NURSERY PRACTICE ON THE NATIONAL FORESTS. 39 



are required to put the slatting on or take it off', and it takes from 7 

 to 10 days per acre (two men from 3|- to 5 days) to complete the 

 operation. The slatting is inconvenient to remove so that small areas 

 under it can not be shaded or uncovered according to the require- 

 ments of the different species. The posts do not readily permit of 

 plowing and harrowing in preparing the ground, so that these oper- 

 ations are more expensive ; and they also interfere in the laying out, 

 sowing, and covering of the beds. Rain collecting on and dripping 

 from low points on these frames washes out either seed or seedlings. 

 The frames do not hold a mulch in place well. At Forest Service 

 nurseries high frames are being used less and less. 



In case of emergencies, brush frames can be used. The principle 

 of these is to use brush to furnish the shade. In high frames addi- 

 tional light stringers may be necessary to support the brush because 

 of its irregular size. For this purpose wire serves very well. Brush 

 frames have some advantages; there is no material quite equal to 

 brush as a light filter; it is cheapest when the nursery is located in 

 a remote region with poor communication by wagon road to a source 

 of lumber supply ; it is more easily removed after a heavy snow than 

 sections of lath roofing; and it can quickly be put up if a special 

 need for shade should suddenly develop at a nursery. On the other 

 hand, it has disadvantages; the leaves and small twigs are continu- 

 ally falling on the plants and must be removed to prevent smother- 

 ing; the brush is very inflammable, and it is not easy to spread, es- 

 pecialty on high frames. Brush when used should be of 'as heavy 

 foliaged species as are available. 



REMOVAL OF SHADE FRAMES. 



The most critical time in growing plants is the 6 weeks follow- 

 ing germination, for during this period they are most subject to 

 damping-off . Shading and watering have an important bearing upon 

 the control of this disease. If germination occurs during cool 

 weather or during hot weather when the surface soil is extremely 

 wet, the shade frames should be removed. As soon as the soil sur- 

 face becomes dry in hot weather, full sunlight is dangerous. It may 

 give rise to " white-spot " injury, regularly confused with damping- 

 off, but caused by overheating the surface soil. The object of the 

 removal of shade frames is to dry the surface soil and lower the air 

 humidity over the beds. This condition is least favorable to the 

 development and spread of the damping-off fungi. 



When practicable, the shades should be removed during periods 

 of rainy weather. The water reaches the soil better and the plants 

 become somewhat accustomed to a greater degree of light. It is 

 generally held that during late summer and early fall the shades 



