Bryant again authored today’s entry. He writes:
Thank you to Sandy Steinman (Sandy Steinman@Flickr or his blog, Natural History Wanderings) for today’s image of Agave shawii (commonly referred to as Shaw’s agave). The photo was contributed via the Botany Photo of the Day Flickr Pool.
Agave shawii is a small- to medium-sized member of the Asparagaceae. Basal rosettes of the plants, comprised of thick fleshy leaves with robust marginal spines, usually reach heights of about a meter (3 ft.) high and just under a meter wide upon maturity. It is native to Baja California as well as a few localities in southern California; this particular specimen was photographed at the Regional Parks Botanical Garden in Tilden Park, Berkeley, California.
The reproductive stalk pictured above grows about 3-5 meters (10-16 feet) tall and typically only flowers once! Like most species of Agave, Agave shawii is semelparous, meaning the rosette typically dies after it flowers. Many agaves allocate upwards of 50% of the measureable energy stored within their biomass to forming the reproductive structure and nectar for the proliferation of flowers; Agave shawii can take up to 30 years or more to do so depending on environmental conditions. Though the reproductive process may kill the parent individual, many agaves take up insurance measures in the form of vegetative rosettes that often form on the roots or sometimes the reproductive stem before, during or after the reproductive cycle takes place (see: Arizaga et al. 1995. Insurance against reproductive failure in a semelparous plant: bulbil formation in Agave macroacantha flowering stalks. (PDF) Oecologia. 101:329-334.). Therefore, clones of the parent individual may survive for centuries–often in small colonies.
It should also be mentioned that this species is considered rare and endangered in its California distribution, and imperiled/vulnerable globally.