Coryphantha minima was first collected by A.R. Davis in 1931 and was described by Ralph O. Baird in American Botanist the same year. In 1934, Croizat described the species as Coryphantha nellieae, unaware of the earlier description. Backeberg transferred the species to Coryphantha nelliae in 1961, and Weniger referred to it as Mammillaria nellieae (1970). The currently accepted name is Coryphantha minima, as described by Baird in 1931. The Nellie Cory Cactus, Coryphantha minima, was listed as endangered on November 7, 1979. Primary threats include direct collection, modification of habitat through overgrazing, and natural threats.

The plants are small, round, up to 2.5 cm tall, and 1.2 cm in diameter, densely spined with yellowish spines. Flowers are rose-purple, and up to 1 cm tall, in May. Fruits are green and fleshy when ripe. Plants flowering in cultivation do not self-pollinate. Plants are restricted to desert grassland on the Caballos-Novaculite limestone formation which is located primarily on privately-owned land in west Texas. Only one known site has been accessed. Little is known about population trends in the wild. It is widely believed that there is a greater number of plants than is currently known, and additional information on the distribution and population numbers of this species may result in delisting.

The Desert Botanical Garden has been unable to visit other potential sites, and the conservation collection consists of only 7 genetic individuals, 12 field-collected seeds, and 1,910 seeds produced in cultivation. Thus, there is a critical need to locate additional populations, if they exist, and to establish conservation seedbanks from these sites for reintroduction if ever needed.

Desert Botanical Garden plans to begin germination experiments in 2000 using seeds produced in cultivation, to determine storage requirements and approximate viabilities of stored seeds. Seeds produced in cultivation may differ than those collected in the wild so the data produced from tests using such seed does not necessarily reflect the same qualities as field-collected seed. Because cultivated plants have the benefit of optimal light, watering, and environment, they produce larger seeds in larger numbers, which may be quite different from seeds produced under the relatively harsh conditions in the wild.

The 7 plants in cultivation at Desert Botanical Garden began to flower in mid-May and continued to flower through June. Based on pollination experiments performed at Desert Botanical Garden in the past, it appears that this species requires outcrossing to produce seeds. Controlled cross-pollinations were attempted in 1997, but no fruits formed. A seed germination experiment was initiated on 12 June 1997. Twenty-five seeds produced in cultivation were placed on a sterilized medium (Turface Quick-Dry) in a Petri dish in a seed germination chamber. The medium was moistened with de-ionized water. The chamber was placed on a diurnal cycle with lights on for 16 hours and off for eight. The 'daytime' temperature was set to 25°C and the 'night' temperature set to 20°C. Relative humidity was programmed at 60%, but as the air within the Petri dish containing the moistened medium was probably saturated, we can assume 100% humidity. By July 1st, thirteen days after initiation of the experiment, four seeds had germinated, with a percentage of 16%. Seedlings began to succumb to damping off, and by 9 September, 3 plants remained.

Desert Botanical Garden has 37 individuals of Coryphantha minima that were produced through tissue culture of 2 seeds. Initially, the tiny plants were undifferentiated tissue, and did not resemble Coryphantha minima. The plants have grown and individual heads can be now be distinguished. Two of these plants flowered for the first time in 1997. Cross-pollination was attempted, but no fruit resulted.

Much remains to be discovered about the Nellie Cory Cactus. Future work at Desert Botanical Garden will focus on continued efforts to better understand the horticultural requirements, reproductive biology, seed germination and viability factors and distribution of this diminutive little cactus.