The remainder of the walls of the hotbed may be built of wood, cement, brick or stone. The floor beams should be of some rot-resistant wood, such as chestnut, cypress, or whatever it is custom ary to use as posts in the vicinity. The walls may be built of wood by setting posts two or three feet apart and spiking slabs or planks on the out side. A rough floor is laid over the floor beams, four or five inches of soil is put on, and then the roots and the covering are applied in exactly the same way as with the manure hotbed. A cover may be conveniently constructed by placing raf ters eight or ten feet apart and connecting them with the ridge-pole, forming a skeleton roof; over this i3 stretched ordinary unbleached cotton. (Fig. 8-11.) There is no great necessity for heavy cloth such as tents are made of, except that it will last longer. The cotton cloth should be sewed into a single sheet and a roller made by tacking together strips three-fourths-inch by one-and-three-fourths inch, fastening the edges of the cloth between them. The gable end may be of boards or of cloth.
After the potatoes are bedded the cloth tent is put in place and kept there until the plants begin to push through, which should be in about ten days to two weeks. Sometimes a few precocious sprouts will be through in less than a week. After the plants begin to break the soil, attention should be given to ventilating the bed on very hot days. A thermometer should be placed at some average point in the bed, and when the outside temperature is in the eighties, as often happens in the latter part of April or May, the cover should be rolled up, and unless the night is unusually warm it should be lowered at sunset. As warm weather and plant ing time comes on, the cover may be rolled up and the bed kept open to the air the greater part of the time.
After the roots are bedded the bed should be moistened by watering. It is a great mistake to bed the roots in rather dry sand or sandy soil and leave them several days without watering. Moisten ing the soil and the roots starts them into activity and prevents rotting. It is not desirable, however, to keep the hotbed very moist until the plants are up. When the plants are breaking the crust a good watering should be given, or, better yet, the cover should be raised while a spring shower is passing. All experienced sweet-potato-growers agree that no watering is so beneficial to the growing plants az a warm rain. If too much rain is falling, espe cially if followed by a cold wind, the covers may be rolled down as soon as the bed is moistened. As
the plants begin to form leaves and draw heavily on the soil moisture, they will stand a great deal of watering. In fact, up to a certain limit the output of the bed is largely determined by the amount of water given. Too much water makes rank, sappy and tender plants. It is a good plan to keep the bed somewhat dry for two or three days before using the plants for setting out, but serious losses in the next pulling will result if this is carried too far.
When the planting season arrives and the plants are four inches above the ground, making their total length with roots about six to seven inches, the bed may be gone over and all plants of suffi cient size carefully pulled. Usually, when the fin gers are thrust below the soil-line and the plant skilfully pulled sidewise it will come out without dislodging the root. In pulling those plants which are up to size, it is important to disturb as little as possible the root and the other growing plants. As soon as a given area is pulled over, it should be im mediately watered to wet down the disturbed roots and prevent injury to the remaining plants.
An average barrel of seed-roots will cover fifty to sixty square feet of space on the hotbeds. The larger the roots the smaller the space covered, and vice versa. At the first pulling the product of a barrel of roots under favorable conditions will be 3,000 to 5,000 plants, or sufficient for a half-acre or more of ground. As soon as the bed is pulled over, by watering and perhaps adding a little soil and giving the necessary attention, the remaining plants continue to grow and new sprouts are pushed out from the same roots. In this way the bed is ready to pull over again in ten days to two weeks, or perhaps even less time, depending on how closely it was pulled at first. Three pullings are commonly taken from the hotbed during the planting season, but sometimes more. The first pulling is usually regarded as slightly superior to the others.
When plants are grown for sale they are com monly tied in bundles of one hundred, when they may be packed and shipped about the country by express. If they are to be used on the farm, it is a good plan to have a tub of mud batter made by mixing some good clay soil or river mud with water, preferably with the addition of fresh cow dung. The plants are then dipped in bunches of about twenty into this batter and kept in the shade in baskets or trays until they are used. It is nec essary always to set them in a vertical position, or they will curve to the light.