Mats are essential in the frame culture of early vegetable plants in the North, although double glass sash are used without mats in the milder sections. Mats should be placed on the sash about 4 o'clock in the afternoon in cold weather, and later in the day as the spring advances; but they should not be removed in the morning until the temperature outside is rising, and in very cold weather it may be best not to remove the mats at all from cold frames for a few days or even as long as a week in extreme cases. In March there may be heavy falls of snow with zero weather for many days, with little or no sunshine. Under such conditions it is better not to remove mats. While the plants do not grow when thus excluded from the light, they will not be injured by close confinement at low temperatures.
Fig. 42. Frame Of Hardened Cabbage Plants.
The durability of straw mats depends largely upon care. When deep snow covers the mats, it should be shoveled off before an attempt is made to remove them. When they are wet or covered with an inch or two of snow, the best way to remove them is to walk along the lower side of the frame, grasp the mats at the cords and double them over as far as possible toward the other side. Then go to the upper side of the frame and draw off the mats by taking hold of the lapped-over ends. If wet, they should be spread flat on the ground or, better still, supported on a fence to facilitate drying. To cover the frames in the evening when the mats are wet, proceed as follows: Walk on the mat, reach backward, clasp the far end with both hands, walk over the frame at a crossbar and drop the mat in place. When dry, they are handled rapidly and with ease.
Mats are also useful in shading plants. The glass may be covered entirely in hot weather, or the opposite edges of the mat may be turned back, exposing 6 to 12 inches of glass along each side of the frame. This method of shading is especially valuable when transplanting is done late in the spring.
This process is the firming of the tissues in order that the plants will be able to endure the hardships of transplanting and of open-ground conditions such as freezing, hard drying winds or hot sunshine, any of which may damage or destroy soft, tender plants. Figure 42 shows a frame of well-hardened cabbage plants which when photographed were of reddish-blue color, short and stocky. Such plants will stand a temperature of 12 or 15 degrees above zero.
Plants are hardened by watering sparingly, subjecting them to low temperatures and by providing free ventilation. These operations are equally valuable. When hardening is begun, no more water should be used than is necessary to prevent serious wilting. Air is admitted more freely from day to day. At the end of three or four days the sash may be removed entirely during the day, and the frames closed late in the evening and opened earlier than usual the next morning. Matting is not practiced after a few days more of such treatment and, finally, no protection of any kind is given day or night. This general plan of hardening is primarily for the more hardy plants, as cabbage and lettuce. Tomatoes, peppers and eggplants must be handled more cautiously, although hardening is just as necessary for them. Millions of plants are lost annually because they have not been properly hardened.
As previously stated (202), some plants, as melons, cucumbers, beans and sweet corn, are difficult to transplant because they contain so few fibrous rootlets. It is often an advantage, however, to start them under glass, but their root systems must not be* disturbed to any great extent. This may be accomplished by the use of earthen or paper pots, sods, berry baskets, paper oyster buckets and dirt bands. Earthen pots are highly satisfactory, but are expensive when used in large numbers. Paper pots are becoming popular, and may be made with little expense. Figure 43 shows some pots and the necessary equipment for making them. The operation is very simple. A rectangular strip of paper of the proper size to make the pots desired is folded around a square block bolted through the center to a table. The paper is folded in and clinched in the center with a single upholstering tack driven over the end of the bolt. When planting in the field the paper should always be removed to prevent interference with root development. Melons and cucumbers are often planted on sods. Berry baskets and veneered 4-inch dirt bands, folded into squares, are very useful for starting the above plants.
Fig. 43. Paper Pots And Equipment For Making Them.