''Eurybia saxicastelli'', commonly known as the Rockcastle aster, is an

herbaceous Herbaceous plants are vascular plants that have no persistent woody stems above ground. This broad category of plants includes many perennials, and nearly all annuals and biennials. Definitions of "herb" and "herbaceous" The fourth edition of t ...

perennial A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is often used to differentiate a plant from shorter-lived annuals and biennials. The term is also wide ...

native to the south eastern

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

. It is present only in the states of

Kentucky Kentucky ( , ), officially the Commonwealth of Kentucky, is a state in the Southeastern region of the United States and one of the states of the Upper South. It borders Illinois, Indiana, and Ohio to the north; West Virginia and Virginia to ...

and

Tennessee Tennessee ( , ), officially the State of Tennessee, is a landlocked state in the Southeastern region of the United States. Tennessee is the 36th-largest by area and the 15th-most populous of the 50 states. It is bordered by Kentucky to th ...

along the

Rockcastle River The Rockcastle River is a U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map accessed June 8, 2011 river primarily in Rockcastle County, Kentucky, United States. It is a tributary of the Cumberland Ri ...

and the nearby Big South Fork River. As a result of its extremely restricted range as well as human alterations to its habitat, it is considered critically imperiled by

NatureServe NatureServe, Inc. is a non-profit organization based in Arlington County, Virginia, US, that provides proprietary wildlife conservation-related data, tools, and services to private and government clients, partner organizations, and the public. Nat ...

. The flowers appear in the late summer through fall and have

ray floret The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae w ...

s that are pale blue to pale white and yellow

disc floret The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae w ...

s that turn purplish with age.

Distribution and habitat

''Eurybia saxicastelli'' is present in the southeastern United States, where it is restricted to the states of

and

. More specifically, it is only known from a 5 kilometer stretch of the banks of the Rockcastle River and about 14 occurrences along the Big South Fork River, which is nearby. It is found primarily growing at the back edge of

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...

river bars composed of boulders and cobbles, along with other shrubby vegetation. These areas are flooded in the spring, but dry in the summer, making the habitat quite specific. Of the areas where it can be found, it is typically between 1000 and 1500 meters elevation, but in some cases it is found at sites as low as 600 meters.

References

saxicastelli Endemic flora of the United States Flora of Kentucky Critically endangered flora of the United States {{Astereae-stub