This perennial herb from the Sunflower family (Asteraceae) is distinguished by tightly clustered flower heads on the shoot ends. They are usually in colonies of 50-200+ shoots that spread vegetatively by rhizomes (an underground, horizontal stem). The shoots that are not flowering are usually less than half the length of the flowering shoots. The leaves can be as long as one inch, are alternate and are placed evenly along the stem. (Pojar &MacKinnon, NHP field Guide, Hitchcock). White top aster habitat is open grassland and is dominated by Idaho fescue (Festuca idahoensis). Fire is thought to have played a major historical role in the maintenance of the grassland habitats occupied by A. curtus. (NHP Field Guide). Major threats to the species are loss of habitat by Scots broom (Cytisus scoparius), an invasive plant, and by encroaching Douglas fir (Pseudotsuga menziesii) because of the loss of fire. (Hitchcock, et al 1973 ; Giblin 1997; NatureServe 2003; Selected Rare Vascular Plants of Washington 2000; USDA, NRCS. 2002)
|Common Names||Columbia white top aster | Curtus' aster | white-top aster|
|Associated Scientific Names||Sericocarpus rigidus | Aster curtus|
|Distribution||Aster curtus is restricted in distribution to only a few regions within the west coast of North America: the Willamette Valley-Puget Lowlands in Oregon and Washington and the southeastern portions of|
Open grasslands dominated by Idaho fescue (Festuca idahoensis) are home to the white-topped aster. And these grasslands are surrounded by Douglas fir trees (Pseudotsuga menziesii). The grasslands are typically moist most of the year, but dry, or moisture-stressed, during late summer. Southern populations occur in clayey soil, central populations in glacial outwash soil and northern populations in exposed bedrock. Other native species found in the grassland home of white-topped aster are snowberry (Symphoricarpos albus), service berry (Almelanchier alnifolia), Oregon sunshine (Eriophyllum lanatum) and early blue violet (Viola adunca). A non-native species found within white-topped asters habitat is Scots broom (Cytisus scoparius). This species poses a threat to Aster curtus by growing in dense stands and altering the soil nutrients. (Rare Care)
A. curtus is thought to have a relationship with fire where fire maintains its grassland habitat; frequent fires that burn at low intensity and soils that are seasonally dry keep the grasslands free from encroaching trees (Giblin 1997).
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