Recent Indiana Weeds 293 



RECENT INDIANA WEEDS/ 



Albert A. Hansen, 



Purdue University Department of Agricultural Extension. 



New weeds appear practically every year in Indiana, usually through 

 the medium of impure seed. Occasionally the newcomers flourish for 

 a while, then practically disappear. Some species, however, make them- 

 selves thoroughly at home and frequently become so aggressive that they 

 are a source of considerable loss and annoyance to the farmer. The 

 great majority of our troublesome weeds are introduced species; for 

 instance, only two of the nineteen species designated as noxious in the 

 Indiana seed law are native plants. 



The species considered in this paper include, (1) plants that are 

 known to be troublesome elsewhere but have not been previously recorded 

 as occurring in Indiana by authorities on the distribution of plants, 

 (2) plants that have not been previously reported as troublesome weeds. 

 This report covers the period from October 1, 1921, to October 1, 1922. 



For verifying identifications, acknowledgment and thanks are due 

 F. V. Coville, A. S. Hitchcock, and S. F. Blake, all of the United 

 States Department of Agriculture, J. N. Rose of the Smithonian Institu- 

 tion and B. L. Robinson of the Gray Herbarium. 



Perennial sow thistle (Sonchus arvetisis L.). Found growing lux- 

 uriantly on the farm of Harry Warr, Brook, Indiana. Mr. Warr con- 

 siders it a "very bad weed with roots that go down three feet." 



The discovery of perennial sow thistle in Indiana is of importance 

 since this species is one of the most troublesome weeds in America, 

 particularly in the Red River Valley of Minnesota and North Dakota 

 and in adjacent Canada. The plant causes greatest damage where a 

 one-crop system of grain farming is practiced, consequently it is not 

 thought that the species can become as troublesome in Indiana on account 

 of the diversified farming practices that prevail. Nevertheless it is a 

 noxious weed that should be guarded against. 



Spotted knapweed (Centaurea macidosa Lam.). A well-established 

 patch of spotted knapweed was found on the Lofland farm near Romney, 

 Tippecanoe County. The occurrence of this species in Indiana is note- 

 worthy since it is a close relative of the black knapweed, Centaurea 

 nigra, considered a serious grassland weed in Europe and recently 

 troublesome in New York. 



Perennial peppergrass or hoary cress. {Lepidium draba L.) Found 

 in LaGrange County. During recent years this species has become 

 extremely troublesome in Utah, California, Colorado and other western 

 states. The following statement is quoted from Bulletin 2(54 of the 

 Colorado Agricultural Experiment Station. 



"Recently the perennial peppergrass has become of such frequent 

 occurrence in Colorado that unless prompt action be taken for its 



'Contribution from the Botanical Department (Extension Division) of the Purdue 

 University Agricultural Experiment Station. 



"Proc. 38th Meeting, 1922 (1923)." 



