120 MISC. PUBLICATION 434, U. S. DEPARTMENT OF AGRICULTURE 



when it may be necessary to raise the temperatures occasionally, the 

 ventilators should be opened during the day when outside tempera- 

 ture is above freezing, and closed at night. 



The best humidity for stock storage is 85 to 90 percent. If lower 

 than 85 is permitted, the stock may shrivel, and if above 90, molds 

 and other storage diseases may spread. Proper moisture content is 

 best maintained by relative humidity of the air rather than by contact 

 with moist packing material. Humidity can be reduced by opening 

 of ventilators or increased by sprinkling the walls and floors with 

 water. A daily check should be made with a wet-and-dry bulb 

 psychrometer or hygrometer to determine the relative humidity. 



Figure 47 illustrates a desirable plan of an inside storage room 

 that can be varied to suit the dimensions of any warehouse. The 

 individual sections are 4 feet long and separated by 2 by 4's. In 

 general, 4-foot, or preferably 6-foot aisles are necessary to permit the 

 workmen to move freely. A space of about 6 feet is allowed between 

 the first tier of stock and outside storage walls, varying with the effec- 

 tiveness of the insulation; but it is best to keep the stock well away 

 from the outside walls, especially in northern States. An 18-inch free 

 space for ventilation should be left between the inside walls and the 

 first tier of stock, also between the adjoining tiers. 



Figure 48 illustrates a convenient method of setting up the tiers 

 for racking the seedlings, patterned after the system in use at the 

 Plumfield Nursery at Fremont, Nebr. Since no nailing is required 

 the racks can be set up readily with no breakage of lumber. The 

 shelving is quickly and easily inserted by means of the shelf hook. 

 The shelves permit the racking of the seedlings from floor to ceiling 

 without excessive pressure at any point and facilitate separation of 

 the various species and grades. 



The seedlings are racked with the roots out and tops in. Tops 

 may be allowed to overlap if aeration is provided, if they are clean of 

 leaves, and if they are not exposed to dripping moisture. 



Although it is not necessary to pack the roots where the storage 

 humidity is properly maintained, they should be protected with a 

 light covering of shingletow or sphagnum moss as a safeguard against 

 fluctuation of temperature and, to some extent, variation in humidity. 

 If the packing material is soaked in water and then allowed to drain 

 before using, it will retain sufficient moisture to make frequent sprink- 

 ling unnecessary in a storage shed where a proper range of humidity 

 is maintained. 



Outside Storage 



Outside heel-in conditions vary widely from north to south in the 

 prairie-plains region. In the southern prairie-plains States, the 

 ground seldom remains frozen for any great length of time and heel-in 

 beds may be opened and stock heeled in or removed as needed, with 

 very little delay because of frozen ground. Farther north, where the 

 ground remains frozen over winter, the stock must be heeled in before 

 the ground freezes and remain in the beds until the spring thaw. 



The essentials of a satisfactory heel-in site are (1) sandy soil, (2) 

 adequate drainage, (3) ready accessibility to an all-weather road, 

 (4) a convenient warehouse or other suitable building large enough 

 for assembling orders and packing out stock for planting. Water, 



