36 BULLETIN 24, U. §. DEPARTMENT OF AGRICULTURE. 
of ash and gum are heavier than that of cottonwood, and therefore 
more seed trees are required per acre to insure dense restocking. 
Acorns can not be scattered for any distance by the wind, and there- 
fore natural reproduction of oak can not readily be secured under a 
clear cutting system with seed trees. The best way to encourage 
oak in a cottonwood stand is to preserve young, thrifty immature 
trees wherever they occur. In swamping, or in cutting or deadening 
‘inferior species, the aim should be to save the oaks and free them 
from crowding. Besides forming part of the next cut, they will 
reproduce to some extent. 
One cottonwood seed tree per acre will usually be adequate for 
seed purposes. Where either ash or gum are present the total number 
of seed trees per acre of all species should be from three to four. 
On cut-over areas completely in possession of weed trees it is useless 
to leave cottonwood to reproduce beneath thin shade. Here ash will 
sometimes meet the demand, since it will reproduce under moderate 
shade, but in its absence little can be done to keep boxelder, syca- 
more, hackberry, and other species of doubtful value from taking 
complete possession of the ground. 7 
PREPARATION OF THE GROUND. 
Preparation of the ground in mixed stands should be about the 
same as in pure stands. The shade in mixed stands is ordinarily 
more dense than that in stands of pure cottonwood. Consequently, 
there is hkely to be less underbrush and vines, and slashing of under- 
growth is correspondingly less troublesome. 
In mixed stands, however, the-problem is usually somewhat com- 
plicated by the presence of many inferior trees which have no mer- 
chantable value. Proper ground preparation in these stands will 
entail an outlay for removing or deadening these undesirable asso- 
ciates. Where conditions are favorable to cottonwood reproduction, 
it would hardly seem justifiable to leave scattered inferior species 
merely in the hope that within a few years they may acquire com- 
mercial importance. An expenditure of $2 or $3 at most per acre 
in deadening these trees should result in the establishment of a valu- 
able young cottonwood stand, which otherwise might be indefinitely 
delayed. 
Where. however, the unmerchantable species are very numerous the 
cost of deadening will often be prohibitive and the reproduction of 
cottonwood impracticable. 
Deadening is often a questionable course, in that numerous dead 
trees scattered over an area afford breeding places for insects which 
might later prove injurious to sound trees. Moreover, there is no 
positive assurrance that satisfactory reproduction will follow. It 
