1256 



FORCING 



FORCING 



be ready to prick off. This operation is tedious and 

 requires deft hands and practice to do it well and 

 rapidly. The plants are separated one from another, 

 care being taken not to injure them, and transplanted 

 into other flats or beds. They are spaced about 2 

 inches apart each way. All diseased and poorly rooted 

 plants are discarded. The number of plants that can 

 be pricked off in a day of ten hours will vary from 5,000 

 to 10,000 according to the skill of the operator. Some 

 of the best growers sterilize the soil in which the seeds 

 are sown and the seedlings grown. This not only 

 insures plants free from disease but eradicates all 

 weeds by destroying the vitality of the weed seed. 



All the care that is required for the seedlings is to 

 keep the planthouse at the proper temperature, see 

 that the soil is supplied with the right amount of 

 moisture, remove all weeds which appear and stir the 

 soil when necessary to keep it from crusting. The 

 house in which the plants are grown should be well 

 ventilated in order to guard against the damping-off 

 of the seedlings. An occasional smudging with some 

 form of tobacco is necessary to keep the green aphis 

 under control. The cabbage butterfly frequently 

 deposits eggs on fall-grown plants and these hatch into 

 green worms which feed upon the lettuce in the beds. 

 The butterflies should be killed when seen flying near 

 the plants and should be guarded against as much as 

 possible. 



In the fall when the days are long and many of them 

 bright, lettuce will be large enough to set in the per- 

 manent beds about four weeks after it is pricked off. 

 When lettuce is sold by the pound it should not be set 

 closer than 7 by 7 inches or farther apart than 8 by 8 

 inches for best results. When sold by the dozen it can 

 be set as close as 5 by 5 inches, although the best dis- 

 tance will depend upon the size of plants which are 

 found most profitable to grow. The first crop of let- 

 tuce will be ready to cut, when sold by the pound, in 

 six to eight weeks from the time the plants are set 

 in the permanent beds. It should give a yield of at 

 least three-quarters of a pound a square foot. 



The prices that the growers have realized for the 

 first cuttings of lettuce have, during recent years, been 

 rather low. The cost of growing this crop is small, 

 however, as little fuel is needed for heating purposes. 

 The second and third crops will require more time for 

 their proper development than the first. They should 

 give a heavier yield, however, and the prices secured 

 are usually better. 



It is very important to have plants of the right size 



to set in the beds as soon as the ground can be prepared 

 after a crop is out. To be able to do this, it is neces- 

 sary to make frequent sowings of seed. In large green- 

 house establishments, seeds should be sown every 

 day or every other day, while in a small forcing-house 

 a sowing should be made once a week throughout the 

 season. No time should be lost between crops as time 

 is money in the vegetable-forcing business. Con- 

 siderable time can be gained by making a second trans- 

 planting for the second and third crops. The plants 

 should be removed from the flats before they begin 

 to crowd and placed in 2-inch pots. These pots should 

 be plunged in the soil between the newly set plants in 

 the permanent beds. The pots should be placed in the 

 beds as thick again as the permanent plants are set. 

 By following this plan, the plants can be grown to a 

 much larger size without injury than is possible when 

 they are grown only in the flats. 



Grand Rapids lettuce will stand a wide range of 

 temperature without serious injury, but the lower the 

 temperature the slower the growth and tougher the 

 leaves, and the higher the temperature the more rapid 

 the growth and more tender the leaves. A low tempera- 

 ture will produce heavy lettuce and a high temperature 

 light lettuce. As long as thorough ventilation is given, 

 little danger of injury from high temperature will 

 occur, but high temperature and closed ventilators 

 invite disaster. The best results are secured when the 

 temperature is held at 45 to 50 at night until the 

 lettuce has attained sufficient height, 8 to 10 inches, 

 when it should be kept as near 45 as possible. The 

 lowering of the temperature at the finishing of the 

 crop will increase the weight considerably. If the 

 houses are arranged so that it is possible to keep but 

 one temperature, a night temperature of 45 to 48 is 

 most satisfactory. The day temperature may vary 

 greatly without injuring the lettuce if the ventilators 

 and heating pipes receive proper attention. Ventilation 

 should be given at all times during the day except 

 when the weather is very cold or stormy. The heating 

 pipes should be turned off whenever the heat from the 

 sun is sufficient to give the proper temperature in the 

 houses. 



Sub-irrigation is the most satisfactory method of 

 watering lettuce. The water can be applied at any 

 time through the tile without wetting the foliage. 

 This method is not in general use because of the ex- 

 pense of installation. Water-tight benches or beds 

 are essential for its successful operation. 



The overhead or Skinner system of watering is in 







1547. A range of forcing-houses. 



