14 



All our observations indicate that after it is once established the 

 narrow-leaved milkweed tends to remain confined to the ditch banks 

 and adjoining moist areas. There seems to be little danger of its estab- 

 lishing itself throughout the alfalfa fields and meadow hay lands to 

 such an extent that it would cause the hay to be discriminated against 

 for feeding purposes. 



How the Milkweeds Spread. 



The milkweeds produce quantities of flat brown seeds, each of which 

 bears a tuft of shining silky hair by means of which it floats on the 

 wind and is carried to considerable distances. Often they are blown 

 into irrigation ditches and carried to distant fields by the water. 



New patches may start from seeds, or from pieces of roots carried 

 by plows and other farm implements or picked up by the water and 

 transported to new areas. 



Where the plant has become established, the size of the patch is 

 usually increased by the shallow horizontal underground stems which 

 give rise to new plants. 



Figure 5 Root of the Narrow-Leaved Milkweed. 



It is not uncommon for the same root system to connect up a large 

 number of plants, all of which were produced by the spreading hori- 

 zontal roots of a mother plant. Thus when it once becomes established 

 it is indeed hard to get rid of this poisonous weed because of the 

 budding of the roots. In some of the milkweeds such buds are known 

 to form as much as two feet below the surface of the ground ; and a 

 two-inch piece of the root of the common milkweed was found by A. S. 

 Hitchcock in Kansas to be able to form a new plant. On small areas 

 in Nevada the narrow-leaved milkweed has been dug and pulled two 

 or three times during the season without completely eradicating the 

 plant, because of its ability to produce new plants from small pieces 

 of root left in the soil. Thus any means by which the root is broken 

 up into small pieces and left in the ground will enable the plant to 

 maintain itself and in some instances actuallv to increase. 



