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)