THE WHORLED MILKWEED AS A POISOITOUS PLANT. 



The natural habitat of Asdepias galioides is dry plains and foot- 

 hills. In the foothills of Colorado and ISTew Mexico it seems best at 

 home in the bottoms of draws. In southern Utah it occurs frequently 

 in sandy, rolling plains. In New Mexico it reaches an altitude of 

 about 7,500 feet and in southern Colorado 7,000 feet. 



Its downy seeds are adapted to wind dispersal, but in the irrigated 

 orchards and fields, where whorled milkweed is becoming abundant, 

 the rapid increase has been due largely to water transportation of 

 seeds. The irrigating ditches have proved to be ideal for the trans- 

 portation, germination, and development of seeds. TMierever ditches 

 have been dug in the neighborhood of whorled milkweed young plants 

 have developed along the water line and spread by means of hori- 

 zontal roots and seeds. The main ditches carry seeds into the 

 laterals and thence into the open fields. Fortunately the milkweed is 

 a sun-loving plant and does not germinate or grow well in the shade. 

 There is little evi- 

 dence that it estab- 

 lishes itself in fields 

 with heavy cover 

 crops like alfalfa, 

 but a poorly seeded 

 field may be just the 

 place for it to get a 

 strong foothold. In 

 old orchards where 

 the milkweed gets a 

 start it r u n s r i o t, 

 often forming a 

 solid mat between 

 the trees. 



The rapidity with which the plant spreads along the ditches is 

 amazing. The orchard country a,t Grand Junction, Colo., has been 

 ditched by various projects, the last and uppermost of which is the 

 United States Reclamation Service ditch. Lateral ditches from this 

 main ditch, dug in new ground but three years ago, are fringed 

 with milkweed. 



In the Grand Junction region much of the stock poisoning is caused 

 by milkweed in the hay. The trees in many milkweed-infested or- 

 chards there have been removed and the land sown to alfalfa. 



Another orchard country, on the North Fork of Gunnison River, in 

 Delta County, Colo,, has no milkweed in its hay, but heavy losses 

 of stock are reported at the time the animals are trailed to and from 

 the summer ranges in the mountains. Ditches and fence rows along 

 these trails often have quantities of milkweed which the stock eat 

 when forage becomes scarce. 



/CiVt 





^^ii 



W 



Fig. 1. 



-Distribution of Asdepias galioides in the United 

 States. 



