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Apocynaceae
Amsonia kearneyana, or Kearney's Blue Star is a perennial herb in the dogbane family (Apocynaceae), with many erect, hairy stems and alternate, lance-shaped leaves. The root crown of the plant initiates stem and leaf buds by mid-February, and plants stop growing by September to October. By December, they are completely dormant. Pale blue flowers are produced in terminal clusters in April. Fruits are papery follicles with corky, cylindrical seeds.
Kearney's Blue Star is known from only a single extant population in Pima County, Arizona. In 1986, a brief check of the population reported only eight plants. Another natural population of Kearney's Blue Star was documented by a herbarium specimen collected by Goodding on May 14, 1941, but a 1992 search proved to be unsuccessful.
Plants occur at 3,700 ft. elevation, and inhabit a dry, rocky washes. Associated plant communities are Sonoran Desertscrub and Semidesert Grassland, with the dominant species including Quercus oblongifolia, Acacia greggii, Celtis pallida, Gossypium thurberi, Ptlea angustifolia, Juglans major, and Prosopis velutina.
Amsonia kearneyana was listed endangered in 1989 because of its limited distribution, apparently declining population numbers, declining habitat due to overgrazing, and poor reproduction. Overgrazing contributes to loss of shade plants, trampling, and changes in soil characteristics. Like other members of the dogbane family, Kearney's Blue Star has a toxic milky alkaloid sap and is not grazed, even during periods of drought when other food sources are limited. Plants are also susceptible to damage from catastrophic floods, and since the natural population occurs among boulders and coarse alluvium along one drainage, a single flood could remove the entire population.
Potential sites for reintroduction were surveyed and Kearney's Blue Star was planted in the fall of 1988. Approximately 200 plants were transplanted during the fall of 1988 and spring of 1989. Plants were hand watered every one to two weeks during summer of 1989. After a spring flood scoured out the drainage where the natural population is located, as well the reintroduced site, only 33 plants remained in both sites. The 33 plants found in 1991 were supplemented with 69 additional plants in 1992.
Desert Botanical Garden has a strong mission to conserve rare flora of the U.S. southwest. A seedbank of wild-collected seeds has been established at Desert Botanical Garden as an 'insurance policy' against extinction. Germination tests are periodically conducted on these seeds to determine percent viability and optimal germination conditions. In additon, seeds produced on plants grown from wild-collected seed are produced and stored for research purposes. Plans are in effect to expand display areas to accomodate increased conservation-oriented plantings.
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