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.
This is about the most generally appreciated winter vegetable we possess, and forcing improves its quality. The plant thrives well on many parts of our sea-shores in pure sand, and this indicates that 'a light soil near the sea is the best. And certainly it is the best, although it can be grown on any good garden-ground, deeply dug and well manured. As in the case of many other sea-shore plants - the Asparagus, for instance - a slight top-dressing of salt occasionally in inland situations where the rains are free from salt, does a great deal of good. Many apply salt to such crops, and finding no benefit to accrue therefrom, come to the conclusion that the use of salt is unwarranted. But in the case of really sea-shore plants, or plants furnishing an appreciable quantity of chlorine and soda or other ash, salt does do good in inland situations; and if care be taken, it will be found that, where no benefit accrues from its use, an appreciable quantity is found in the rains, which come from seaward.
Seakale is raised from seed and from cuttings of the thick fleshy roots of old plants. Having practised both methods, I prefer the first, but shall describe both. Seed can either be sown where the plants are to remain, in the case of permanent plantations, or in beds, as recommended for Asparagus, and afterwards transplanted. I prefer sowing where they are to remain, as a means of saving time. Sow in rows 3 feet apart, and 3 feet between the plants, placing the seeds in this manner .; and when they are up, leave one plant as represented by the dots; and between the rows I take a crop of small growing Cabbages, Turnips, Lettuce, etc., the first season. A winter's mulching of manure, forked in March, prepares them for another year's growth, when they get all the ground to themselves, and, if it be in good condition, they make fine patches for forcing where they stand by means of boxes and manure, as advised for Rhubarb. "When the plants have produced their crop, and the boxes are removed to another lot, the stools are protected with a little litter, and allowed to grow on in summer, to prepare for another year's forcing in the same way, and so on until the plants get unprofitable, when another bed coming on can take their place.
The very last batches can be blanched by merely turning pots or boxes, with all air-holes stopped up, over the stools. Leaves alone, if put thick enough, and firmly beat together, will do very well as a heating material; but care should be taken not to run up the heat too high, or the produce will be drawn and watery - 50° to 60° is quite high enough. Forcing commences in ordinary gardens in November, although in some cases Seakale is cut by November. If the material be right, it will be fit to gather in five or six weeks from the time of covering up; but if it takes eight weeks, no matter. But when time and labour can be spared to make new plantations, the following is a very good way to produce this vegetable during the colder months of the winter: Sow the seed in drills 2 feet apart, on deep, light, well-enriched soil, about the beginning of April. "When the seeds are up, thin to 18 inches apart; and if liberally watered with liquid-manure, they will grow very strong, and be ready to force the first year: but as skill, good soil, good climate, and plenty of manure are necessary for this, perhaps it may be considered rather smart work for an amateur.
So, if the soil and climate and skill be only mediocre, then sow in drills 1 foot apart, thinning to 6 inches in the row, and transplant to the distances above mentioned the following spring, and fine roots for forcing will likely be the result. The forcing in this case is just exactly the same as recommended for Asparagus, by means of a hotbed and frame - only keep perfectly dark; and if the roots be strong, fine Kale will result. In all cases of cutting, cut a thin section of the old crown, for the purpose of keeping the "head" together. It is also forced along with Rhubarb in Mushroom-houses, or as recommended for Rhubarb, in warm cellars, in pots. In propagating from roots, cut the fleshy roots into 10-inch lengths, and transplant them with a dibble, keeping the right end up, and 1 inch below the surface; and if more growths than one result, remove them, leaving the strongest. On thin, poor soils, a slight mulching of rotten manure and occasional soakings of liquid-manure during summer - such as sewage, or farm-yard drainings - will prove of the very greatest service in promoting a strong vigorous growth, which is what should be aimed at if a fine succulent vegetable be wanted.
At a recent meeting of the "Scottish Horticultural Association," Mr L. Dow recommended forcing the Swedish Turnips for a substitute; and having done so for some years, I can also recommend this. Indeed our main supply is got by turning a part of the store (put up in pits for the supply of the cows in spring) from February onward, when the sprouts are to be had in fine condition; and although similar to Seakale, they are prized as a variety of vegetable when others are scarce, and a lesser quantity of Seakale serves. As Mr Dow says, it is certainly economical, for Turnips are easily grown, and, except the shoots forced out, they are not otherwise deteriorated, and remain good cattle-food after being forced. A Gardener.
 
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