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.
If more have been wintered in the hand-glasses than can be left to come to maturity, they should be removed by the middle of March. If the handglasses are of the largest sizes, one plant in each corner and one in the middle may be left, as nice compact early heads are required rather than large ones; but if the glasses are smaller, one in each corner is enough. The surface of the soil should then be well stirred, all dead leaves removed, and a slight earthing-up of a few inches of light rich soil applied. On fine days a free exposure to air must be followed out, shutting them up at night to prevent the soil from losing the heat absorbed by day. They soon make rapid progress, and April adds greatly to their size and strength, and they are generally far ahead of spring-transplanted crops. The glasses should be removed entirely as soon as the plants outgrow them. A top-dressing of well-rotted manure should then be laid over the surface of the ground among and around the plants, and over all a covering of soil. This moulds up the plants and keeps them steady. In performing this operation the corner plants should be pressed away from the centre, to further prevent them from becoming crowded.
This moulding-up must be efficiently and firmly done, so that the plants do not get blown about and loosened at the neck by high winds, and a basin should be left all around them to hold manure-water. When from dry weather it becomes necessary to help them on with water, let it be a thorough soaking once a-week in preference to smaller quantities more frequently. A mulching should be applied after the first watering, and nothing is better for this than old hotbed manure.
In very cold damp situations it is advisable to pot up in October as many plants as are required for the desired number of glasses, in case, in the event of severe weather, they get crippled. In pots they can be wintered in a cold pit or frame, and turned out into the glasses established plants, either to make up blanks or replace the whole stock. These will come away much earlier than transplanted plants, and in cold localities it is always advisable to have a few in pots to make up blanks in the glasses, if not for anything more important; for if the blanks are made up by transplanting, the plants so introduced do not keep pace with the established plants, and eventually get smothered, and of very little consequence.
Returning to the stock of young plants in the seed-beds, the next consideration is to take steps to winter a stock of plants for planting out in good condition in spring, to succeed those under hand-glasses. The means to this end are to a great extent regulated by the climate of different parts of the country. Some localities are so favoured with climate that the Cauliflower can be planted out in quarters like Cabbage, and generally stand the winter so managed. In others less mild it is necessary to prick them off under the shelter of a wall. In the majority of cases it is wise not to trust them without some more substantial means of protection, and it becomes necessary to put a quantity into temporary pits, with some means of covering them up in severe frost, and still better are they under glass in cold frames and pits. For this purpose the latest sowing recommended generally supplies the most suitable plants - the earliest being generally too large, and not in such a good condition to stand the winter, and are more likely to button in spring than less plants. The middle of October is a good time to transplant them into frames, which should stand dry and well exposed. Any moderately-rich soil, such as common light garden soil, answers very well.
The most healthy, stubby, and short-necked plants must be chosen, and planted in rows 4 inches apart each way. They may stand wider if space be plentiful; certainly not closer if fine plants are to be produced.
All the autumn and winter they must be freely exposed to light and air in mild weather, by pulling off the lights every morning and tilting them well up at night. Rain must be kept from them on all occasions, as a superabundance of moisture makes them grow too much, and more liable to suffer from frost. All decaying leaves must be removed when they appear; the surface of the soil kept stirred, and if some charred soil is strewn amongst them, it keeps the surface of the soil from becoming slimy and caked. In dull damp weather, when it becomes necessary to cover them up from severe frosts, it must be borne in mind that they are more likely to be killed by a sudden thaw than by a smart bite of frost. Therefore they should be kept covered up from light after the surface of the soil and plants have become frozen, and not uncovered till they are completely thawed again; and then the covering should be removed, and light and air admitted by degrees. Mice and slugs are the enemies that are to be guarded against, for if allowed their own way they soon spoil a lot of plants - the former by eating the hearts out of them, and the latter by eating the stems below the leaves.
Looking at these Cauliflower plants that have been wintered in frames in cold localities, the next consideration is how to manage them so that they shall succeed those in hand-glasses in a south border. If transplanted into the open borders or quarters in March they receive a considerable check, even when lifted with balls and carefully planted, and are likely to get checked severely by frosts and cutting winds before they get hold of the ground, so that the earliest of them has little chance of being ready by the time the latest under the glasses are cut. To gain the object in view I know of no better plan than that of potting them up out of the frames the first week of February, and establishing them in pots in kindly quarters under glass, for a time at least. In this way they receive a comparatively slight check, and fine strong plants can be turned out with good balls by the end of March. They are also better able to contend with sun and wind, and are much earlier than those transplanted from the frames without being potted.
 
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