14 



berry is a good associate of either. Various cottonwoods may be 

 planted together. Even the trees which will succeed in mixture will 

 grow equally well in pure stands. 



In narrow windbreaks mixtures can be used more freely, since the 

 danger that some species will be shaded out by the others is slight. 

 In street and lawn planting a mixture of rapid-growing trees with 

 slower growing, more permanent ones, is often very desirable. Later 

 the rapid growers can be cut out and the longer-lived trees left to form 

 the permanent stand. 



CULTIVATION. 



Proper cultivation is as essential with trees as with any other crop. 

 Its object is to conserve the moisture content of the soil and to pre- 

 vent the grow T th of weeds and grass. Even if the ground moisture is 

 plentiful, the soil should be stirred to keep it in a pliable, mellow con- 

 dition. On irrigated land it is a good plan to stir the soil after each 

 irrigation. Cultivation should be continued until the trees form a 

 canopy dense enough to completely shade the ground. If the planta- 

 tion is on dry table-lands, cultivation should be continued until the 

 tops form a complete cover. 



Level cultivation should be the sole practice. The method of ridg- 

 ing the dirt up about the trees, sometimes practiced, is very bad. By 

 constant level cultivation a dust mulch is kept up and a minimum 

 amount of surface is exposed. 



The dagger-tooth harrow, the disk harrow, and the five- tooth culti- 

 vator are the best tools to use in cultivating trees. After the trees 

 become too large for using a double harrow a single section of a 

 dagger-tooth harrow, or a one-horse five-tooth cultivator, can be used 

 to excellent advantage. 



Fall cultivation should be avoided, since it tends to stimulate growth 

 out of season and to render the trees susceptible to early fall frosts. 

 On loose, sandy soil cultivation after planting is seldom necessary. 



IRRIGATION. 



The trees should be watered just after they are set out, and as often 

 each season as is necessary to keep the ground moist and soft. Water 

 should be withheld after the 1st of August, for late irrigation, like 

 late cultivation, prevents the wood from properly maturing for winter. 

 Late in the fall or in early winter, when no further growth is possible, 

 it is often a good plan to turn the water on in order to keep the ground 

 from becoming too dry through the winter. Trees constantly give off 

 moisture, and conifers particularly, even in the winter season; unless 

 they can replenish themselves through the roots, death may result 

 from drought. Much loss that is ascribed to freezing is caused in this 

 way. 



[Cir. 109] 



