328 



OH O EXPERIMENT STATION: BULLETIN 175. 



Penny-cress. 



136 Penny=cress, French Weed (A) *Thlaspi arvense L. For Ohio, penny- 

 cress is by no means general though promising to become so. It is already 

 common on sandy lands in Lucas and Fulton counties and has also been intro- 

 duced into Delaware and Hamilton counties. It is a persistent, winter annual, 

 flowering and seeding much of the winter and persisting, by means of its seeds, 

 in the land once occupied. The large, broadened, flat pods, about half an 

 inch in diameter, Fig. 24, c, and the other characters given in the illustration, 

 will enable one to identify it. In the valley of the Red River of the North this 

 weed is very abundant and a vile pest. It is there 

 known as French weed. 



Seeds dark brown, 1-16 inch long, flat, egg-shaped 

 without border, striate-roughened with curved lines as 

 in the drawing, Fig. 24, d. Coming in all seeds and 

 grain from the valley of the Red River of the North, and 

 becoming frequent in hay, grain, clover and grass seeds 

 from northwestern Ohio. Penny-cress can best be 

 subdued by continuous cultivation and by smothering 

 with a winter crop, as rye or crimson clover. In case 

 the first plowing is deferred until late in the season the 

 ground should be covered with straw or other combusti- 

 ble litter and burned over to destroy the seed. This 

 applies as well to any of the other weeds of the mustard 

 family mentioned here. 



137 Garlic Mustard (B or P) *Alliaria Alliaria 

 (L.) Britton. This Jack-by-the-hedge has become start- 

 ed in Ohio. It is a coarse weed with large, rounded, coarsely toothed leaves. 

 Destroyed by hoe cutting. 



138 Hedge Mustard (A) ^Sisymbrium officinale (L.)Scop. This is very frequent 

 along roadsides and in waste lands; much less common in cultivated fields than 

 the ones that have been described before. It may be recognized by its spread- 

 ing, ragged growth, two or three feet high, lobed leaves, small, pale yellow 

 flowers and slender, awl-shapel pods closely pressed to the stem. It may be 

 destroyed by frequent mowing or by cultivation and fertilizing. This weed has 

 another bad quality for the grower of cabbage and turnips; it harbors the 

 club-root fungus, Plasmodiophot a Brassicce Wor. These weeds may breed the 

 disease upon land that has never been in cabbage or turnips. 



Seeds light to dark brown, 1-16 inch long by one-third as wide, oblong, 

 cylindrical on back, more or less double- wedgeform and grooved on the other 

 side; found in grasses. 



139 Tumbling Mustard (A or B) ^Sisymbrium altissimum L. Tumbling 

 mustard has come to us by way of the Canadian northwest where it is a very 

 bad weed, liable to be disseminated in baled hay and timothy seed according 

 to Dewey (Circular No. 7, Division of Botany, U. S. D. A., 1896). It is char- 

 acterized by the spreading, mature pods produced in great numbers and the 

 free growth to a height of 2 to 4 ft. The leaves are pinnately divided. The 

 plant has been collected in Lake and Preble counties. 



Seeds small, slightly elongated, 1-32 to 1-24 inch long, approaching in 

 shape those of spreading mustard but smaller. 



140 White Mustard (A or B) *Sinapis alba L. This is easily confused 

 with the two following species. The beak of the pod is flat and the plant less 

 frequent with us. Seeds light colored, spherical, larger than either of the two 



inch in diameter. 



