﻿18 BULLETIN 24, U. S. DEPARTMENT OF AGRICULTURE. 



The sprouting capacity of stumps also depends upon their age. 

 After 30 years of age it becomes weak and at 45 years almost ceases. 

 Age, however, does not seem to affect the method of sprouting. Appa- 

 rently the most vigorous sprouting capacity, as determined by the 

 number of sprouts per stump, is somewhere between 15 and 25 years 

 of age. It should be realized, however, that the smaller number of 

 sprouts from stumps below this age is not an indication of lack of 

 vigor, since a small stump can not for physical reasons support as 

 many sprouts as a large one. 



The capacity to sprout, like reproduction from seed, is also gov- 

 erned to a great extent by the light supply. Vigorous sprouts do not 

 develop under the shade of the forest. In stands where only the 

 best trees are cut, coppicing, because of the shade of surrounding 

 trees, is almost sure to fail. 



Another factor of basic importance in affecting coppice repro- 

 duction is the season of cutting. Sprouts readily form after felling 

 in winter or early spring, whereas stumps cut in summer or early 

 fall seldom give rise to thrifty sprout growth. 



The conclusions just given apply particularly to the northern part 

 of the Mississippi Valley in the vicinity of Red Wing, Minn. In 

 the lower Mississippi Valley, where cottonwood is of larger commer- 

 cial importance, very little evidence of this form of reproduction 

 was found. Comparatively few young, vigorous trees are cut. 

 Lumbering usually removes only the larger mature trees, whose 

 sprouting capacity is limited and whose stumps are partially shaded 

 by trees left standing on the ground. Lumbering, furthermore, is 

 usually carried on most extensively in the summer and fall, when 

 the sprouting capacity of the trees is lowest. Probably this combi- 

 nation of circumstances is responsible for the almost entire absence 

 from the lower Mississippi bottom lands of cottonwoods of sprout 

 origin. The adaptability of this system of coppice reproduction to 

 the Mississippi region can be determined, therefore, only after actual 

 experimentation. There is, however, little reason to doubt that 

 young stands of cottonwood in that region can be readily renewed 

 by coppice, provided logging is carried on during the season of most 

 vigorous sprouting and extended also to young trees. 



CHARACTER OF STANDS. 



Cottonwood occurs both in pure stands and in mixture with other 

 species. Either of these conditions is unstable, the pure stand evolv- 

 ing gradually into a mixed one from which the cottonwood may 

 eventually be eliminated. This is due to cottonwood's demand for 

 full sunlight. As the old trees die they are succeeded by stands of 

 more tolerant species which have come up under partial shade. In 

 fact, the very continuance of cottonwood in natural stands seems 



