40 BULLETIN 479, U. S. 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 
