BLACK WALNUT: ITS GROWTH AND MANAGEMENT. 19 



affect the growth of the tree, provided the soil conditions are suitable, 

 for the development is good in the irrigated plantations that are 

 scattered through the arid West, and the natural range of walnut 

 extends in Texas into a region of relatively light rainfall. Its de- 

 pendence upon good soil is more marked, however, in regions that 

 have a relatively scant precipitation than it is in well- watered regions. 



TOLERANCE OF SHADE. 



Walnut is decidedly intolerant of shade, although its ability to 

 endure shade varies with site and soil conditions and the age of 

 the tree. During the first few years of its life it will bear consider- 

 able side shading, as is shown in occasional instances in which 

 walnut was planted between rows of corn and grown successfully 

 in combination with corn for two or three years. In mixed hard- 

 wood forests, where there is a lack of light, walnut reproduction is 

 practically never found. It is found on the edges of the forest, 

 along roadways and streams, and in other places where the con- 

 tinuity of the forest cover is broken. In the East, at least, it can come 

 up successfully through brushy tangles of sassafras, sumac, rose, 

 and raspberry bushes, and in between clumps of shrubby willows. 

 In plantations the interlocking of the crowns soon causes a decided 

 reduction of diameter growth; and, after the tree has attained a 

 height of 30 to 40 feet, height growth is no longer stimulated by 

 crowding, the effect of which is, rather, to cut down all increment. 

 Suppressed trees in these conditions become stag-headed and put 

 out water sprouts all the way up and down the trunk. 



REPRODUCTION. 



Black walnut reproduces both by seed and by sprout, the former 

 means being very much the more common. The nut crops are usually 

 generous and the percentage of fertility is high. Transportation of 

 the seed to any distance, however, is practically dependent upon 

 squirrels, and the greater part of the walnut reproduction is undoubt- 

 edly from nuts that are buried by squirrels in open grasslands ad- 

 joining forests. Started under these conditions, the seedlings receive 

 the abundant light needed for their vigorous development. It is 

 doubtful, in fact, whether the seedlings can successfully establish 

 themselves from nuts that are left lying on the surface of the ground 

 or are only lightly covered with fallen leaves. Of the nuts buried 

 in the forest only a small proportion produces successful trees ; most 

 of the seedlings are eventually suppressed by the overhead shade 

 unless they are fortunately located under some break in the forest 

 canopy. This characteristic of walnut reproduction makes it appear 

 likely that in many of the mixed stands containing walnut the walnut 

 was the first to start, originating from nuts buried by squirrels in 



