he forcing of asparagus in various methods has been practiced for centuries, and is rapidly developing into an important industry. The forcing may be done in any place where a temperature of 50° to 60° can be secured, in the greenhouse, hotbed, pit, cellar, or in the garden and field. Whichever plan is pursued, the management of the plants to be forced is the same. The roots should not be less than three years old, and, if obtainable, four or five-year-old plants are to be preferred. These may be dug up from ordinary out-of-door plantations, or, if the forcing is to be done on a large scale and as a permanent industry, the plants have to be grown from seed for this special purpose. To keep up a continuous succession new sowings have to be made every year. The sowing of the seed and the management of the plants during the first year is the same as described in [Chapter V].
The following year, as early as the season permits, the one-year-old seedlings are planted out in rows, to develop as much strength as possible. As the plants are to remain only two years in the nursery bed, they may be placed closer than in a permanent plantation. A distance of two and one-half feet between the rows and one foot in the rows is, however, the narrowest limit, and, where enough ground is available, three by one and one-half or two feet would be still better. By purchasing one-year-old plants a year's time may be gained, but otherwise there are decided advantages in raising one's own plants. During the following two seasons the ground has to be kept in the best possible tilth, and at the end of the third season from seed the roots may be dug just before the ground is likely to freeze. In lifting the roots it is important not to expose them to the drying influence of the sun and air more than is unavoidable. It is also important to preserve the entire clump intact with as much soil adhering to the roots and crown as possible. They are then placed in a shed, pit, or cool cellar, and covered with sand or soil to prevent their drying out. Moderate freezing does not injure the roots, and some growers think that it even adds to their forcing value.
FORCING IN THE GREENHOUSE
With florists the forcing of asparagus has this important advantage: that the income obtained from it is nearly all gain, as the space under the benches, which may thus be utilized, is of but little use for other purposes. If the floor under the benches is soil this is dug out so as to form a pit about a foot deep, or at least a few inches deeper than the clumps are high. Three or four inches of good rich soil is scattered over the bottom, and upon this the clumps are placed close together. Dry, mellow soil is then scattered between and over the clumps, so that the crowns are covered one or two inches, and given a thorough watering. If blanched shoots are desired, the crowns will have to be covered with six or eight inches of soil. The same object may be obtained by shutting off the light, which can easily be accomplished under greenhouse benches. Where it is not practicable to make excavations under the benches, a pit may be constructed by placing boards against the posts and filling in the space thus furnished. To secure a succession, new roots from the reserve stock have to be planted every three or four weeks.
For the first week or ten days after placing the roots in the forcing-pit they should be kept rather cool, so as to give them a chance to become established. A temperature of 45° to 50° is best, at first. Afterward it should be raised to 55° to 60°, and during the day it may rise as high as 80° to 85°. But, as a rule, very high temperatures induce a spindling growth. During the entire forcing process asparagus requires a large amount of water, but unless it has the chill taken off, and ample means for drainage are provided, it may do far more harm than good. The interval between the time of planting and the first cutting varies greatly, according to the temperature and other conditions.
The following are actual dates of asparagus forcing under benches at Cornell University: Plants taken from an old patch November 29th and set under benches three days later. December 4th, shoots just pushing through. December 8th, first shoots cut, averaging nine inches long. December 14th, first good cutting, shoots running from six to fifteen inches long. December 18th, second good cutting. December 26th, a good cutting, some of the shoots having remained too long and become woody; some of these shoots were two feet long. January 10th, a heavy cutting. January 19th, cut about half as many shoots as on the 10th. January 30th, cut about as much as on the 19th, but shoots growing smaller. February 10th, small cutting of weak shoots. Beyond this time there were no shoots worth cutting.
FORCING IN HOTBEDS AND FRAMES
The forcing of asparagus in hotbeds does not differ materially from that in the greenhouse, except in the supply of heat. "A most suitable place for forcing asparagus," writes William Scott, in Garden and Forest, "is a frame about four feet deep with one-fourth inch hot-water pipe running around it. About two and one-half feet of fresh stable litter should be put into the frame and firmly packed, with an inch or two of sand spread over it. This bed should be allowed to stand until the heat of the manure has declined to about 70°, and not below 65°, before the crowns are placed on it. For this work advantage should be taken of a day when the weather is mild, as the crowns are easily damaged by frost. Large crowns five or six years old are preferable to smaller ones for forcing. They may be placed rather closely together in the frame, but the distance apart must be regulated by their size. The roots should be spread evenly over the surface and covered with six inches of sand. Little water will be required, as the steam from the manure affords considerable moisture; but if the bed should become dry, it may be moistened with water of the same temperature as the soil in the frame. A little air may be admitted, when the day is bright and warm, to keep the temperature from rising above 80°. When the points of the shoots begin to appear above the sand the crop is ready to cut. When ground is plentiful, a supply of forcing crowns can be kept up by sowing a little seed every year, having five or six successions, the oldest plants being forced for cutting."
With French gardeners it is customary to plunge the frames in warm stable manure and place the roots directly in the manure, packed as closely together as possible. A mere sprinkling of soil is placed over them. As a result the shoots come up very thick. Only strong, fine three-year-old roots are used, and as many as five crops of roots follow each other through the autumn, winter, and spring in the same frame. Straw mats are used to cover the frames at night.