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.
Seakale is one of our own native plants. It is to be found in many parts of England, Scotland, and the Isles, growing in sandy places close to the sea. It is about 100 years since it first made its appearance in our markets as a cultivated vegetable, although the inhabitants of the shores of England have very long before that time made use of it as a vegetable, taking it immediately after it showed itself above ground in March and April. When cultivated and blanched it has taken a high position among delicate and wholesome vegetables, and there are few gardens of our "better-to-do" classes in which it is not cultivated and esteemed. And really fine Seakale in the depth of winter and early spring is as much worthy of credit as almost any vegetable that can be produced.
The soil in which it is nearly always found growing is next to - often is - pure sand mixed with a little vegetable deposit; and this alone is a guide to its requirements in the matter of soil. Experience has shown that the finest Seakale is grown on deep rather light loams, well manured, and trenched two and three spadings deep. It makes long tap-roots, sending them down deep in search of food, consequently the manure should be mixed with the soil rather deeply, and the same as recommended for Salsafy and other deep-rooting crops. On very light soils a more liberal amount of manure should be given than on those that are more heavy and tenacious. Guano and weak solutions of salt are excellent stimulating manures for it when growing. Thorough drainage is of much importance, and in soils that are clayey and wet should always be carefully attended to. Besides which, it is well worth while to take means of counteracting the tenacity and natural dampness of such soils, by mixing in liberal dressings of either fine old mortar, gritty road-scrapings, or coal-ashes. A still more effectual means is to burn the subsoil and mix it with the better portion of the staple.
By this latter process we have grown the very best of Seakale on soils that have been naturally unfavourable to its growth.
Unless it be in gardens of very moderate extent, and where this vegetable is not forced early, the roots are generally lifted and forced along with Rhubarb in a Mushroom-house, or in dark heated houses or sheds. When to be forced in this way, the most convenient and best way of sowing the seed is in drills 2 feet apart and 2 to 3 inches deep, the first week in March being a good time to sow. To produce first-rate crowns that will force well the first year from seed, the young plants should not be left thicker in the rows than one every 10 inches. From the time the young plants appear, and till they cover the whole ground, the Dutch hoe should be frequently plied amongst them, to keep the surface loose, healthy, and free from weeds.
A very good and generally-practised way of producing Seakale for forcing with one year's growth, is to save the young roots broken off at the time of lifting, and preserve them under a sprinkling of damp soil and some litter till they begin to sprout in spring, when it can more easily be seen which is the top end, and the buds can be reduced to the strongest at the top to form a single crown. These pieces, about 6 inches long, are planted firmly with a dibble the same distance apart as recommended for the growth of seedlings, covering the crown to the depth of an inch or so. During their season of growth all attempts at producing flowers should be prevented by cutting them off as soon as they appear.
Forcing can be carried on in any dark place where the roots can be laid in light rich soil with a temperature of 55° to 60°. Of course, when fine blanched Seakale is required before Christmas, it is desirable and necessary to have a proper place in a Mushroom-house, or along with Rhubarb in a place by themselves. Generally the leaves are easily separated from the crowns by the middle of November, when the necessary number of roots can be lifted and packed firmly in soil over a bed of leaves, which affords a gentle bottom-heat, and causes an earlier and better growth. It is not necessary to preserve the long straggling roots. A foot or 10 inches of the strongest stems, when they are forked, is sufficient. If packed firmly in rows 6 inches apart, and almost as close as they can be put in the rows, a very small space holds a great many roots, and the best way to keep up the supply in good condition is to put in a quantity according to demand every eight or ten days. To blanch it properly absolute darkness is necessary; if a ray of light gets to it when growing, it will colour it, and make it rank in taste.
It is better to begin forcing early, and to do it gently at a moderate temperature, than to delay and force it rapidly, which latter produces weak and comparatively worthless crops.
Seakale can be successfully forced early by packing a number of roots in large pots, plunging them in a bed of leaves with a gentle heat, covering the pot with another of the same size, and throwing some litter and a few old mats over all to completely exclude light. To force after the old-fashioned way with cans and fermenting leaves and stable litter in the open ground is attended with much more labour and trouble; and to pounce upon the crowns that are in the best state for the table is of course not so easy; so that this method is only to be recommended for later crops requiring next to no forcing, and consequently less covering. We have often wondered that farmers who have so good a command of litter do not more generally supply themselves with fine Seakale in the spring months in this way.
Market-gardeners who grow extensively for the market generally force it in trenches 5 to 6 feet wide and 2 deep, where they grow Cucumbers in the summer months. "When the Seakale is ready to lift, they clear out the old material on which the Cucumbers were grown, fill the trenches with stable-manure, and cover it with about 9 inches of light soil, in which to put the roots in rows about 6 inches apart, and as close in the rows as they can lay them. In lifting the plants they break off all the roots, or, as they call them, thongs, carefully saving them for planting for next year's crop, as they rarely ever raise it from seed. All small side-crowns they carefully cut off, which should always be done where they are allowed to grow, leaving just the one main crown, knowing that one good head of Kale is worth more than several slender ones. They cover over the crowns with 8 or 9 inches of straw, then hoop over the trenches, cover with mats, and over all with a good covering of straw. In this way some of the great market-gardeners have been in the habit of forcing well on for 100,000 crowns annually; and simple as are the means, their produce is second to none; but they are in most cases much indebted to their deep alluvial soils, which not many gardens can command.
It is now, however, becoming more common for market growers to force their Seakale and Rhubarb in long heated sheds, which no doubt they find less laborious and more convenient.
Seakale is in its fittest state for using when 7 or 8 inches high. When allowed to grow longer it loses in thickness what it gains in height, and becomes tough and stringy. D. T.