128 



approached, the ill effects on the species in approximate order are: 



(1) reduction in size of nut. especially with ob- 

 long varieties in length, 



(2) increased jiroportion of faulty kernels, 



(3) increased irregularity of crop. 



(4) practical crop failure, and lastly the 



(5) partial, then complete, destruction of the tree. 



On tlie other hand, the fact that a tree is subject to occasional win- 

 ter injury, or that it bears irregularly, or not at all in a particular site, 

 is not necessarily to be taken that the same tree in a different site or 

 under slightly changed environment would not perform satisfactorily, 

 even in tlie same locality. A change in exposure or of cultural treat- 

 ment, or of rootstock, or of variety, or a modified association of varie- 

 ties, might and frecjuently does bring about entirely different results. 

 Sometimes a southern exposure causes trees to respond to mild weather, 

 in winter or early spring, nnd to be caught by subsequent, ^■iolent droj^s 

 in temperature. Some of the best known and best performing Persian 

 waliuit trees in the East are on a northwestern exposure, yet the spe- 

 cies is commonly not hardy in the temperate portions of this country. 



To a certain extent the ability of orchard trees to withstand frost 

 injury is subject to control. The danger is greatest with trees which 

 have grown late or those which have become devitalized for some rea- 

 son or with those which are in poorly drained soils. The kind of root 

 stock which has been used, is known, to have had an influence in some 

 cases. Doubtless this will be better understood as different stocks are 

 used by the leaders in pecan breeding. Varieties also are known to 

 differ greatly in their degree of hardiness. However, failure ujoon the 

 jDart of otherwise normal trees to bear paying crops with regularity is 

 not necessarilv due to low temperatures. Other factors, such as self- 

 sterility, may be wholly responsible for at least the lightness of crops. 



So far as the orchardist is concerned, a tree is not hardy unless it 

 is capable of bearing crops the average of which are profitable. On the 

 other hand, occisional winter injury does not prove that a species can- 

 not be grown successfully in the same locality. Neither the peach nor- 

 the apple industries of the North nor those of the citrus in the South; 

 and California nor, in fact, any of the other horticultural commodities, 

 of this country are wholly unaffected by frost damage. Our forest 

 trees may be more subject to winter killing than we suspect. A certain 

 amount of winter-injury is to be exiaected in any part of the countrr 

 no matter what the species of plant may be. 



