Carter County distribution: Three populations are documented in the county. These are at 

 Medicine Rocks State Park and on BLM and Custer National Forest lands in the Ekalaka 

 Hills, including a tract of BLM and adjoining USFS-administered lands. 



HABITAT: Plains phlox occupies a wide range of habitats in the center of its range, including 

 sparsely-vegetated outcrops, sandplains, and heavy alkaline clays (Barr 1983). In Montana, it is 

 known mainly from sandy substrates that support grasslands and scattered ponderosa pine, often 

 associated with sparsely vegetated erosion microfeatures such as dunes and blowouts. It is also found 

 in open, sandy pine woodland and openings in the Ekalaka Hills. Like hairy four o'clock, this 

 species is known from both Sheridan County sandhills and on nearby glacial substrate. Unlike the 

 former, its local pattern of distribution suggested that it had been a survivor of past disturbances 

 rather than having colonized in their wake. 



The Carter County Ekalaka Hills population on BLM land is a sparsely vegetated slope with 

 scattered ponderosa pine {Pinus ponderosa) and skunkbush sumac {Rhus trilobata). This population 

 and the second Ekalaka Hills population also extend into grassland openings, and into open pine 

 woodland. 



SPECIES BIOLOGY: The plains phlox, like other prairie phlox species, often lives to a great age, 

 and has very deep, woody roots (Barr 1983). Prairie phlox species can reproduce by rhizomes as well 

 as by seeds, and are generally adapted to insect-pollination. 



The Medicine Rocks population of plains phlox was estimated to consist of over 1,000 plants, the 

 Rosebud County occurrence was estimated to consist of about 10,000 plants, and the species was 

 described as locally common at the Dawson County site. The Sheridan County occurrences were 

 documented in late June relatively late for survey and population estimate purposes, but the species 

 was recurrent in vegetation plots. In Carter Coimty, a small population on Horse Creek was 

 documented, the extent of the Ekalaka Hills occurrence was expanded significantly, and a separate 

 occurrence in open woodland was found in the Ekalaka Hills with over 100 plants. 



OTHER COMMENTS: Montana populations are in sparsely vegetated areas that receive little use 

 by livestock, and the low growing form of Phlox andicola makes it resistant to browsing. The 

 species appears to be adapted to small-scale disturbance. Given the large size of some Montana 

 populations, its distribution across at least four counties, and its close resemblance to Phlox hoodii, it 

 seems likely that Phlox andicola is more widespread than current records suggest. It is characterized 

 as "frequent on dry prairies and plains in western South Dakota" (Van Bruggen 1985). It is likely 

 that more early-season surveys will provide new records of this species, though we recommend 

 maintaining its current BLM watch status until additional occurrences are documented. The number 

 of new occurrences documented in the course of recent studies provides evidence for changing its 

 state status from SI to S2. This is one of several sand-loving species in the county that are often 

 found with other species of special concern where the habitat is extensive and/or in good condition. 



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