TREES AND SHRUBS 43 



shade trees they are not valuable because the top is small and 

 thin, but used in clusters in connection with conifers, their 

 white stems would be as effective as the birch of the eastern 

 states. They probably would grow at the high levels. 



Willows (Salix t spp.J. Closely related to the cotton- 

 woods and usually associated with them are the willows. 

 There are a number of species native in the State but most of 

 them are but small shrubs bordering the streams and ditch 

 banks. 



Salix bebbiana and 5". scotderiana are two small trees 

 that occur in the timbered mountains at elevations of approxi- 

 mately 7,000 feet. They resemble each other pretty closely in 

 most respects, differing only in the characters of the inflores- 

 cence. They would be of slight value for decorative purposes 

 at middle elevations. 



Salix irrorata and 5". cordata watsonii are two shrubby 

 forms that occur beside streams in the timbered mountains; 

 they would be of use in forming the lower part' of a back- 

 ground or windbreak along an irrigating ditch or stream. 

 Their glossy green leaves, Which are much lighter on the 

 lower surface, are very attractive, and add to their value for 

 decorative purposes. 



The Black Willow (Salix nigra) becomes a tree twenty 

 to thirty feet high in favorable localities and its spreading 

 crown is often broader than it is high. This tree grows readily 

 in sandy soil where the water is near the surface and could be 

 used most effectively for shade and windbreaks about reser- 

 voirs or for shelter belts in the lowest of the valley lands or 

 along ditch banks. It is the common willow tree of the river 

 valleys, being almost as abundant in the Gila valley in New 

 Mexico as is the cottonwood. 



