CPC Plant Profile: Arizona Agave
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Plant Profile

Arizona Agave (Agave x arizonica)

The Arizona agave is a small plant, with a rosette of mahogany-edged leaves reaching only ca. 30 cm tall and 40 cm broad at maturity. Photo Credit: Lynda Pritchett-Kozak
Description
  • Global Rank: GNA
  • Legal Status: N/A
  • Family: Asparagaceae
  • State: AZ
  • Nature Serve ID: 141683
  • Date Inducted in National Collection: 03/14/1986

Agave arizonica was first discovered in 1959 in the New River Mountains of Arizona (Gentry 1970, 1982). It has been described as one of the rarest and most beautiful agaves in Arizona. The Arizona agave is a member of a prestigious family of plants, the Agavaceae. Within this family are numerous century plants that have been cultivated by humans for food, fiber, and alcohol uses. The Arizona agave is considered to be a hybrid, reportedly from a cross between Agave chrysantha and A. toumeyana v. bella. This means that A. arizonica may be just starting down the path of evolution. (Nabhan 1989, Hodgson & DeLameter 1988, DeLameter & Hodgson 1987a, 1987b). Agave arizonica is native to a small area in central Arizona, occurring on open rocky slopes in chaparral or juniper grassland at elevations from 1100 to 2750 m (3600-5800 ft). The distinctive bright green leaves of this species have mahogany margins and are generally arranged as single rosettes. This is a small plant, with a rosette of leaves reaching only ca. 30cm tall and 40cm broad at maturity. (Gentry 1982) Rosettes produce offsets sparingly in their native habitats, but when grown in cultivation plants produce clones prolifically in this manner. In May or June, a lucky observer may catch a glimpse the small, yellow jar-shaped flowers of this species that grace the top of 3-4 m long, slender stalk rising from the leaf rosette. Unfortunately, cattle grazing in areas where this species naturally occurs has severely impacted the ability of the Arizona agave to successfully produce flowers. In 1988, only 12 of 41 mature plants were able to produce flowers due to trampling and grazing from cattle in the area. (Hodgson & DeLameter 1988) Because plants are of hybrid origin, seeds produced are not necessarily representative of the typical taxon. Plants are reportedly of hybrid origin, with A. chrysantha, a relatively large agave, and A. toumeyana v. bella, a diminutive plant, as the parent species. Only 50-60 clones or plants have been located from distinct locations in Arizona where populations of the two putative parent species overlap. The Desert Botanical Garden has a long history of study associated with A. arizonica, the majority of which has been conducted by W. Hodgson, Herbarium Curator and research botanist, in association with R. Delamater. All of the in situ controlled crosses, and subsequent seed collection was completed by Hodgson and Delamater.

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    Updates
    Center for Plant Conservation
    • 11/05/2021
    • Reintroduction

    Twelve genetic individuals were selected from plants maintained at Desert botanical Garden, and three offsets were removed from each of the twelve individuals. These offsets were potted in a 1:1 mix of Supersoil : pumice with 1 tsp. of Osmocote added to each 4" pot on 9 January 1989. The plants were transferred to a lath house with40% shade. In August 1989, one set of twelve individuals was transplanted into 6" pots filled with 1:1 Supersoil : pumice. A second set of 12 genetic individuals was transplanted into 6" pots containing 50% pumice, 30% native soil and 20% coarse sand. The third group of offsets were too small to be transplanted into 6" pots. Plants were placed in full sun in September 1989 and watered every 2 to 3 weeks. In November of 1989, all of the plants were transplanted into habitat at three different sides.

    Exposure was west-southwest, and slope was about 45 degrees. The roots of the plants transplanted at Site 1 were left undisturbed, and the root ball kept intact. Planting holes were backfilled with native soil, and some rock terracing was provided down slope from plants to help augment rainfall. One liter of water was applied at the time of planting. Site 1 was fenced to prevent grazing by cattle. Sites 2 and 3 exhibited signs of rodent predation and plants were individually caged with chicken wire. The plants were stripped of the soil around the roots, and native soil was used to backfill planting holes at Sites 2 and Site 3. All plants were watered every two weeks during the first 2 months after transplanting. Watering was discontinued at the beginning of the summer rains in July.

    Survival, growth, and offset production was evaluated every 4 months. No significant differences were noted between different transplanting treatments. The bare-root planting method appeared to cause a decrease in leaf turgor. The mortality rate for Site 1 was 17%, Site 2 was 0% and Site 3 mortality was 82% by the end of the study period, July 1990. Mortality at Site 3 was attributed to herbivory, and record-breaking heat (122 F).

    All three Sites were visited during late spring, 1994. Mortality was 100%. No plants remained alive. Future attempts to reintroduce members of Agavaceae should take different site selection, and longer term follow-up care and observations into consideration.

    • 08/16/2020
    • Genetic Research

    Controlled crossed have been conducted on ex situ plants and those in habitat to ascertain whether or not A. chrysantha and A. toumeyana v. bella are indeed the true parents. Seeds resulting from these crosses produced 'typical' A. arizonica plants. Back-crosses from A. arizonica to one of the parents produced plants with characters varying in range between the two parent species, characteristic signs of introgression. The Desert Botanical Garden has successfully grown this plant both from seed and tissue culture (Powers and Backhaus 1989).

    • 08/16/2020
    • Tissue Culture

    Controlled crossed have been conducted on ex situ plants and those in habitat to ascertain whether or not A. chrysantha and A. toumeyana v. bella are indeed the true parents. Seeds resulting from these crosses produced 'typical' A. arizonica plants. Back-crosses from A. arizonica to one of the parents produced plants with characters varying in range between the two parent species, characteristic signs of introgression. The Desert Botanical Garden has successfully grown this plant both from seed and tissue culture (Powers and Backhaus 1989).

