BENEFITS OF MULCHING. 349 



it is designed to accomplish. If it is protection 

 from vicissitudes of temperature during the winter, 

 which is given by the shade, it should be applied 

 late in the fall, after the ground has frozen. If 

 to prevent the ground from becoming too dry, and 

 encouraging the roots to the surface, then in early 

 spring. 



The depth of the material should not exceed two 

 inches. This maintains a regular degree of mois- 

 ture in the soil, and it is thus always in a condition 

 to absorb gases from the atmosphere, which is done 

 more frequently in moist than in dry earths. The 

 experiments of chemists have proved that air, passed 

 through a long tube containing moist earth, loses 

 entirely its ammonia. It also keeps the soil at an 

 equal temperature, and prevents those sudden in- 

 fluxes of sap which cause many species to gum ; 

 the roots derive more fertility, both from their near- 

 ness to the surface, and on account of its porosity. 

 In the autumn it lengthens the season, which the 

 tree requires to thoroughly ripen its wood, and to 

 perfect its fruit-buds ; which it does when the flow 

 of the sap has become sluggish. The soil does not 

 lose its warmth so quickly ; but, when it has once 

 become frozen, the mulching prevents those thawings 

 which stimulate the roots, and which often cause the 

 death of the tree. As the sun has not so much 

 power upon the soil in the spring, the frost comes 

 out slowly, and the buds do not start until all danger 

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