Agave shawii

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.

Agave shawii

11 responses to “Agave shawii”

  1. Connie

    Plants are such a joy with so much diversity! Thank you for your educational service.

  2. kathryn corbett

    Yay, Asparagaceae! How fine to see the close resemblance of this Agave’s huge inflorescence to a stalk of asparagus about to bloom. Actually, aren’t many (all?) of the Agaves semelparous?

  3. Jonathan

    This may seem picky, but I’ve heard about the “flower and die” habit of century plants, and that they often regrow from vegetative pups, I’ve always wondered: why then is this considered dying? What technically defines something as semelparous (I had known “monocarpous” before, thanks for the new word) if in fact the plant does survive? Sure, the rosette dies, but if its root system typically lives on and supports a clone of itself, how is the plant meaningfully dying versus, say, the way a daffodil “dies back” each year to its bulb, and often produces bulb offshoots, but certainly does not “die”? Any idea? The wikipedia page you linked didn’t seem to answer this for me.
    Thank you, Bryant! I recently taught a Plant ID class, and this site made the top seven URLs I gave my students as a “fun to follow” list at the end. I’ve been reading almost daily for a few years.

  4. Kat Berryere

    I really enjoy the diversity of the pics, but I would like to have some plants that are slightly challenging for the area that I am in, in Red Deer AB, with something of a microclimate. The pictures you show often arent that useful for my purpose.

  5. Mary Yee

    Beautiful subject, beautiful photo, thanks. Very interesting to read of its reproductive strategies.

  6. Bryant DeRoy

    I would agree that there is some cloudiness around what truly defines the agave as a semelparous organism. In this case, semelparity in the agave refers to the original individual basal rosette or ramet that produced the reproductive stem. However, you could consider the genet (colony of clones) to be iteroparous in agaves (as mentioned by Arizaga et al. 1995).
    Clones or pups of the agave are physically new individuals each with the capacity to reproduce– like offspring; however, the clones can all be genetically identical (although there is a chance of mutation) and may share root tissue with the original parent individual, which can allow them to be grouped as an individual colony or genet. It seems the cloudiness around defining Agaves as semelparous comes from the confusion of ramet vs. genet scale.
    Thanks for bringing this up! Does this clarify at all?
    This abstract/ paper may be of interest as well:
    Ricardo Scrosati. 2002. An updated definition of genet applicable to clonal seaweeds, bryophytes and vascular plants. Basic and Applied Ecology 3(2): 97-99.
    Kathryn: Most agaves are considered semelparous, but there are a few species that are considered iteroparous (e.g Agave striatus), See:

  7. Stephen Lamphear


  8. Eleanor Ryan

    I am very happy to learn about the Tilden Botanical Garden in Berkeley. Will plan a stop there on next California trip.

  9. Daniel Mosquin

    Eleanor, I was there today. Definitely worth the trip, if you are botanically-inclined or like to photograph. Many rare Californian plants. If you need any interpretation though, try to catch one of the docent tours, as there is no interpretative signage.

  10. Ruth

    Who would have guessed that Asparagus would dominate Agave in a nomenclature battle for the Family title 😉

  11. Eric Simpson

    Tilden was one of my favorite haunts during the brief time I lived in the Bay area, and the Gardens are fantastic. I don’t know if they still do it, but at the entrance to the gardens were pigeon-holes containing packets of CA native seeds that were free for the taking.

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