Distribution, growth, and reproduction of Pima pineapple cactus (Coryphantha scheeri Kuntz var robustispina Schott)

Pima pineapple cactus (Coryphantha scheeri var. robustispina) (PPC) is listed as endangered by the US Fish and Wildlife Service. This taxon occurs south of Tucson, Arizona and Sonora, Mexico. Knowledge of this plant's distribution, growth, and reproduction is important for management. Research has documented reduced plant vigor and lack of reproduction within Lehmann lovegrass stands. PPC density and seedling presence were described at five sites in two different vegetation types. Field observations of 72 plants at five sites were monitored from fall 1993 through summer of 95 and shadehouse studies were conducted. This research resulted in five conclusions: (1) fire-induced mortality of PPC may be related to Lehmann lovegrass, (2) PPC grows vegetatively in the spring, (3) flower buds are initiated in May and open after a few summer rains, (4) seed germination follows several summer rains, and (5) cross-pollination produces significantly more PPC seeds than self-pollination