In Howard Scott Gentry’s book, Agaves of Continental North America (published in 1982), the group Striatae, as defined by Baker in 1888, consists of three species, Agave dasylirioides, Agave striata, and Agave stricta. There have been several new species of agaves found and described since 1982, and the group Striatae has tripled in size and now contains nine members. One of the new species is Agave rzedowskiana, an intriguing little plant that hails from the southern Sierra Madre Occidental in the states of Jalisco and Sinaloa in Mexico. The species was described in 2003 by Pablo Carrillo-Reyes, Rito Vega Aviña, and Raymundo Ramírez-Delgadillo, and the original description can be found through the link here at agavaceae.com. In May 2013, Julia of agavaceae.com fame was kind enough to take me, Brian Kemble, Walker Young, and Laura and Bill Hogan to the type locality of San Cristóbal de la Barranca in northern Jalisco so we could see this handsome species. This area appeared quite barren on the flat, open ground while the majority of vegetation was concentrated on the rocky slopes and cliffs. The Agave rzedowskiana was no different and the bulk of the population seemed to be concentrated mostly on the slopes and cliffs composed of igneous rock.
Our perception of the vegetation cover is somewhat skewed since we visited near the end of the dry season so not much was happening. There were a couple of prominent trees, Quercus resinosa and Acacia pennatula, and two other agaves, Agave guadalajarana and Agave schidigera as well as several grasses and a cool looking Hechtia species. Individual rosettes of Agave rzedowskiana are compact and hemispherical and not very large, reaching about 12-18 inches in diameter with some of the clusters having 2-several rosettes and the largest clusters attaining a diameter of about 4 feet, but usually much smaller.
The shot below shows Agave rzedowskiana, Agave schidigera and the Hechtia species growing in a seemingly impossible manner tucked into the rock crevices. The way plants can grow in situations like this always fascinates me to no end.
They really favored spots that were next to impossible to get to and were teasing us with the nearly fully ripe seed pods. The plant in the center left of the shot below appears to be one perfectly symmetrical rosette, but is actually composed of at least three rosettes clustered tightly together.
Here we found a plant that was easily accessible, growing at the base of the oak tree.
The seed pods look like small cherries before they are fully ripe at which point they will become woody and turn dark brown.
As mentioned above, the group Striatae now contains nine members, and they are:
I know that there is at least one more from Oaxaca to be described and who knows how many other isolated species are lurking in the backcountry of Mexico.
In the original description, the authors compare Agave rzedowskiana to A. dasylirioides and A. petrophila. When looking at the pertinent flower measurements (ovary length, tube length and tepal length) Agave rzedowskiana seems to align more closely with A. striata and A. tenuifolia since the ovary length and tube length are twice that of the tepal length for those three species while they are all about equal in A. dasylirioides and the ovary length and tepal length are twice that of the tube for A. petrophila. I would love to work out a “species tree” for this group, but alas, other projects are calling my name at the present time. If I can generate enough interest with a geneticist, I would like to gather enough material for a thorough DNA work up for the group.