482 STATE BOARD OF AGRICULTURE. 



YELLOW EOCKET. 



Special Bulletin No. 83. 



A Dangerous Weed. 



BY ERNST A. BESSEY^ PROFESSOR OF BOTANY. 



Id the past few years the i)lant known commonly as Yellow Eocket, 

 Winter Cress, Herb Barbara, etc., (Barharea harlarea (L.) MacM.), 

 has assumed a conspicuous place among the serious weed pests of the 

 State of Michigan. The plant is a native of Europe whence it reached 

 America in various ways, chiefly, in all probability, by the contamina- 

 tion of grass and clover seeds with its seeds. It is largely in this man- 

 ner that it has been introduced into Michigan and spread from locality 

 to locality. 



The seeds are produced in Michigan late in May and throughout June. 

 They germinate quickly the same summer and form a low stemless plant 

 with long tap-root and a cluster of shining green leaves. These leaves' 

 are very characteristic in that they are lobed, with a large, round termi- 

 nal lobe and a couple of pairs or so of small lateral lobes. They are 

 free from all hairiness. No upright stem is formed the first season, but 

 as the plant increases in size the crown becomes divided and the roots 

 become greatly branched, losing the tap-root nature. The leaves often 

 remain green throughout the winter if there is a good covering of snow, 

 being uncovered by the European peasants and collected for use as 

 greens on St. Barbara's day, December 4th. When not protected by the 

 snow some, if not all, of the leaves are killed during the winter, but 

 the root remains alive. 



In April, new leaves are produced and soon several to many (5 to 20 

 or so) upright leafy stems shoot up, reaching a height of II/2 fo 2 feet. 

 Each stem may branch considerably, each branch and branchlet being 

 terminated by a cluster of yellow flowers. These are at first crowded 

 closely but as they set seed the branch lengthens so that the slightly 

 four-angled, slender, inch-long pods are scattered along the stems at 

 intervals of % to 1 inch. Each pod produces 10 to 20, mostly about 

 15 seeds. The latter are about the size of clover or timothy seeds. The 

 number of flowers and seeds produced by a single plant is enormous. 

 One well-developed plant, by no means the largest size, possessed over 

 14,000 flowers, which at 15 seeds to a pod means over 200,000 seeds to 

 the plant. 



The seeds begin to ripen about the end of May and continue to be 

 produced for about a month, after which the jjlant dies down. In 

 many cases the roots die, too, but in some cases remain alive and pr.o- 

 duce tufts of leaves and then in the following April send up new up- 



