Amsonia tharpii (Tharp's blue-star)
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Perennial suffrutescent herb; stems from a woody rootstock, up to 2 dm tall; leaves subsessile, crowded, up to 5 cm long and 12 mm wide, those on the lower half of the stem elliptic-lanceolate and those above linear to linear-lanceolate; flowers pale-blue or greenish-white, salverform, the tube about 15 mm long and constricted at orifice; fruit two short, thick follicles, glabrous, 25-35 mm long. Flowers April to May.
Tharp's blue-star is the only Amsonia in this region with dimorphic leaves. Amsonia longiflora is sympatric but distinguished by its narrow lower stem leaves and longer (25-45 mm) fragrant flowers.
New Mexico, Eddy County; Texas, Pecos County.
Limestone and gypsum hills in Chihuahuan desert scrub communities; 900-1,150 m (3,100-3,500 ft).
Only four populations of this plant are presently known in New Mexico.
There is active gas development in the vicinity of two of the New Mexico populations. Extensive surveys in 2012 & 2013 documented only 2 additional sites.
Correll, D.S., M.C. Johnston and collaborators. 1979. Manual of the vascular plants of Texas (2nd printing). Texas Research Foundation, Renner (2nd printing by University of Texas at Dallas, Richardson).
McLaughlin, S.P. 1982. A revision of the southwestern species of Amsonia (Apocynaceae). Annals of the Missouri Botanical Garden 69:336-350.
Roth, D. 2013. Status report Amsonia tharpii (Tharp's bluestar) on NM State Trust Lands (Section 6, Segment 27). Unpublished report prepared by the Energy, Minerals, and Natural Resources Department, Forestry Division, for the U.S. Fish & Wildlife Service, Region 2, Albuquerque, NM.
Roth, D. and R. Sivinski. 2019. Status survey and report. Tharp's bluestar (Amsonia tharpii). Unpublished report prepared by the Energy, Minerals, and Natural Resources Department, Forestry Division, for the U.S. Fish & Wildlife Service, Region 2, Albuquerque, NM.
Natural Heritage New Mexico. 2014. Status survey for Tharp's bluestar in the Carlsbad, New Mexico area. Final Report. Natural Heritage New Mexico report 14-GTR-384.