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White Tackstem

Calycoseris wrightii

Tackstem, Calycoseris wrightii, photo © by Michael Plagens

Observed in Telegraph Pass at South Mountain, Phoenix, Maricopa Co., Arizona. April 2010.

FLOWERS: All of the florets in the head are strap shaped with those around the perimeter enlarged as rays; the ends of most straps have five teeth. The peduncle below the flower head is beset with many gland-tipped hairs that appear as tacks. Blooming mostly March and April.

ANNUAL: A spring annual plant with several erect stems reaching sometimes 0.5 meter often growing up and through low shrubs. Absent in dry years. Stem breaks exude milky sap.

LEAVES: Leaves are pinnately divided with long, linear lobes. Leaves at soil level are largest, those above much smaller.

RANGE: In Sonoran Desert at middle and lower elevations but spotty in distribution; absent in some spots and abundant in others. Found from Texas to California.

FRUIT: Mature seeds have a series of slender bristles at the top.


Asteraceae -- Sunflower Family

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Copyright Michael J. Plagens, 1999-2009