pods as densely as kernels on a corn cob.  Over time the stalk will mature, weaken and fall over, spilling its contents of seed onto the soil.