BOTTOM HEAT ITS BENEFITS AND METHODS. 27 



This is because we wish to stimuhite a growth of roots, before 

 the growth of leaves, and to do this we need to keep the soil at ten 

 or fifteen degrees higher temperature than the air over the bed. 

 This relation of temperature of the air to that of the bed is not 

 difficult to maintain in the cool weather of winter and early spring, 

 and as this is the season when we wish to multipl}' our stock of 

 bedding and other plants for spring planting, it is at this season 

 that the gardener finds most use for his cutting bench. When the 

 temperature is kept uniformly at the right point, the rapidity and 

 certainty with which the cuttings root is astonishing. The soft 

 wooded plants will root in about six da^^s and the harder ones in 

 ten or twelve, with a ver}'' small percentage of failures. 



In order to prevent fluctuations in the temperature of the air by 

 the bright sunUght in fine days in spring, it is usual to construct 

 the cutting bench upon the northern side of the greenhouse, with a 

 pai'tition or shade to cut oflTthe direct light of the sun, which would 

 defeat our purpose b}' wilting the tops of the cuttings before they 

 are rooted ; such precautions in avoiding the sunlight are not 

 needed, however, in starting seeds, as young seedling plants have 

 roots enough to endure the heat, if well watered and aired. 



Wherever bottom heat is used the evaporation from the surface 

 of the bed is rapid, and frequent watering is necessary, especially 

 in clear and wind}' weather. This should be attended to at least 

 once a day. 



When plants are hard}', or well established in their roots, and 

 when the temperature of the bed in which the roots grow, and the 

 air above it, are easil}' kept at a proper temperature for the require- 

 ments of the plants to be grown, there will be no advantage gained 

 b}' bottom heat ; but on the contrary it will be found to foster a 

 tender, rapid growth, and the bed will need so much care as regards 

 watering and regulating the temperature, that it is best to do 

 without it whenever practicable. 



The methods in vise for obtaining and applying bottom heat, may 

 be conveniently divided into two classes, depending upon the source 

 of heat, whether from fermenting animal and vegetable refuse, or 

 from fire. 



Where fermenting material is chosen it is most common to make 

 use of horse dung, either alone, or mixed with forest leaves, refuse 

 hops from the brewery, or tan bark from the tan yard. Horse 

 dung, fresh from the stable, is the best material known, and where 



