442 
VEGETABLE GARDENING 
Ordinary hotbeds are often used in propagating the 
plants. The amount of manure required depends upon 
the locality. A depth of I foot of fresh manure is usually 
sufficient. The soil is not added until the bed has begun 
to heat. 
In some sections through the northern area of the 
sweet potato district flue-heated beds are employed. 
These are very common in New Jersey. Figure ioi 
shows such a structure with the canvas covering re- 
moved. The canvas is kept over the beds during the 
early stages of rooting and removed later when weather 
conditions permit, but replaced in cold or frosty weather. 
The flues may be built of wood, tile, concrete or brick. 
The walls of the bed are of any desired construction, 
and frequently sash are used for covering instead of 
canvas. 
Pipe-heated beds are popular in some sections. Beat- 
tie (U. S. D. A. Farmers’ Bui. 324, p. 12) gives the fol- 
lowing description of this method : “Where a steam or 
hot water boiler is in use for greenhouse or residence 
heating, a very satisfactory plant bed can be constructed 
by burying four or five lines of pipes in the soil beneath 
the bed and supplying the heat from the boiler. This 
has been found to be an ideal method, as the lines of 
pipes can be controlled by valves and the temperature 
of the soil in the bed kept at the desired point. If hot 
water heat is used the pipes should be laid with the soil 
in direct contact with them, but for steam the pipes 
should be surrounded with 3-inch or 4-inch tiles to pre- 
vent too rapid passage of the heat and the consequent 
burning of the soil. The pipes should be placed 10 or 12 
inches below the bottom of the special soil in the bed, 
and 14 to 16 inches below the line of the seed potatoes. 
If the pipes are laid 18 inches apart, an even distribution 
of heat will be secured. For hot water heating, 2-inch 
pipes should be employed, but 1 3^4 -incli pipes will be 
