Propagation 67 



are sometimes employed. The cross-brace pieces are 

 more conveniently spaced every 3 feet if sash are used. 

 They thereby act as supports for the sash and facilitate 

 adjusting the ventilation. 



Clean sand is used in the coldframe and the tubers 

 are bedded just as in the open bed method. 



Hotbed, — manure-heated. 



The commercial sweet potato crop of this country is 

 very largely grown from plants produced in hotbeds. 

 This is because the states of New Jersey, Delaware, 

 Maryland and Virginia, which at this time grow the 

 greater part of the crop put on the market, have growing 

 seasons too short to allow the plants to be started in 

 coldframes; because of the increased price which the 

 early crop brings ; and the possibility of growing earlier 

 plants in hotbeds than could be produced otherwise. 

 The tubers are ordinarily bedded six to eight weeks 

 before weather conditions permit the plants to be set 

 in the field. In bedding so early, artificial bottom- 

 heat is necessary to overcome outside temperatures and 

 to obtain a quick growth of large stocky plants. Fresh 

 rapidly fermenting horse-manure, which is naturally 

 bulky and contains a large amount of organic matter 

 capable of creating considerable heat in the process of 

 decomposition, furnishes the cheapest and simplest 

 method of supplying this bottom-heat. In preparing a 

 hotbed, the frame is made in the same way as in con- 

 structing a coldframe, but an excavation must be made 

 for the manure. The depth of the manure will be in- 

 fluenced by the severity of the temperature to be over- 

 come and the length of time heat will be required. The 

 depth usually ranges from 12 to 18 inches. It is better 



