36 BULLETIN 475, U. S. DEPARTMENT OF AGRICULTURE. 



SEASON. 



Planting. 



The chief factor governing the choice of the planting season is the 

 climate, and this principally in its relation to the soil moisture at 

 the period of and for a time following the planting operations. 

 Lack of sufficient soil moisture during the period closely following 

 planting and before the stock becomes well established is responsible 

 for a large proportion of the mortality which occurs in plantations 

 on the National Forests. This is particularly true for species natural 

 to the region and normally hardy on similar sites. When planting 

 operations are extensive, it is often necessary to conduct them during 

 both fall and spring because the period suitable for planting is not 

 long enough in either season for their completion. 



SPEING PLANTING. 



Where sufficient rainfall occurs during the spring and early sum- 

 mer months, the spring is almost unquestionably the logical time for 

 conducting planting operations. The soil is in good condition; the 

 planting operations will not normally be hindered for any great 

 length of time by newly fallen snow ; the plants will be in no danger 

 of heaving or winter killing; and they will have a considerable 

 period in which to become partially established before the advent 

 of hot, dry weather. On the other hand, the stock for planting may 

 have started growth in the nursery before the planting site is in a 

 condition to receive it; and labor is more difficult to obtain than at 

 other seasons of the year. 



SUMMER PLANTING. 



Summer is the rainy season in some parts of the country, and as 

 the soil is in the best condition for the growth of plants it might be 

 thought that this would be a favorable time for field planting. Up 

 to the present, however, summer planting has been found to have 

 few points which make it commendable. Under normal conditions 

 trees are in an active growing state during the summer, and the 

 field planting of growing stock is almost certain to meet with failure. 

 It would seem that stock held in cold storage or held back in the 

 nursery by mulching might be planted successfully, but such plant- 

 ings with western yellow pine in Arizona and New Mexico have been 

 unsuccessful on the whole. The trees have usually died during the 

 following fall and winter. Field planting of potted trees during 

 the summer has been partially successful with 1-1—0 * western yellow 



1 The first figure indicates the number of years plants remain in seed beds ; the second 

 figure, the number of years in transplant beds. 



