26 FARM FORESTRY 



climate tinder which the trees naturally grow, they will not 

 thrive. Seed from trees that grow naturally in northern 

 regions produce trees that do well when planted farther south, 

 because they are less apt to be injured by late frosts in the 

 spring. Southern grown trees coming from a region of 

 longer growing season when planted farther north, do ,not 

 stop their growth in the fall in time to escape the early frosts, 

 and in the spring they are apt to start too early. There are, 

 however, many trees not native to a region which can be in- 

 troduced if found suited to the climate. Many foreign trees 

 do well in this country when they are planted where the climate 

 is similar to that of their native country. 



Light. The amount of light which is demanded by trees 

 varies with different species. Some are able to thrive beneath 

 the shade of other trees, while many demand the full sunlight 

 and grow only in the open. The former are spoken of as 

 tolerant trees, the latter as intolerant trees. Spruce, beech, 

 hemlock and dogwood are examples of tolerant trees. They 

 grow naturally in shady places as on the northern slope of a 

 hill, in a ravine or beneath taller trees. Aspen, jack pine and 

 tulip are examples of intolerant trees. They demand full 

 sunlight for their proper development. If they become over- 

 topped by other trees they will gradually die. Tolerant trees 

 will grow in full sunlight if started in the sun. Some species 

 like the white pine are tolerant in their youth but as the trees 

 grow older they become intolerant and demand full sunlight. 

 The seedlings of all trees will stand more shade than the older 

 trees. Seedlings of many intolerant trees are often found com- 

 ing up in woodlots. These will die later if the older trees are 

 not removed, or if there are not breaks in the canopy allowing 

 the sunlight to pass through. Trees growing under other trees 

 if removed and planted in the sun will die, and trees that have 

 started and grown naturally in the sunlight will die if taken 

 up and planted in shade. Trees are very sensitive to a sudden 

 change in the conditions under which they have lived. 



