Xanthium spinosum L.    Asteraceae, (Sunflower Family)   Native, Worldwide   Spiny Clotbur

                                September Photo

Plant Characteristics:  Much-branched, 3-10 dm. high, to 15 or more dm. wide; lvs. lanceolate, entire or few toothed or lobed, 3-8 cm. long, 6-25 mm. wide, subglabrous or strigulose above, silvery-tomentulose beneath, armed with 3-forked stout yellow spines 1-2.5 cm. long in their axils; male fls. rusty-pubescent; invol. of the female heads enclosing the 2 florets and becoming an indurated bur; burs many, but not very crowded, cylindric, ca. 1 cm. long, puberulent, the 2 beaks inconspicuous and unarmed, the body puberulent and beset with numerous uncrowded slender sharply hooked prickles; corolla and pappus none.

Habitat:  Common weed of old pastures and waste places at low elevs., cismontane; to the Atlantic Coast; Santa Catalina and San Miguel Ids.  July-Oct.

Name:  Greek, xanthos, yellow, from the ancient name of some plant, the fr. of which was used to dye hair.   Latin, spina, thorn, spine.  (Jaeger 244).

General:  Rare in the study area having been found only in the canyon northerly of the Newporter Inn.  An immature plant was found in September 1990.  However when I returned to see if it had bloomed, the entire plant was gone and no others could be found.  Fred Roberts at the UCI Museum of Systematic Biology recognized the foliage; so identification was possible.  A fire swept through this entire canyon in late June burning everything down to the edge of the fresh water marsh and even some of that perished.  It has been interesting to watch the new growth of plants along the marsh edge where there is moisture as they, for the most part, started their life cycles several months later than usual.  Many plants have reached maturity and others probably will before it turns cold in late October and November.  (my comments).       There are two seeds in each bur.  They retain their vitality for many years, lying dormant in the thick-walled bur.  This and other species of Xanthium are poisonous to cattle, sheep, horses, hogs and chickens.  They are most poisonous in the seedling stage.  The seeds are also toxic.  The burs cause serious mechanical injury, and lower the value of wool.  (Robbins, et al. 508).       Two species worldwide. (Hickman, Ed. 359).

Text Ref:  Hickman, Ed. 359; Munz, Flora So. Calif. 241.

Photo Ref:  Sept-Jan 90,91 # 5,6,7.

Identity: by Fred Roberts.  

Computer Ref:  Plant Data 410.  

Have plant specimen.

Last edit 10/21/02.  

                                          September Photo