It is a small-to-medium agave, with green ovate leaves 20–50 cm long and 8–20 cm wide, and a variable pattern of marginal teeth. The inflorescence forms a panicle 2–4 meters in height, whose 8–14 lateral umbels are subtended by large purple bracts. Each umbel consists of a mass of yellowish or reddish flowers.
It generally flowers February to May, and as typical for agaves, the rosette dies thereafter. Although capable of reproducing by suckering, populations vary considerably in their behavior, with some consisting entirely of individual rosettes, while others form groups or colonies of clones.
Subspecies goldmaniana is generally larger, with longer (40–70 cm) lanceolate leaves, and 18–25 umbels on a 3–5 meter stem, and predominates in the desert of the central peninsula.
Although occasionally cultivated, this agave is frost tender, with damage starting at −5°C and becoming extensive at −8°C. Plants in containers have been able to survive 18°F with no damage located on the Central Coast. Frost cloth has also allowed plants to survive well with temperatures well below freezing for long periods (days) without damage. Plants enjoy a sandy loam soil that has good drainage. Roots are very rapid responders to rain and dry plants have been documented to start growing feeder (rain) roots within 3 hours after exposure to the rain. Plants are subjected to mealybug attack and systemic treatments should be used regularly. Plants develop best color when exposed to full sun along the coast. Some relief from the hot afternoon sun in the inland valleys would provide the best results for growers. A slow growing plant, the young may take 5 years to reach a good 2 gallon container size. Plants bloom from 30 years old on, with prolific pupping prior to dying post flowering. Seeds are best sown fresh with no stratification required. A great landscape plant that should enjoy more popularity when larger numbers make the plant more readily available. Very few nurseries are growing this plant.[original research?]
The remaining population within California that is confirmed as naturally occurring located near Border Field State Park was destroyed by the Federal Government using the Department of Homeland Security's national security policy that allowed the destruction in order to construct the triple fence designed to prevent immigrants coming over the border from Mexico. Local native plant ethusiasts and nurserymen acted quickly to remove and rescue as many of the plants that could be saved within a very limited timeframe. Plans are to reestablish the population post development with the wild collected plants. There is another listed population located at Cabrillo National Monument. There is much speculation as to whether this is a relict population or what planted there are some time in the past. Genetic studies have not been conducted to determine if the population is related to either the Border Field population or those farther south. The geographic separation of the two populations is approximately 15 miles.
- Agave shawii var. shawii
- Agave shawii subsp. goldmaniana (Trel.) Gentry
- The Plant List, Agave shawii
- Engelmann, Georg. Transactions of the Academy of Science St. Louis 3:314, t. 2-4. 1875.
- Clark, K.B.; Dodero, M.; Chavez, A.; Snapp-Cook, J. (2008). "The threatened biological riches of Baja California's Colonet Mesa". Fremontia 36 (4): 3–10.
- Raymond M. Turner, Janice E. Bowers, and Tony L. Burgess, Sonoran Desert Plants: an Ecological Atlas (Tucson: The University of Arizona Press, 1995) pp. 63-65
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