RESULTS OF CULTIVATION. 269 



becoming well aired and oxygenized, as it is under high culture. 

 Under the sod of a lawn, therefore, the roots of trees will be 

 nearer the surface than in ground under cultivation, and will have 

 less power to resist cold, so far as deep roots enable them to re- 

 sist it. 



If a tree is planted in a thoroughly drained soil which is to be 

 cultivated, instead of one which is to be covered with lawn, it may 

 be set several inches deeper, so that the main roots need not be 

 injured by the spade, while they will be kept in warm soil by the 

 occasional turning under of the surface which has been under the 

 direct action of the sun's rays. The roots at the depth of ten 

 inches, in a soil which is spaded annually, and well cultivated, will 

 be as well aired, and have as warm feeding ground, as in a similar 

 soil two inches below an old sod. This cultivation, therefore, gains 

 for the tree a summer and winter mulching of eight inches in depth 

 above its rootlets ; a great gain in winter, and equal to several 

 degrees of more southern latitude. 



Half-hardy trees should therefore not only be planted in ground 

 drained most deeply and thoroughly, but also where the ground 

 may be deeply cultivated until they are rooted in a warm subsoil 

 below the action of frosts say ten years. Trees which even- 

 tually grow to considerable size may, when young, be centres or 

 parts of groups of shrubs that also require high culture ; and when 

 the tree begins to over-top the shrubs, the latter should be gradu- 

 ally removed. But it must be constantly borne in mind that all 

 trees, and especially those of doubtful hardiness, need a full de- 

 velopment of low side-branches when young, and no shrubbery 

 should remain near enough to them to check this side-growth. 

 When all the excess of shrubbery around the tree is removed, and 

 the latter is supposed to have become sufficiently established to be 

 able to dispense with deep culture, and have the ground under its 

 branches converted into lawn, then two or three inches in depth 

 of fresh soil should be added all around the tree, as far as the 

 roots extend ; and for half-hardy trees, an autumn mulching with 

 leaves or evergreen boughs should never be omitted at any age 

 of the tree. The subject of mulching will be treated again in this 

 chapter. 



