I 



MINIATURE FORTRESSES 147 



outdoors or in; in colder weather than this they should be 

 given protection outside. 



Prolific Tree Cholla (Opuntia arbuscula) 



(The name arbuscula means "a small tree") 



How to identify and liozv it grows 



Arbuscula, or the Prolific Tree Cholla, grows from three 

 to eight feet tall and has a short stout trunk three to six 

 inches in diameter. There are several branches which are 

 intricately arranged, forming a rounded head from six to ten 

 feet across; the gray-brown bark is coarse and fissured. 

 The branch-joints are from two to ten inches long or longer, 

 and are bright green. The light brownish spicules form as a 

 small tuft. Usually only one or two spines are present, some- 

 times none at all, less than two inches long when they occur, 

 bent, slender, needlelike, and a dull straw or brown. The 

 thorns are covered with thin, amber, or brownish, loose, 

 translucent sheaths. The flowers are a greenish yellow suf- 

 fused with red and appear in dense clusters at the tips of the 

 joints; they are produced at the ends of last year's fruit. 

 This often forms a chainlike cycle. The fruit is bright green 

 and nearly smooth. This dwarf tree or shrub grows in the 

 sandy desert areas and flood plains of southern Arizona and 

 adjacent Mexico. 



How to grow 



This cactus spreads from the roots. Young plants may 

 be planted at any season, or branches consisting of several 

 joints may be planted early in spring ; from these, plants grow 

 readily. Also the fleshy fruit develop roots and grow into 

 plants. They thrive best in heavy clay loam with light irri- 

 gation once a month until well established. They are not 

 injured by a temperature of twenty-five degrees below freez- 



