INJURIES TO TREES. 107 
forests, and when abundant may do much damage, though on 
account of their comparatively small number they do but slight 
injury. 
Severe Winters. These may injure many kinds of young 
seedlings, which when two or three years old will be perfectly 
hardy. Seedlings of such kinds should be dug at the end of the 
first season’s growth, and be heeled in over winter, or protected 
by a mulch or earth covering in winter. 
Alternate Freezing and Thawing. Secdlings are often 
thrown out of the ground by alternate freezing and thawing, and 
Figure 24. Hravinc out sy Frost. (a) Tree in 
natural position. (b) Drawn up by alternate freezing 
and thawing. 
in this way have their roots broken. This is most likely to hap- 
pen where the ground is bare; if covered with leaves or grass, 
or shaded in other ways, this seldom happens. The best pre- 
ventive is to mulch the surface soil with leaves or other simi- 
lar material, but as mice generally like to live in such places poi- 
son should be used. It should be placed under the mulch, in tin 
