Frames and Forcing-hills 



343 



in them as they cool^ thus, perhaps, obviating the neces- 

 sity of transplanting to other frames. 



Span-roof coldframes* are useful, as they allow better 

 and more uniform conditions for the growing of plants 

 than the ordi- 

 nary frame. 

 They are cov- 

 ered with hot- 

 bed sash laid on 

 a framework, as 

 seen in Fig. 

 211, and the 

 sashes pulled 



down from the span-root coldframe. 



top for ventilation. They are essentially forcing-houses, 

 however, and the discussion of them is foreign to the pur- 

 pose of this volume. 



Forcing -hills. 



A forcing-hill is an arrangement by means of which 

 a single plant or a single hill of plants may be forced 

 where it permanently stands. It is a small or "indi- 

 vidual " coldframe. 



This type of forcing may be applied to perennial plants, 

 as rhubarb and asparagus, or to annuals, as melons and 

 cucumbers. Fig. 212 illustrates a common method of 

 hastening the growth of rhubarb in the spring. A box 

 with four removable sides, two of which are shown in 

 end section in the figure, is placed about the plant in 

 the fall. The inside of the box is filled with straw or 

 litter, and the outside is banked thoroughly with any 



