50 BULLETIN 24, U. S. DEPARTMENT OF AGRICULTURE. 
a decided profit. Commercial planting in this region, however, 
should be restricted to bottom lands, or, in the case of windbreaks, 
to good farm land. (See Pl. V, fig. 1.) 
The possibility of combining timber growing with windbreak 
planting opens up an important field for cottonwood in the Middle 
West on farm lands too valuable to permit of timber production for 
its own sake. One of the chief requisites in a windbreak tree is rapid 
height growth. Cottonwood meets the requirement better than any 
other species. It is adapted to any good, moist situation, such as 
river bottoms, or even typical farm land of the rolling uplands of 
the eastern portion of the region, where rainfall is comparatively 
heavy. On dry situations, where long droughts are common. a less 
_ exacting tree is better. 
There is, however, a serious objection to cottonwood for wind- 
breaks, due to the sapping effect of its roots upon adjoining crops. 
Tt is generally considered more injurious in this respect than any 
other tree used for windbreaks in this region, and many farmers are 
cutting down groves or belts of cottonwood with no intention of 
replanting it. As a matter of fact, however, actual measurements 
made by the Forest Service show conclusively that in comparison to 
its height cottonwood is the least injurious of any species commonly 
used.# 
The sapping effect of cottonwood, as of any other tree used for 
windbreaks in the Middle West, is almost always more than offset 
by the increased crop yield on the fields protected. Windbreaks in 
this region will usually more than repay the rental for the actual area 
of valuable farm land which they occupy without even taking into 
account the direct financial returns from marketing the wood 
product. 
Since the tree’s foliage is rather open, cottonwood windbreaks 
should be underplanted with a shade-enduring species either as soon as 
the stand begins to open up or else at the outset. For this purpose any 
one of the following trees will do: white or green ash, red oak, box- 
elder, and silver maple. Another method of overcoming this diffi- 
culty would be to plant only two or three rows of cottonwood the first 
year, and to plant additional rows on the side most exposed to the 
sunlight as soon as the original trees show a tendency to become open. 
Two hundred and forty feet has been recommended as the most suit- 
able width for a windbreak belt of cottonwood in this region. 
PREPARATION OF SITE. 
Planting without a thorough preparation of the site is inadvisable. 
On freshly cut-over land the preparation should be practically the 
same as for natural reproduction. Full sunlight is equally indis- 
i Forest Service Bulletin 86, “ Windbreaks.” 
