Agave
Credits
Article from Bean's Trees and Shrubs Hardy in the British Isles
Recommended citation
'Agave' from the website Trees and Shrubs Online (treesandshrubsonline.
Family
- Asparagaceae
Editorial Note
The systematics of Agave has been the subject of controversy over recent years, since the genus was first identified as polyphyletic in the mid 1990s, Bogler & Simpson (1996) having shown that the morphologically distinct genera Manfreda, Prochnyanthes and Polianthes were nested within the Agave clade. The customary opposing approaches to restoring monophyly – lumping versus splitting – have been taken by different taxonomists in the years since. Thiede (2000) transferred the three nested genera into Agave to obtain a large monophyletic clade, though the wide range of morphological variation introduced by the incorporated genera lessened the information-value of the revised taxonomy. By contrast, Vázquez-García et al. (2024) achieved a more granular result by splitting off three new segregates from Agave – Echinoagave, Paleoagave and Paraagave – which enabled the three original nested genera to be upheld within a monophyletic system.
Bean treated only two species of Agave, but many more have been proven hardy in our area of study since his account was written. We reproduce below Bean’s text, adapted to reflect the updated taxonomy, pending a full, revised account, to be provided when funding allows. If you would like to sponsor the account of this genus please write to editor@treesandshrubsonline.org
Depending on which circumscription is adopted, the genus contains between 200 and 265 species (Thiede, Smith & Eggli 2019) ranging from the south-western part of the United States to S. America, but with its centre in Mexico, where more than one hundred species have been described. The leaves form a rosette springing from a root-stock or short trunk, and are commonly thick and leathery; in many species they are armed with formidable teeth and terminate with a horny spine; in length they vary from a mere 6 in. to the 7 ft or more attained in species like A. atrovirens. After a period of years – never so long as the one hundred suggested by the popular name “Century Plant” – an inflorescence grows out from the heart of the rosette and, nourished by water and nutrients stored in the leaves, develops with remarkable rapidity. In the larger species it attains, in the course of a few weeks, the dimensions of a good-sized tree, heights of 30 ft being not uncommon. The rosette that bears the inflorescence invariably dies after flowering, but in many species off-sets continue the life of the plant. The inflorescence is most commonly branched, but in a minority of species it is a simple spike.
Several species, notably Agave fourcroydes and A. sisalana, are grown in the warmer parts of the world for their valuable fibre. The Mexican national drink pulque is fermented from the sap of several species, A. atrovirens being the most prized. The agaves played a vital role in the pre-hispanic civilisations of Central America, providing both paper and fibre as well as pulque.
Two species are or have been grown outdoors in the British Isles and proved fairly hardy.