162 MANUAL OF GARDENING 
manently stands. This type of forcing may be applied to per- 
ennial plants, as rhubarb and asparagus, or to annuals, as melons 
and cucumbers. 
In Fig. 190 is illustrated 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 around the plant in 
the fall. The inside of the box is filled 
with straw or litter, and the outside is 
banked thoroughly with any refuse, to pre- 
vent the ground from freezing. When it is 
Z desired to start the plants, the covering is 
190. Foreing-hill for removed from both the inside and outside 
re of the box and hot manure is piled around 
the box to its top. If the weather is yet cold, dry light leaves 
or straw may be placed inside the box; or a pane or sash of 
glass may be placed on top of the box, when it will become 
acoldframe. Rhubarb, asparagus, sea-kale, and similar plants 
may be advanced two or four weeks by means of this method 
191. Forcing-hill, and the mold or frame for making it. 
of forcing. Some gardeners use old barrels or half-barrels in 
place of the box. The box, however, is better and handier, 
and the sides can be stored for future use. 
Plants that require a long season in which to mature, and 
which do not transplant readily, as melons and cucumbers, may 
be planted in forcing-hills in the field. One of these hills is 
shown in Fig. 191. The frame or mold is shown at the left. 
This mold is a box with flaring sides and no top or bottom, and 
