_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, sometimes 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 suffused 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 maybe 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 irrigation once a month until well established. They are not injured by a temperature of twenty-five degrees below freezing and grow both outdoors and in; but with zero weather they require protection. Thornber’s Cholla (_Opuntia Thornberi_) (Named in honor of Professor J. J. Thornber, botanist of the University of Arizona and one of the authors of this book) How to identify and how it grows Thornber’s Cholla is a shrub growing from two to four feet tall, with fantastic branches irregularly whorled and long angular joints six to twenty-four inches in length and yellowish green. It appears waxy, is densely covered with long tubercles or knobs, and has short light-colored spicules. The spines are three to twelve, one-quarter inch or less in length, and very sharp. They are covered with thin straw-colored or brownish yellow sheaths. The flowers of this Cholla are of yellowish and red shadings, appearing mostly at the tips of the branches. The fruit is quite dry when matured and is distinctly tubercled. How to grow Young plants may be set out at any season, also cuttings in spring; they thrive best in rocky or gravelly soil, watered once a month until the plants are established. They grow outdoors or indoors and are not injured by twenty-five degrees of freezing; but at zero they need protection. Spiny Tree Cholla; Tasajo (_Opuntia spinosior_) (The name _spinosior_ means “more spiny,” referring to the many spines of the joints of this species) How to identify and how it grows