88 WEEDS OF FARM LAND 



because they make the grass patchy by choking it out where- 

 ever they grow. 



(4) Rosette Weeds. The characteristic feature of these 

 weeds is that no leafy stem is produced, but a number of leaves 

 arise together from a rootstock or much compressed stem 

 lying just below the ground level. In some cases, as in the 

 daisy, dandelion, and plantain, the naked flowering stems arise 

 in the same way, but in others, as in shepherd's purse and the 

 various docks, a leafy flowering shoot is thrown up. Two types 

 of rosettes may be distinguished, but the habitat often deter- 

 mines which type will be produced by a particular species of 

 weed. 



(a) Rosettes in which the leaves have little or no leafstalk 

 and the blades are pressed close to the ground, as in daisy, 

 shepherd's purse, hoary plantain, and sometimes the greater 

 plantain. 



(U) Rosettes in which the leaves may or may not have 

 leaf-stalks, but in which the blades are somewhat raised from 

 the ground, forming a cluster rather than a true rosette, as in 

 dandelion, docks, ribwort plantain, and greater plantain (usual 

 form). 



The first type of rosette causes much trouble in grass-land, 

 because all vegetation is choked out from underneath the weeds, 

 and as the latter often occur in large numbers and continually 

 spread, infested pastures rapidly deteriorate in quality unless 

 measures are taken to check the invaders. 



Most of this group are perennial, shepherd's purse being 

 almost the only common annual weed that adopts this habit. 



(5) Weeds Creeping on Surface of Ground and Rooting at 

 Nodes. These weeds closely resemble the trailers (3), but are 

 distinguished by the abundant supply of adventitious roots 

 that are developed from the leaf-joints. Most of them, how- 

 ever, are perennials, as the extra rooting system provides for 

 a continual stock of young plants which are able to establish 

 themselves and survive the winter. Creeping buttercup, silver- 

 weed, and bent grass are representative of these weeds, but the 

 habit is less common than most of the others. 



(6) Weeds Creeping by Rhizomes or Underground Stems and 

 Sending up Green Shoots above Ground. This habit is confined 

 to perennial weeds, and the group includes some of the very 

 worst of the farm weeds. The rhizomes may either creep near 

 the surface as in couch-grass, stinging nettle, corn mint, and 

 rush, or they may descend to various depths, running vertically 



