The remaining population within California that was confirmed as naturally occurring was located near Border Field State Park, until destroyed by the Federal Government using the Department of Homeland Security's national security policy. It allowed the habitat destruction to build the fence and adjacent cleared open area designed to attempt preventing immigrants illegally entering the U.S. 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 speculation as to whether this is a relict population or was 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 in Baja California, Mexico. The geographic separation of the two California population sites is approximately 15 miles.
Agave shawii 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.
Varieties and subspecies
- Agave shawii var. shawii 
- Agave shawii subsp. goldmaniana (Trel.) Gentry — 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.
This agave species 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.
- California coastal sage and chaparral ecoregion
- California chaparral and woodlands
- Flora of the California chaparral and woodlands
- 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" (PDF). Fremontia 36 (4): 3–10.
- CalFlora: Agave shawii var. shawii
- 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
- Calflora Database: Agave shawii (Shaw's agave, coastal agave)
- Jepson eFlora treatment of Agave shawii
- USDA Plants Profile for Agave shawii (coastal agave)
- Agave shawii — UC Photos gallery
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