214 VEGETABLE FORCING 
In the hard coal regions a favorite practice is to use mule 
manure from the mine stables. It is fine in texture and 
contains very little straw, hay or other bedding material. 
108 pest. 
Lines one: 
Fig. 72.—Pot experiment at The Pennsylvania State College showing the value 
of lime for lettuce. 
In the Boston district, the manure is spaded into the 
soil to a depth of 12 to 15 inches or more. This rather 
laborious method is not regarded as necessary by the 
growers of Grand Rapids lettuce. A method which is 
becoming more common every year is to use plows and 
harrows, which may be drawn with one horse. Planting 
the houses in long narrow beds facilitates the use of 
horses in the preparation of the soil. 
Starting plants.—The first sowing of lettuce for the fall 
crop is generally made early in August, though some of 
the largest growers do not sow until about August 20. 
Sowings made August 20 will produce marketable heads 
by the latter part of October or November 1. Lettuce 
maturing before that time does not generally sell readily 
because it must compete with lettuce grown in the open. 
In order to have a continuous succession of lettuce, sow- 
ings should be made at intervals of a week to ten days, 
and larger sowings should be made for the lots which will 
mature at times when there will be an unusual demand, 
as at Thanksgiving and Christmas. 
