This section is from the book "The Gardener V3", by William Thomson. Also available from Amazon: The New Organic Grower: A Master's Manual of Tools and Techniques for the Home and Market Gardener.
For making a permanent plantation of Asparagus, the deepest, and, generally speaking, the lightest, soil in the garden should be chosen. A deep sandy loam is the best. Thorough drainage is a matter of great importance, and all ground intended for this vegetable, in which there is the least chance of stagnant water, should be drained to the depth of 4 feet. Wet rots the fleshy roots in winter, and, of course, the produce in spring is correspondingly inferior. A heavy dressing of good manure should be trenched into the soil to the depth of 3 feet, if the staple will allow of such a depth. Deep manuring is of great importance, as the greedy rootlets soon shoot downward to the subsoil. Besides this, another heavy coating of manure should be dug deeply into the ground after the trenching. When these operations are performed, the soil requires to be thoroughly well pulverised, and the manure well incorporated with it. To give young Asparagus a good start, a dressing of rotten leaves forked into the surface of the ground is very beneficial. Thus prepared, it is in readiness for receiving the plants.
In some soils, however, the preparation of the soil for Asparagus is a much more serious affair than I have indicated, which, from its simplicity, is mainly applicable to soils which are light and naturally suitable to the nature and growth of this vegetable.
In heavy clayey soils, if success for any length of time is to be attained, it is sometimes necessary to "force" or make up the soil to a considerable extent, in order to make it sufficiently deep and open. Where the subsoil is very tenacious and wet, it moreover becomes necessary, besides ordinary draining, to bottom the beds with broken stones, brickbats, lime-rubbish, or any open material that will prevent water from collecting about the roots in winter, which is fatal to good Asparagus culture. If the heaviest part of the natural soil can be removed, and light sandy soil substituted, it is very desirable to do so. Under such circumstances, it is a good plan to keep the beds a little above the ordinary ground level, to make doubly sure of escaping the evils of wet underneath. I have burned a large proportion of the soil when it has been heavy, and then mixed it with the best part of the natural soil, adding leaf-mould and manure, and thoroughly mixing the whole together; and in this way have succeeded in growing good Asparagus without bringing in new soils, where it would have been quite impracticable to have grown it without some extraordinary preparation.
But, after all, no matter how carefully the ground is prepared, Asparagus does not succeed so well, under any circumstances, as it does in a soil naturally suited to it; and light deep sandy loams, when well manured, cannot be approached for any length of time by any artificial made-up soil in localities where the soil and subsoil are clayey and wet.
In making plantations of Asparagus, some lay out the ground into 4-feet beds, with paths between about 2 feet wide. In each bed three rows are planted at about 18 inches apart. In preference to this, and for the production of the finest possible samples, the plan of planting in rows, 2 feet 9 inches or 3 feet apart, without forming the ground into beds, is more to be recommended. Apart from this being the simplest way, the extra room afforded gives far finer produce; and the economy of space in the production of so esteemed a vegetable is questionable policy, for one finely-grown head or shoot is preferable to three or four spindly tough ones. Closer planting crowds the tops too much in the growing and ripening season, and, as a consequence, prevents the full development of the crown for another year.
Generally speaking, about the first or second week in April is the best time to transplant from the seedling rows into the ground where it is to remain. About this time it will usually have sprung about an inch; and although it can be transplanted when very much more grown, there is less risk of injury just when commencing to grow, and more chances of its starting into growth without being checked. It is of great importance in lifting the young plants to preserve the roots as entire as possible; and the best way is to take out a trench the contrary way to that in which the lines run, and undermine the plants, and disentangle and remove them with as little breakage as possible. Till planted, they require to be screened from drying sun and winds by throwing mats over them.
I know of no simpler and better way of planting than that of stretching a line along the prepared ground, and cutting close to it on each side in a slanting direction, leaving a ridge like two sides of a triangle on which the young plants are set, with half their roots on one side the ridge and half on the other. The depth to which the cutting on each side of the line must extend is guided by the length of the roots; generally speaking, a foot is sufficient. The French growers of Asparagus, instead of planting on the level, plant in sunken trenches, which, for a climate like France, is no doubt correct practice.
Admitting that the crowns are sprung an inch or more, the depth at which they are placed along the ridge should just be such that the points of the young growths are covered about an inch when the ground is levelled up over them. In heavy damp soils the ridge may be slightly elevated with advantage. This is easily accomplished by placing the plants on the ridge at the level of the soil, and then covering up with the soil which lies between the ridges. Where the soil is at all unfavourable to the growth of Asparagus, it is well worth while to prepare some light rich compost with which to cover the roots and crowns. It helps to start them freely into growth at first.
On light sandy soils it is not advisable to raise the ridges above the level even in this country, for under such circumstances they are apt to suffer from drought, and are not so easily watered when this would be desirable. It is all well in such soils to mulch between and close up to the rows with dung or partially-decayed leaves. This, in case of early summer drought, will protect the roots, and render watering more beneficial when applied.