26 



cultivated until the trees are large enough to shade the ground. 

 Cultivation should be shallow and frequent, and the ground should 

 not be ridged up around the trees. The drier the season the more 

 the need for cultivation. It is not advisable, however, to cultivate 

 too late in the summer, since the trees may be inordinately stimulated, 

 and their immature shoots injured by early frosts. 



Trees respond very readily to cultivation. This is especially true 

 with such light and moisture-needing trees as cottonwood and green 

 ash. Usually there is a marked decrease in the rate of growth of 

 these trees after cultivation ceases. In groves properly formed, culti- 

 vation should not be necessary or possible after a period of from three 

 to five years. The crowns of the trees should then meet and com- 

 pletely shade out all undergrowth. 



A mulch of hay, leaves, or manure is sometimes applied to young 

 plantations to secure the same results. Such treatment, however, 

 may stimulate the growth of superficial roots. At best it is but a 

 substitute for cultivation and has no advantage over the latter except 

 that it can be applied at any time of the year, while cultivating must 

 be done during the growing season. In every other respect cultiva- 

 tion is preferable. 



Late in fall young plantations of evergreens should be covered 

 with hay or straw from 8 to 12 inches deep. Branches or poles can 

 be used in keeping the straw from blowing off, or, where these are 

 not available, earth can be shoveled here and there upon the straw 

 between the rows. In spring the straw can be taken off. In from 

 three to five years .the crowns of the trees should meet. 



PRUNING. 



Pruning consists in the removal of branches from living trees. It 

 is usually done to secure more shapely trees than could otherwise be 

 had. In groves of proper density this is seldom necessary, as the side 

 branches are shaded out and fall before they reach a large diameter. 

 The degree of natural pruning, however, depends largely upon the 

 kind of tree planted. Light-demanding trees like European larch, 

 cottonwood, black walnut, green ash, and white willow seldom require 

 pruning, while such trees as box elder and silver maple often do. 



With evergreens, pruning should be limited to the dead branches. 

 These can be knocked off, but cutting is best. Whenever it is neces- 

 sary to remove green branches they should be cut off with a sharp 

 knife or hatchet as close to the tree as possible without exposing 

 more of the wood than necessary. If the wounds are large they 



[Cir. 145] 



