MISC. PUBLICATION 303, U. S. DEPT. OF AGRICULTURE 



Covillea glutinosa, see Oovillea tridentata. 



Covillea tridentata (DC.) Vail. Creosotebush. 



C. glutinosa (Engelm.) Rydb., Larrea mexwana Moric., L. glutinosa En- 

 gelm., L. tridentata (DC.) Cov., L. tridentata glutinosa Jeps. 

 Range : 9, 10, 11, 16, 17. 

 Site: Dry, sun. 

 Fruit: Capsule. 



A small to large evergreen shrub ; slow growing ; sparsely branched and with 

 thin foliage, especially when older; inhabits the most xeric areas in North 

 America; makes successful and persistent growth in thin bodies of soil over 

 layers of hardpan; transplants ordinarily require considerable water to start 

 them growing ; very inflammable. 



Stomach records: Gambel quail. Observations: Texas antelope squirrel, jack 

 rabbit. Not eaten by livestock ; poisonous to sheep. 



Cowania alba, see Cowania stansburiana. 

 Cowania davidsonii, see Cowania stansburiana. 



Cowania ericaefolia Torr. Heath cliffrose. 



Range: 11, 17. 



Site: Dry, sun. 



Fruit: Achene. 



A small, straggling, much-branched evergreen shrub found on limestone 

 soils. 



Cowania havardii Wats. 

 Range: 11. 

 Site: Dry, sun. 

 Fruit : Achene. 

 A small, much-branched evergreen shrub. 



Cowania stansburiana Torr. Quinine bush. 



C. mexicana dubia Brandeg., C. davldsonii Rydb., C. mexicana stansburiana 

 (Torr.) Jeps., C. alba Good. 

 Range : 9, 10, 11, 13, 14. 

 Site : Dry, well-drained, sun. 

 Fruit: Achene, available in October. 



A small to large shrub or small to rarely large tree ; evergreen ; freely 

 branched, stiff; flowers in June; increased branching occurs under grazing; 

 seed germination 10-80 percent. 



Stomach records: Black-tailed deer. Observations: A staple food of mule 

 deer. An important and valuable browse for cattle and sheep. Browsing to 

 65 percent stimulates beneficially the reproduction of the plant ; more than 80 

 percent causes deterioration. 



Crataegus spp. Hawthorns. 



These species are small shrubs to small trees growing in many sites, in all 

 kinds of soil, in all parts of the country, most of them being almost impossible 

 of identification except by specialists. No effort is here made to separate the 

 various species. Somewhat more than 1,200 species have been listed for the 

 country, the majority of these occurring in the northeastern United States ; other 

 studies have reduced this number to less than 100. Owing possibly to hybridi- 

 zation and great variation, the actual number of species has not been deter- 

 mined up to the present time. Nevertheless, these plants are of considerable 

 value for erosion control and for wildlife food and cover. A great many of 

 them are thicket forming and many species hold the fruit over the winter. Most 

 species are thorny and provide a dense cover valuable for soil and wildlife 

 alike. The best way in which to discover the utility of these species is to 

 examine the wild forms occurring in any particular region and to collect such 

 ones as seem to be able to grow on eroded sites and to produce the maximum 

 amount of cover and food. 



Most species grow in neutral soil, often on very poor soils ; young plants often 

 form long taproots and hence are often difficult to transplant; 6,000-40,000 

 seeds per pound, germination about 40 percent, about 2,500 usable plants per 

 pound of seed ; propagation is by seed stratified and sown in spring ; alternate 

 hosts for the cedar apple rust. 



