Ambrosia psilostachya DC.

=Ambrosia psilostachya var. californica

Asteraceae (Sunflower Family)


Western Ragweed

                                                 July Photo


Plant Characteristics:  Perennial with running underground rootstocks; herbage rather harshly pubescent with short stiff appressed or spreading hairs, glandular, aromatic when rubbed; stems simple, 3-12 dm. high; lvs. mostly only once pinnatifid, 4-12 cm. long, thickish, often subsessile; staminate heads nodding in bractless terminal spikes; staminate invols. scabrous-hirtellous; pistillate heads borne in lf. axils below the staminate spike; pistillate invols. merely tuberculate above or quite unarmed; fruit, a bur less than 6 mm., obovoid, greenish brown, puberulent; spines 0-7 below beak, blunt or vestigial.


Habitat:  One of the very common weeds of roadsides and uncultivated lands, sea level to 2500 ft.; Coastal Sage Scrub, Chaparral, etc. cismontane and in Colo. desert; n. to Wash; Santa Catalina Id.  July-Nov.


Name:  Ancient Greek, also Latin, name of several plants.  Psilostachya is from two Greek words that mean "a bare spike".  (Dale 51).  See A. chamissonis for more on the genus name.


General:  Very common in the study area.  Photographed specimens are from North Star Beach, 23rd Street and Big Canyon. (my comments).     One of the principal, late summer, hay fever plants.  (Dale 51).       A. trifida, which is also found in Calif., has leaves which are reputed to be stimulating, astringent and antiseptic.  (Meyer 125).


Text Ref:  Hickman, Ed. 194; Munz, Calif. Flora 1103; Munz, Flora So. Calif. 112; Roberts 8.

Photo Ref:  June 4 83 # 12; July 2 83 # 19; July 3 83 # 19.


Identity by R. De Ruff.

Computer Ref:  Plant Data 144.

Have plant specimen.

Last edit 9/19/02.


                                 June Photo