Opuntia phaeacantha Engelmann. Tulip Prickly-pear. Phen: May-Jun; Aug-Oct. Hab: Limestone glades, westwards more general in rocky, sandy, or gravelly soils of open or lightly wooded areas. Dist: KS to CA south to TX and Mexico; disjunct in c. TN.

Origin/Endemic status: Native

Taxonomy Comments: Specimens from c. TN do not fit within the circumscription of O. cespitosa, the common species for that region, and are here tentatively treated as O. phaeacantha, but need additional study. These populations differ from O. cespitosa by their growth form, forming ascending shrubs, with chains of cladodes produced mostly parallel to the ground surface, and the cladodes that maintain turgidity throughout the year, instead of becoming cross-wrinkled during the winter, as in O. cespitosa. An additional assumption that these TN populations were merely an escape from cultivation (see Majure 2012c, under O. phaeacantha) has been altered by the discovery of additional populations of this taxon in central TN. At least one of the three populations is confined to cattle grazing areas and could have been introduced via cattle imported from the western US. However, more work will be necessary to determine where this taxon originated, as these populations are far out of the range of this western species. The material from central TN is smaller and not as spiny as typical O. phaeacantha, but at least one population from Wilson Co. has been recorded as hexaploid (2n=66; Majure et al. 2012a), the same ploidal level as that of other O. phaeacantha populations. The other populations are currently being studied to more appropriately treat this taxon and determine its origin in the se. US. Opuntia phaeacantha s.l. is a species complex comprised of numerous morphotypes, which needs careful morphological, cytogenetic, and molecular-based study.

Synonymy: = FNA4, K3, K4, Mex; > Opuntia orbiculata Salm-Dyck ex Pfeiff.; > Opuntia phaeacantha Engelm. var. camanchica (Engelm. & J.M.Bigelow) L.D.Benson – GrPl, NcTx, Weniger (1984); > Opuntia phaeacantha Engelm. var. major Engelm. – GrPl, NcTx, Tx, Weniger (1984); > Opuntia phaeacantha Engelm. var. phaeacantha – GrPl, Tx

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Heliophily: 9