This section is from "The Horticulturist, And Journal Of Rural Art And Rural Taste", by P. Barry, A. J. Downing, J. Jay Smith, Peter B. Mead, F. W. Woodward, Henry T. Williams. Also available from Amazon: Horticulturist and Journal of Rural Art and Rural Taste.
There is no vegetable more readily forced than Asparagus, and there are different contrivances for accomplishing the object. The most perfect mode is, to have one or more beds prepared as above, in a line with, or being a part of, the forcing department for vegetables. The covering for this may be in the form of a low double or single span house, and should be so joined together, that all the sashes can be removed during the summer season. If a regular succession be required from New Year until that in the open ground is ready, it will be necessary, in the Northern States, to have two compartments. In the earliest, heat may be applied about the 1st of December, and in the second, the beginning of February. Of course it is understood here that a common flue, or hotwater pipes, will be needful, and as none but those having large establishments will adopt such a plan, it is expected that a proficient designer would superintend the erection. I may say, however, that the house figured in the January Horticulturist (art. Cucumber), would be most suitable.
Another method is as follows: Excavate a space six feet wide, two feet six inches deep, and as long as may be desired; build up the sides with bricks or stone; erect another wall ("pigeon-hole" fashion) three feet away from the first, so as to leave a cavity of two feet six inches all around, and between the two. There will now be a space of three feet wide in the centre. Fill this up with (first) six inches broken bricks or loose stones; orer which, cover with inverted grass turfs, and the remaining two feet with suitable material for the plants to grow in; plant out in the same way as open ground culture. In two or three years, the plants will be strong enough to force; and when such process is intended, place over the bed a double span, close-boarding frame, one foot high on the sides; fill in the cavity above mentioned with unfermented, but hot stable manure; bank this Up to the sides of the frame, and as it sinks down, add more, so as to keep up the warmth. When the winter milds off, the covering may be removed, and the shoots allowed to grow.
So far, I have only spoken of permanent construction, without regard to expense; but we can go much more cheaply to work, and in a way that will be more generally acceptable, the only drawback being the destruction of the roots afterwards, which, in the other methods, is not the case. In this example, immediately before the frost sets in, dig up a sufficient quantity of strong bearing roots, and cover them with earth, in a cool cellar, to be ready when wanted; or, otherwise, put over the bed enough litter to prevent the ground freezing. As light is not required to develop the sprouts, the roots may be planted in earth, the crowns being covered two inches, and as close together as they can be packed, in a warm cellar, or under the stage of a greenhouse, where a night temperature of 50° to 60° is maintained, which is most suitable for all purposes in forcing this plant. About fifty roots will give -a good dish every three days during four weeks - after which, they become exhausted, and of no further use; consequently, another lot will have to be coming on to meet the deficiency. And it may be further calculated, with the above warmth, that three to four weeks' time will bring the shoots long enough to be cut.
If there be not any other convenience, a common hotbed and box frame will answer the purpose, the making of which has been described in former articles of this series. Care, however, should be exercised as to the bottom heat; for, if too strong, the roots will be scalded, or forced up weakly. Before planting, in this case, cover the surface with turf sod, and pack the roots close, as above stated. When the shoots begin to appear, give as good a supply of fresh air as the state of the weather will admit of, but do not let the thermometer sink below 45°, nor rise higher than 60°.
In the cutting of Asparagus, it has become a common practice to insert the knife below the surface of the ground. So general is this, that it would scarcely sell in the market, unless the lower ends of the shoots were white. Now, the whole of this underground part is tough and stringy, and nothing but fashion's prejudice can tolerate the unnecessary act.