•62 WEED FLORA OF IOWA 



Distribution. — Nimble AVill was originally confined to southeast- 

 ern Iowa. It has spread northward along the Mississippi, where it 

 is now abundant as far north as Dubuque. It occurs also in central 

 Iowa in Story, Boone and Webster counties and is spreading. The 

 grass is of little economic importance. 



Extermination. — This weed is much more difficult to destroy than 

 the other nimble weeds illustrated. The root-stocks spread more or 

 less horizontally and are large and fibrous. Give a thorough culti- 

 vation, exposing the roots to the sun, and then follow with some 

 leguminous crop. This weed is apt to be abundant in pastures. 

 Here there is no other method of treatment than to get blue grass 

 and white clover into the pasture. 



Mexican Drop-seed Grass (Mulilenbergiamexicana (L.) Trin.). 



Description. — An upright or ascending, usually much-branched 

 perennial 1-3 ft. high, with a scaly, creeping root-stock; numerous 

 flat leaves and contracted, densely-flowered panicles ; sheaths longer 

 or shorter than the internodes, smooth ; ligule ^ line or less long ; 

 leaf -blades 1-3 lines wide, 2-7 inches long; spikelets about 1 line 

 long on very short pedicels ; empty glumes nearly equal, acuminate- 

 pointed about the length of the floral glume (a little shorter or 

 sometimes a little longer) , scabrous on the keel ; flowering glume 

 lanceolate, acute or mucronate-pointed, 3-nerved, pilose near the 

 base and on the callus; palea a little shorter than its glume, very 

 acute. 



Distribution. — Widely distributed in eastern North America, 

 from Canada to Minnesota, South Dakota, Iowa, Nebraska and 

 Missouri. Common everywhere in waste ground in Iowa, espec- 

 ially in Polk, Story, Pottawattamie, Webster, Crawford, Black 

 Hawk, Calhoun. Clinton, Linn, Jasper, Lee and Dubuque counties. 



Extermination. — The character of the "roots" is so different 

 from that of the roots of quack grass and the other perennial weeds 

 that it is not difficult to exterminate. The "roots" of this weed and 

 the allied species are more or less clustered. In an experiment con- 

 ducted to exterminate it we found that by giving a shallow plow- 

 ing of four or five inches and harrowing to expose the "roots" to the 

 sun, they were killed, no growth making its appearance during the 

 rest of the season. Of course this is not effective during rainy 

 weather. 



