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Plant Highlight: Agave isthmensis
Updated December 2023:
Our July 2004 plant highlight featured an Agave which we originally received as Agave verschaffeltii. Since this name is listed a synonym of Agave potatorum, our highlight gave this latter name for it. A. potatorum is normally a single-headed species, while our plant produced a modest number of offshoots to form a small clump. The rosettes of leaves were also smaller on our plant than is usual for A. potatorum, and its inflorescence was smaller. We therefore referred to it as an atypical, offsetting form of the species. A visiting botanist from Oaxaca, upon seeing the plant, informed us that it is actually a different and more recently-described species, Agave isthmensis. Thus, we are changing the highlight to reflect this.
Taxonomy
Agave isthmensis is included in the group Hiemiflorae, whose members are found in southeastern Mexico and Central America. As a general rule, plants in this group have relatively short lateral branches on the inflorescence, and tight ball-like clusters of flowers. They typically are winter-flowering, although our plant at the Ruth Bancroft Garden is a little earlier, with a September to December flowering period.
About the plant
The name “isthmensis” is a reference to the Isthmus of Tehuantepec, the narrow part of Mexico in eastern Oaxaca and southeastern Veracruz, with the Pacific Ocean to the south and the Gulf of Mexico to the north. This is where the plant is found in nature, both near the Pacific coast and farther inland. Agave isthmensis is closely related to Agave potatorum, a widespread species farther to the west, occurring both in Oaxaca and in neighboring Puebla, but A. potatorum is a larger plant that is generally single-headed, while A. isthmensis typically forms a cluster of several small heads. While the size of a mature head is variable, it is usually not more than 14 inches (36 cm).
About the leaves
The thick glaucous bluish or blue-green leaves of Agave isthmensis are more or less paddle-shaped, but with crenellated margins armed with small but sharp teeth. The teeth are initially reddish-brown, but they darken as they age. At its apex, the leaf tapers to a sharp pont, the tip being colored like the marginal teeth.
About the flowers and fruits
As is usual with agaves, A. isthmensis has monocarpic rosettes, so that at maturity the growing tip elongates into a tall flower stalk and no further leaves are produced. The stalk attains a height of up to about 7 feet (2.2 m), with numerous short branches in its upper half, each ending in a small cluster of light yellow flowers. Pollinated flowers produce oval brown capsules with pointed tips, these being uo to a little less than an inch long (2.2 cm). Within are three chambers holding stacks of shiny black seeds. At maturity, the capsules dry and split open to release the seeds.
Care and maintenance
Though it has limited cold tolerance, Agave isthmensis is relatively easy to grow, either in a pot or in the ground. It likes plenty of sun, as well as occasional water during its growing season in the summer and fall months. Plants grown in too much shade will lose the compact form that is part of the plant’s charm. Good drainage is important, as is the case with most succulent plants.