    Nature Serve Biotics
    • 05/02/2017

    Endemic to a small area in central Arizona where there are few known occurrences (sites), with a total of 50-60 clones. Threatened by collection, cattle grazing, and recreation. Extremely slow to reproduce; will not repopulate an area easily.

    Kathleen C. Rice
    • 01/01/2010

    Illegal collection is a threat to this species, especially given its slow growth rate and extremely low population numbers. (Hurd and Albee 1976, USFWS 1984). Luckily, this plant grows in locations that are relatively isolated and difficult to reach.

    Kathleen C. Rice
    • 01/01/2010

    The Arizona agave has both a limited distribution and low numbers. In 1984, when the species was listed under the Endangered Species Act, 13 populations with 1 to 7 individual plants each were known, totaling less than one hundred individual plants for the entire species. (USFWS 1984)

    Kathleen C. Rice
    • 01/01/2010
    • Reproductive Research

    Controlled crossed have been conducted on ex situ plants and those in habitat to ascertain whether or not A. chrysantha and A. toumeyana v. bella are indeed the true parents. Seeds resulting from these crosses produced 'typical' A. arizonica plants. Back-crosses from A. arizonica to one of the parents produced plants with characters varying in range between the two parent species, characteristic signs of introgression. The Desert Botanical Garden has successfully grown this plant both from seed and tissue culture (Powers and Backhaus 1989).

    Kathleen C. Rice
    • 01/01/2010
    • Reintroduction

    Tonto National Forest supported a trial augmentation conducted by the Desert Botanical Garden in the New River region (Kvale et al. 1989). Two plots containing ten plants each were watered several times, and then checked annually for establishment. After three years, only one or two plants remained. Suggested changes made to the experimental design for future attempts include alterations in site selection specifications, and in pre-conditioning of plants to be used. The road into the main habitat where Agave arizonica occurs has been closed to limit access to this endangered species. (USFWS 1984) An Allotment Management Plan (a document that applies to livestock operations on public lands or on lands within National Forests in the eleven contiguous western states--tailored to the specific range condition of the area where cattle are to be grazed, with the intent to improve the range condition of the lands involved) was signed in 1989 for the New River Allotment. This plan requires water developments for cattle to be placed greater than one-half mile from Agave arizonica, and that fences are erected one-quarter mile from known Agave arizonica locations during flowering periods. (Arizona Game and Fish Department 1997)

    Kathleen C. Rice
    • 01/01/2010

    Molecular work to determine variation within populations would be helpful in predicting the future status for this species. Plants are long-lived (ca. 15-20 years), so at this point trends and demographic changes over the long term are unknown, but need to be determined in order for proper management of the species to occur.

    Kathleen C. Rice
    • 01/01/2010

    Controlled crosses between the parent species should be conducted to produce seeds for banking at Desert Botanical Garden and the National Seed Storage Laboratory in Ft. Collins, CO.

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    Photos
    Nomenclature
    Taxon Agave x arizonica
    Authority Gentry & J.H. Weber
    Family Asparagaceae
    CPC Number 44
    ITIS 810175
    USDA AGAR8
    Common Names Arizona agave | Arizona century plant
    Associated Scientific Names Agave arizonica | Agave X arizonica
    Distribution The two populations are documented on the Tonto National Forest in central Arizona. One is located on steep granitic slopes in the New River Mountains (Maricopa and yavapai Counties). The other is l
    State Rank
    State State Rank
    Arizona SNA
    Habitat

    Endemic to a very small area on steep, rocky granite slopes, or on level hilltops, sometimes close to drainages, at about 3,000 ft elevation in upper Sonoran Desert habitat (Ecker 1990, Hodges 1990). The surrounding vegetation is a chaparral association that is a transition from an oak-juniper woodland to a mountain mahogany-oak scrub community. (USFWS 1984, Brown 1994). Associated vegetation includes Agave chrysantha, A. toumeyana v. bella, Quercus turbinella, Dasyliron wheeleri, and Arctostaphyllos pungens (USFWS 1984, Ecker and Hodgson 1991).

    Ecological Relationships

    The Arizona agave flowers in late May through June. A study conducted in 1988 (Hodgson & DeLameter) determined that bumblebees were the most frequent visitors to the inflorescences of this plant, as well as Halictidae bees, and even a wasp (Polistes sp.). Seed set appears moderate compared to A. chrysantha and A. toumeyana ssp. bella. Seed is gradually released via wind throughout the fall and winter.

    Pollinators
    Common Name Name in Text Association Type Source InteractionID
    Bees
    Sweat bees Sweat bees Confirmed Pollinator Link
    Sweat bees Halicitidae Confirmed Pollinator Link
    Bumble bees Bumblebees Confirmed Pollinator Link
    Wild bees Floral Visitor Link
    Beetles
    Beetles Floral Visitor Link
    Birds
    Hummingbirds Hummingbirds Confirmed Pollinator Link
    Hummingbirds Hummingbirds Floral Visitor Link
    Flickers Flickers Floral Visitor Link
    Doves/pigeons Doves Floral Visitor Link
    Doves/pigeons Pigeons Floral Visitor Link
    Wrens Wrens Floral Visitor Link
    Ravens Ravens Floral Visitor Link
    Flies
    Flies Floral Visitor Link
    Other
    Wasps Floral Visitor Link

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