2i8 PROPAGATION BY CUTTINGS 



roots are formed to supply food and moisture. Many 

 plants will not root at all without bottom heat. This is 

 supplied out of doors by the natural heat of the soil in the 

 spring and summer, and for some plants, this is often 

 sufficient. With others, however, it is necessary to raise 

 the temperature of the soil by artificial means. In green- 

 house work the soil of the cutting bench is heated by steam 

 or hot-water pipes placed beneath it. Hotbeds are often 

 used, the heat of the soil being raised by the fermenting 

 manure placed below the soil. Frequently cuttings are 

 buried inverted with their bases nearest the surface of the 

 soil. This tends to hold the buds in check and accelerates 

 the rooting. If placed out of doors in the fall or early 

 spring, the ends should be callused and ready for planting 

 by May or early June. 



The air temperature is also important. It is desirable 

 and often necessary to check the growth of tops until the 

 roots have formed. A cutting supplied with warm air soon 

 exhausts the meager amount of food stored in its leaves, 

 and as it cannot well take in moisture until the root hairs 

 have developed, it may wilt and die. It is, therefore, 

 necessary to maintain a low air temperature. In practice 

 this is accomplished by means of shading and ventilation, 

 or by burying cuttings in an inverted position as has been 

 described. 



Uniformity in temperature is very important. The 

 variations between day and night temperatures are not 

 conducive to the most favorable development of cuttings. 

 Under most conditions a soil temperature of 65 F. and an 

 air temperature of 50 to 55 F. is ideal. Frequently, 

 however, the temperature of the soil may be raised some- 

 what higher to hasten the development of roots. 



