Centaurea stoebe ssp. micranthos Centaurea stoebe L. ssp. micranthos (Gugler) Hayek Acosta maculosa auct. non (Lam.) Holub Centaurea biebersteinii DC. Centaurea maculosa auct. non Lam. Spotted Knapweed
Spotted knapweed, a native to eastern Europe, was introduced to North America in the early 1900s, as a contaminant in seeds for crops. It has since spread prolifically through much of the U.S. and Canada, where it competes with forage plants intended for livestock. It is considered an invasive species in many areas. Forage animals will eat it only as a last resort. Identification: These ungainly plants average about 24" (60 cm) in height and reach up to 4' (1.2 m). The leaves at the base of the plant are somewhat pale, with oval-shaped leaflets growing alternately from the main portion of the leaf. Thin stems with many branches form a tangle in the upper part of the plant, with very narrow leaflets less than 1" (2.5 cm) in length. The flowers are a pink to purple (rarely white) in color, about ¾" (1.9 cm) in diameter, with each petal branching several times. Spotted knapweed flowers bear a superficial resemblance to those of ragged robin: both disheveled-looking, both similar in hue. If you look closely, though, knapweeds are composite flowers (like other members of the large aster family)—they are composed of ray flowers and disc flowers. Ragged robin flowers have petals, but no central disc. Composite flowers, such as daisies, are typically composed of a central disc containing many small tubular disc flowers, surrounded by flat ray flowers. The ray flowers are often called petals, but each “petal” is actually a complete flower. Some composite flowers have only disc or ray flowers. “Composite” designates an aggregation of many small flowers that resembles a single flower, rather than two different types of flowers. The involucral bract is sometimes an important identifying feature—for example, this is where the spots are in spotted knapweed. Finally, the receptacle is where the parts of a flower head come together. Spotted knapweed and ragged robin are compared below. See also Centaurea. Online References:
Centaurea stoebe ssp. micranthos on the USDA Forest Service's Fire Effects Information Database Centaurea stoebe ssp. micranthos on the Plant Conservation Alliance’s Alien Plant Working Group Least Wanted List Centaurea stoebe ssp. micranthos on Forestry Images Centaurea stoebe ssp. micranthos at the USDA National Invasive Species Information Center Centaurea stoebe ssp. micranthos on Invasive.org, Center for Invasive Species and Ecosystem Health (PDF) Centaurea stoebe ssp. micranthos on SEINet—the Southwest Environmental Information Network References:
Old, Richard, 1200 Weeds of North America DVD, XID Services, Inc., 2012 7/31/2018 · Andres Art Institute, Big Bear Mountain, Brookline, NH 7/31/2018 · Andres Art Institute, Big Bear Mountain, Brookline, NH 7/31/2012 · Bemis Rd Conservation Area, Pepperell, MA 7/19/2017 · WV 8/4/2009 · Near Nashoba Hospital, Ayer, MA Centaurea stoebe ssp. micranthos description by Thomas H. Kent, last updated 25 Dec 2018. © FloraFinder.org. All rights reserved. |
7/19/2017 · WV 7/19/2017 · WV That's a clearwing moth, possibly Hemaris thysbe, not a hummingbird! · 7/28/2013 · Andres Institute of Art, Brookline, NH 8/4/2009 · Near Nashoba Hospital, Ayer, MA 7/28/2013 · Andres Institute of Art, Brookline, NH 7/31/2018 · Andres Art Institute, Big Bear Mountain, Brookline, NH 7/21/2010 · Nashua River Rail Trail, Ayer, MA 7/28/2013 · Andres Institute of Art, Brookline, NH 7/30/2012 · Tom and Susan’s, Pepperell, MA 9/6/2018 · Tom and Susan’s, Pepperell, MA 7/31/2012 · Bemis Rd Conservation Area, Pepperell, MA 8/6/2009 · Nashua River Rail Trail, Groton, MA 7/31/2012 · Bemis Rd Conservation Area, Pepperell, MA Range:
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