Several plant species in Arizona's Sonoran Desert are classified as endangered, most of which are succulent or cacti plants. Mining operations, off-road vehicles and over-collection are the most common reasons for plants becoming endangered in this region, as well as the plants' individual reproductive and habitat characteristics. The endangered plants in the Sonoran Desert have extremely specific habitat requirements that severely limit their viability in a wider range of areas.
Nichol's Turk's Head Cactus
Classified as endangered for more than 30 years, the Nichol's Turk's Head cactus (Echinocactus horizonthalonius var. nicholii) has a single rounded stem that's usually bluish and covered with grayish or black spines. Found growing in exposed, north-facing black limestone slopes, the Nichol's Turk's Head cactus has become endangered due to its specific habitat requirements, over-collection, extremely slow growth, copper mining and urbanization.
Kearney's Blue Star
Kearney's Blue Star (Amsonia kearneyana), also known as Kearney's Slimpod, is a perennial herb that blooms in clusters of white flowers atop 50 erect stems. This endangered plant grows in full sun or partial shade in dry washes and some vegetative areas that are surrounded by Sonoran Desert scrub. Found in only two very small populations of less than eight plants, the Kearney's Blue Star has become endangered due to flash-flooding, grazing and its isolated habitat.
A succulent plant with a flattened, globe-shaped rosette of lower leaves, the Arizona agave (Agave arizonica) has jar-shaped, pale-yellow flowers that bloom atop a stalk and can grow up to 11-1/2 feet tall. The Arizona agave grows on granite hillsides and creek bottoms in the Sonoran Desert. This agave species' population has become endangered due to over-collection, cattle grazing, deer browsing, as well as slow and poor reproduction.
Cochise Pincushion Cactus
Found in only two extremely small populations in the Sonoran Desert, the Cochise Pincusion cactus (Coryphantha robbinsorum) has a spiny, single rounded stem and grows up to only 2 inches tall. This endangered cactus blooms in pale greenish-yellow flowers during spring, followed by reddish-orange fruits in summer. Growing on grey limestone hills in semi-desert grassland areas, the Cochise Pincushion cactus has become endangered due to its very low reproduction rate, grazing, oil drilling and exploration, over-collection and off-road vehicles.
Brady's Pincushion, Peebles Navajo and Siler Pincushion Cacti
Endangered due to its limited habitat, illegal over-collection, off-road vehicles, grazing and mining, the Bray's Pincushion cactus (Pediocactus bradyi) is a small, spiny succulent with a single rounded stem that reaches only 2-1/2 inches tall and blooms a pale-yellow flower at its tip in April. Growing in just five small populations in gravelly soils, the Peebles Navajo cactus (P. peeblesianus peebles) has become endangered by gravel pit operations. This endangered cactus grows up to only 1-1/4-inch tall with rounded stems covered in white spines arranged in crosses and blooms in yellowish-green flowers in late April. Like the Brady's Pincushion, the Siler Pincushion cactus (P. sileri) has a single rounded stem, but it grows up to 5 inches tall and blooms in yellowish to maroon flowers in spring. Growing only in soils containing gypsum and soluble salts, this species has become endangered from gypsum strip-mining.
Arizona Hedgehog Cactus
Becoming endangered from over-collection and open-pit copper mining, the Arizona hedgehog cactus (Echinocereus triglochidiatus var. arizonicus) is a spiny succulent with several cylindrical stems and deep-red flowers and fruits. The Arizona hedgehog cactus grows in oak woodlands or in clumps near granite boulders in the Sonoran Desert.