12 



WEED FLORA OF IOWA 



Fig. 4-B. Distribution of Smooth Crab Grass. 



Extermination. — This weed is somewhat more difficult to exter- 

 minate than the foxtail, especially in lawns where it is common. 

 Here it produces seed so close to the ground that the lawn mower 

 will not catch this part of the plant. It may, however, be easily 

 destroyed in fields which are cultivated. Stir the soil with a cul- 

 tivator or hoe, exposing the roots to the sun. 



Old Witch Grass (Panicum capillar e L.). 



Description. — An annual with usually coarse, branching stems, 

 1-3 feet long, with very hairy leaf-sheaths and capillary, widely 

 spreading panicles, terminal on the culm or its branches; culm 

 geniculate and branching near the base, rarely simple, generally 

 pilose or pubescent below the bearded nodes; sheaths pilose to 

 densely hirsute, with spreading hairs ; ligule very short, densely 

 ciliate; leaf-blade flat, lanceolate or linear, acute, usually thinly 

 hairy on both sides, margins scabrous and ciliate near the base; 

 hairs throughout spring from small papilla?, those on the leaf-blade 

 being confined chiefly to the principal nerves ; panicle diffuse, 3-12 

 in. long, the branches solitary in pairs, or rarely whorled, the ulti- 

 mate branches and pedicels strongly hispid; spikelets 1 line long, 

 ovate, aeute r or abruptly acuminate-pointed, smooth ; first glume 

 clasping the base of the spikelet, obtuse or acute, 1-3-nerved, about 

 y^ the length of the 5-7-nerved and nearly equal second and third 

 glumes, the acute tips of which are sometimes minutely pubescent ; 

 flowering glume smooth and shining, elliptical, obtuse, or subacute, 

 a little shorter than the larger outer glumes. Variable. July to 

 October. 



