This section is from the book "The Gardener V1", 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.
This choicest of vegetables, unlike French-beans, Seakale, or Mushrooms, in order to be forced with creditable success, requires a long period of preparation of the plant beforehand, although the mere process of forcing is simple enough. Good presentable Asparagus is not such an easy matter to secure, if we take the immense heads usually imported from France as the standard of perfection, and taking the time - four years of good culture - into consideration before it is fit to force from the time of sowing. There are various ways by which Asparagus may be forced, and there are also various ways of growing it for forcing: whichever mode is adopted, one thing is always essential - namely, a well-drained, deep, rich soil. One of the best quarters of Asparagus we have ever seen was a very old one, perhaps a dozen years at least. The subsoil was a pure yellow sand, the soil about 3 feet deep, the surface quite flat. Nothing in the shape of a bed was in the whole quarter, and the seed might have been sown broadcast, so irregular were the plants. This quarter was annually dressed with several inches of rotten hotbed manure, which wasted and got washed into the porous soil with rains. This, with perfect drainage, we believe maintained the vigour of the plantation.
It is not advisable to plant Asparagus, however, in this fashion.
Our favourite plan is to plant in single rows, 3 feet apart and 18 inches from plant to plant: it is convenient for cleaning; gives the roots room to spread, without interlacing or struggling with each other; and although the plants are planted on the flat, an annual top-dressing with manure over the crowns, and the treading between the rows, causes the rows to assume the form of a ridge, which tends to throw the rain off the crowns, and prevent stagnant water at the most vital point: and moreover, to have good Asparagus, it is essential that the early growths are not broken over by high winds. When such is the case, the later growths do not come so strong, and also lose time in coming to maturity. Planting in single rows enables workmen to get easily among the plants, to stake and tie them when necessary. The above distance will be found none too wide to allow strong Asparagus to develop itself. Another point should be attended to when strong Asparagus is grown to be forced, that no seed be allowed to swell on the plants - certainly none allowed to ripen.
No one will think of planting Asparagus without first trenching the ground and manuring it heavily throughout, and more especially in the top spit of soil. In planting, the roots should be spread out horizontally in a circle, it being the most natural position: they radiate in all directions just under the surface, and are ever ready to appropriate nourishment spread over them. The crowns of Asparagus have a tendency to grow out of the surface of the soil, and to have them washed bare with rains. To obviate this, and also to take advantage of it, we have grown the Asparagus in 4-feet beds, sunk 9 inches below the general surface instead of being raised that height, with raised ridges where the alleys should have been. The beds were annually top-dressed in the autumn with good manure, and well supplied with water in summer, and it was decided that they did considerably better than the raised beds: the roots in this way were never laid bare by the rake or by rain.
On heavy soil we have found burnt clay a most excellent dressing to be incorporated with the soil along with the manure, as the trenching goes on. We are at this moment engaged in trenching out an old Asparagus quarter, and find the roots are down plentifully to the depth of nearly 3 feet, which shows the necessity of deep and thorough cultivation. Much stress is often laid on salt as a manure for Asparagus, probably because it is a seaside plant: we have repeatedly tried it, but very much doubt its influence for good or bad, except that it kills for the time any surface weeds. Do the French use salt to produce their colossal heads of Asparagus 1 or is it plenty of room in a rich soil, and particular attention to watering in summer, that is the secret?
Once secure good crowns, and the forcing of Asparagus is a very simple matter indeed. Our own plan is that usually followed, lifting the plants with all the roots possible, and packing them close on a bed of leaves in a heated pit with leaf-mould over and about the roots, care being taken that the heat does not rise too violently. In about a month, the grass will be fit to cut; this is for the earliest lot, put in the end of October. Succeeding beds are made up on the top of the leaves accumulated in autumn, in cold frames: these will come in on about three weeks from starting.
This plan of forcing, however, involves a considerable amount of labour, and space to grow on succession of beds, as at least the same space must be annually planted as is laid vacant by lifting; and as Asparagus is not fit to force until the fourth year, a large breadth of ground must be occupied, which is a serious consideration with many gardeners. To meet this difficulty, the plan is sometimes adopted of building up the sides of one or a series of beds with brickwork pigeonholed, to admit of heat from fermenting leaves and litter placed in trenches on either side of the bed, and covering the bed with cold frames also covered to retain the heat. The same principle is also sometimes adopted, but substituting hot-water pipes in place of the leaves and litter. This last will occupy the least space, and is perhaps the most satisfactory arrangement where expense is no consideration, but we have never had any experience of the plan.
We can, however, confidently recommend a plan the same in principle to the above, but much more simple in working, and which does not so soon exhaust the Asparagus as the hot-water way. It should be carried out in the following manner.
Let the Asparagus be planted with the usual preparation in 4-feet beds of any convenient length, but better if they are not very long, say 30 feet or so, with easy access to each end. After the plants have got strong enough to force, every other bed may be lifted for forcing in pits, the remaining beds to be left for forcing on the ground. To accomplish this dig out all the soil to the depth of 3 feet from the beds which have been lifted, and wheel it upon neighbouring quarters, making the sides perpendicular, which will be easily done, as the soil will be compact and full of roots. There will thus be a bed of Asparagus alternating with a deep trench some 5 feet wide. In the autumn, when forcing commences, leaves can be introduced and trodden into the trenches; and at any part where extra heat is wanted, stable-litter should be mixed with the leaves by turning the latter over.
Two or three 12-feet lengths by 4 feet wide of span-roofed frames, or plant-protectors, are far handier than lean-to frames for covering over the Asparagus; and as one part of the beds is cut and done, the frames can be shifted onwards to fresh pieces of the beds as required, stirring and mixing up the materials in the trench. It is best not to over-cut any part of the bed; it will easily be seen when the Asparagus begins to show signs of weakness, when cutting should cease. When the frame is removed to another piece of the bed, that forced piece should not be left uncovered, but have part of the litter strewn over it to exclude frost. The fermenting material should not be removed the same season it has been used, but allowed to remain, and the Asparagus will root into it and strengthen, and it should be allowed to rest for one year, except a little cutting in the natural way in spring. Every alternate year the material may be removed, when it will be found to be capital leaf-mould, rotten, and fit for any use about a garden where a rich mellow material is wanted. The roots of the Asparagus should be saved, and allowed to hang down by the sides of the trenches, as they will still be of assistance to the plants when forcing begins again.
The space over the leaves need not be left vacant throughout the summer, as, with a few inches of soil thrown over them, crops of Radishes, Lettuces, French-beans, Vegetable Marrows, New Zealand Spinach, or anything the gardener chooses to grow, can be taken off the space. Much attention has been called to a new American Asparagus called Connover's colossal: it remains to be proved whether it is really different from the common. If it proves a large variety under ordinary culture, it will be a decided acquisition. The old variety can be grown to very colossal dimensions, which may be seen any day at this season by walking down the central avenue in Covent Garden market. That there are different varieties of one common sort is certain, as there is in everything grown from seed. Crowns of a dark-reddish colour may be seen anywhere growing side by side with others of a bright pea-green and also intermediate shades, but we believe size entirely depends on culture. Here we find Asparagus does best in a part of the garden where the soil is friable and open, with a moist bottom; where the subsoil is on the gravel, hot and dry, it does not do nearly so well.
The Squire's Gardener.