50 MINNESOTA WEEDS 



They are covered with small projections, giving the seed a rough 

 appearance. This can be easily seen under an ordinary magnifying 

 glass. White cockle is not very common in this State. Night- 

 flowering catchfly, its close relative, is often mistaken for it. 



White cockle flowers in June and ripens its seeds in July. It 

 is sparsely scattered throughout the State, occurring in grain crops 

 and meadows. The seed is found in red and alsike clover as well 

 as in imported clover and grass seed. 



Eradication. — To eradicate white cockle use a short rotation 

 with cultivated and hoed crops included frequently. A three-year 

 rotation of (1) barley, (2) clover, and (3) corn or potatoes should be 

 effective. Spud out or pull by the roots any stray plants observed. 

 Where thick in meadows, mow early to prevent seed from maturing. 



French Weed (Thlaspi arvense L.) 



Other common names. — Penny cress, stinkweed, field penny 

 cress, bastard cress, mithridate mustard. 



Description. — French weed belongs to the mustard family and 

 is considered one of our worst annual or winter annual weeds. It 

 generally grows from the seed in the spring and produces seeds before 

 the end of the season. Some of the early seeds grow and seed again 

 before frost or else die down, continuing to grow as soon as they thaw 

 out, producing seed early. This plant is often called "stinkweed" 

 because of its disagreeable odor, which is very noticeable. It grows 

 from six inches to two feet high and has white flowers like the flowers 

 of the peppergrass, only they are much larger, about one-sixth of 

 an inch across. The pods are nearly three-fourths of an inch across 

 and much flattened. When the plant is mature, the pods are light 

 yellow in color. The leaves at the ground have petioles or stalks, 

 but on the branches they clasp the stem. The seeds are reddish 

 brown and oval. On the surface of the seed are concentric rings 

 which make the seed very beautiful when examined under the mag- 

 nifying glass. 



The weed flowers almost continuously from early in June until 

 frost, and begins to ripen its seeds in July. It thrives in all kinds of 

 soil, and is rapidly spreading and becoming established in all parts 

 of the State. The seed occurs in millet, clover, cereals, and flax- 

 seed. It is readily separated, however, from the cereals with ordi- 

 nary cleaning apparatus. 



Eradication. — Avoid sowing the seed and prevent plants from 

 maturing. This requires constant attention as some of the plants 

 may mature seeds early in the summer and others at later periods 



