40 BULLETIN 479, U. B. DEPARTMENT OF AGRICULTURE. 



should be removed gradually; that is, for an increasing period each 

 day. beginning with exposure for a time during the cooler portion 

 of the morning and afternoon and increasing this until, after 10 

 days or 2 weeks, the shade frames are left off entirely. In Forest 

 Service practice this has not been found wholly necessary. The 

 shades are often left on until the plants become fully hardened. It 

 is certain, however, that the gradual removal of the shade does 

 hasten this ripening process and puts the plants in better condition 

 to withstand frosts. Until the terminal buds are fully formed, the 

 shade frames should be replaced whenever the nights threaten to be 

 frosty. 



WATERING. 



In conjunction with removing the shade frames to prevent 

 damping-off, the watering must also be regulated to induce dryness 

 of the beds. During this danger period no more artificial watering 

 should be practiced than is absolutely necessary to keep the plants 

 in good condition. When it is necessary to water daily, the applica- 

 tion should be as light as conditions will allow and should be car- 

 ried out during the morning hours. When watered in the morning, 

 the beds dry out considerably during the day and do not pass the 

 night in a moist condition very suitable to the development of this 

 disease. 



When there is no further serious danger from this source, the 

 practice followed in watering should change. Soil moisture has 

 more influence upon root development and perhaps upon the mor- 

 tality per cent of seedlings after the damping-off period has passed 

 than any other one factor. In seed beds the plants are crowded, and, 

 unless the moisture in the soil is ample, some of the seedlings are 

 killed out in the competition for water. If there is not enough water 

 near the surface, the roots of those which live go deep in their search 

 for it, and the little-branched, undesirable type of root systems is 

 developed. 



As water is one of the easiest factors to control, any advantage to 

 be gained from its judicious use should be followed up. The aim 

 in watering should be to attain a much-branched root system, with 

 an abundance of fine feeding laterals within the first 10 inches of 

 depth. To secure such roots the soil should be kept fresh near the 

 surface. The kind of soil has an important bearing on the amount 

 of water necessary. In light, sandy, well-drained soils an abundance 

 of water may be used and will increase the root development, but 

 in heavy clay soil excessive moisture seems to decrease the number of 

 fine feeding roots. At the Boulder Nursery, by abundant watering 

 and by maintaining the stands at about 100 per square foot in sandy 



