Whitethorn is a deciduous shrub, with spiny-tipped twigs, common 

 in the ponderosa pine, mixed conifer, and red fir stands throughout 

 the Sierra Nevadas of California to southwestern Oregon. It is most 

 abundant in the mixed conifer belt. The species grows on a wide 

 variety of well-drained soils, and is usually found in the open, al- 

 though it does well in the shade of coniferous timber. Among its 

 most common associates are greenleaf manzanita (Arctostaph/ylos 

 patula) and common serviceberry (Amelanchier alnifolia), and, at 

 its upper altitudinal limits snowbrush (Ceanothws velutinus) and 

 huckleberry oak (Quercus vo:ccinifolia). 



Whitethorn produces abundant seed and like many members of the 

 g;enus frequently increases after fires or logging, usually in combina- 

 tion with other brush species but sometimes as pure stands. Soil de- 

 terioration from repeated fires or other causes apparently does not 

 check the spread of either whitethorn or its companion species, 

 greenleaf manzanita. Under such conditions these two shrubs, 

 either singly or in combination, become dominant plants. Since 

 whitethorn is one of the first plants to become established on denuded 

 soils, it has immediate value in soil protection, and later serves as 

 a nurse crop for coniferous species. 



While there is some difference of opinion regarding the forage 

 value of whitethorn, its palatability is distinctly inferior to that of 

 many other Ceanothus species. As a rule its browse value ranges 

 from poor to fair for cattle and sheep and from fair to fairly good or 

 occasionally good for goats. Payabilities as high as very good or 

 even excellent are sometimes .reported for whitethorn, especially for 

 goats, but these indicate overgrazed conditions. Usage of whitethorn 

 is often greatly limited because of the general habit of growth in 

 brushfields or dense patches. Plants that are slow-growing, because 

 of age or unfavorable site, are very thorny, have little available for- 

 age, and may even be mechanically injurious. On the other hand, 

 vigorous plants have many new tender shoots that provide good 

 forage. However, the maximum use of whitethorn, even when read- 

 ily accessible, seldom exceeds 20 percent of its foliage. Accordingly 

 stocking must usually be adjusted to facilitate perpetuation of the 

 more palatable species that are grazed in preference to whitethorn. 



The numerous, rigid, many-branched, and spreading stems arise 

 from the base, forming a dense, flat-topped bush 1 to 4 feet high and 

 3 to 9 feet across. The numerous, pale bluish twigs are rigid, spar- 

 ingly leafy, and commonly terminate in a hard sharp point, or 

 "thorn", a characteristic alluded to in the common name whitethorn. 

 The pale green leaves are usually small and more or less elliptical but 

 vary somewhat in both size and shape. The white flowers are borne 

 in small, dense clusters (panicles) about iy 2 inches long and these, 

 in turn, are characteristically massed into larger and very showy 

 flower groups (thyrsiform inflorescence). The small (three-six- 

 teenths of an inch wide) capsule or fruit has three divisions or cells 

 which are easily distinguished when viewed from the top. 



