258 THE FLORIST. 



BOTTOM HEAT. 



As the principles of horticulture, in reference to cultivation, become 

 better understood, there can be no doubt that the application of 

 bottom heaf^ to plants during their period of active growth will be found 

 to be one of the most important auxiliaries the cultivator can employ for 

 assisting his exertions ; and whether the object to be attained be the 

 production of a specimen plant or of our choicer fruits or vegetables, 

 it must be to bottom heat that we shall have to look as affording the 

 best way of accomplishing the end in view. 



When it is considered that most of the fruits, and many vegetables, 

 cultivated at the present day, in gardens even of Umited extent, were 

 originally from countries having a warmer climate than our own, we 

 must at once be open to the conviction that if it is wished to grow them 

 to the full extent of the vigour they are capable of attaining, or to 

 obtain them at an earlier season than they usually come to perfection, 

 we should have recourse to bottom -heat as of the first importance, in 

 producing the rapid development of those parts used as food, whether 

 such may consist of the leaves or of the young or mature fruit of the 

 plants in question ; and we base our arguments on facts drawn from 

 Nature herself 



There are some cultivators who are scarcely aware of the high tem- 

 perature of the soil in tropical chmates ; it is proved by direct observa- 

 tion that a temperature of from 130° to 150° is not unfrequently the 

 case in some places ; and yet this extreme heat is not found to injure 

 the roots of plants indigenous to the soil, but on the contrary, if 

 moisture exist in the stratum below the surface soil, vegetation pro- 

 gresses wdth amazing rapidity. Growers of stove plants in this country 

 know full well that to expose the roots of exotics growing in our stoves 

 to a similar temperature would be attended with certain destruction to 

 their roots ; and this fact serves to show that the constitutional vigour 

 of those plants long subjected to artificial treatment has in this respect 

 become weakened, owing no doubt to the absence of the pure air and 

 complete exposure to light and sun which was the case in their normal 

 condition. Now, although we do not advocate such an extreme artificial 

 bottom heat as we have quoted, for any purpose of cultivation, we allude 

 to it for the purpose of confirming the opinion we have long formed, of 

 the importance of bottom heat to the roots of many exotic plants culti- 

 vated in Britain, in connection with more fully exposing the plants 

 themselves to the open air. 



The temperature of the soil or surface earth in most countries is 

 found to be higher on an average than the air for the greater part of the 

 year. In England the temperature of the air is highest from about the 

 middle of April to middle of August ; the earth having then attained its 

 greatest temperature, parts with its heat slowly, and maintains a higher 

 average by several degrees than the atmosphere. The same may be 

 said of other countries having similar climates ; while in many parts of 



* By the term " bottom heat," it is understood that the temperature of the 

 soil at the roots of plants shall be higher than the atmosphere surrounding them. 



