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.
The winter and early spring is, at first sight, the period of the year when the forcing gardener is most active; there is, at least, great activity in the stock-hole, and much and anxious communion with the boiler, thermometer, and coal-shovel. But all this activity will avail but little, if the subjects to be forced have not the desired product stored up within their tissues to yield to the forcing.
The sun, it cannot be too often or forcibly insisted on, is the great storer and manufacturer of flowers and fruit. It is not the soil, or water, or manure, and certainly it is not coal or hot water, in winter, that brings success to the gardener. But if a Yine or Strawberry plant has been well charged with the fruit-yielding elements the previous summer, indifferent management in the way of forcing will often result in a fair crop of fruit. As a general rule, all bad setting of fruit at the blooming season is the effect of weakness of the fruit-giving powers of the tree.
Now is the season when the sun is exercising his greatest influence; and therefore now, and for a few more weeks, the gardener who would force with success should be most awake and active. The sun is now maturing our annual supply of bulbs in Holland. All our own early spring flowers are being ripened, and their energies concentrated for another early display. The buds are forming on Azaleas and Rhododendrons, and the early-flowering buds are already formed on the now indispensable Hoteia japonica. It is the sun who is now busy storing up our future early crop of Grapes and Peaches, provided the gardener is doing his part of the work. Now is the time when the forcer must have his wits about him to withhold, assist, and prepare.
The use of the smallest-sized pots in reason for all subjects to be forced in them, is one of the most efficient helps to the proper preparation of forcing plants which the gardener can practise. A small pot helps the sun to mature the plant, by confining the roots and preventing its being over-fed at the same time. If the gardener does his part, the plant will not be starved into ripeness. This applies to Pines, Vines, Stawberries, Roses, or indeed anything to be early forced.
"We believe that a better crop of Strawberries can, with more cer-taint)', be forced out of plants in 4-inch pots than from plants in pots double the size. A highly-fed plant with a large crown, although it looks well in the autumn and winter, generally turns out very prolific of leaves and blind blossoms. But a hard rather stunted-looking plant in a small pot, with scanty crown to the eye, shoots up its flower-spikes with, at first, a seeming scarcity of leaves, but are sure to set, and leaves are sure to follow sufficient to mature the fruit. Then is the time to stimulate and feed the plant, which, in turn, feeds its offspring.
The best finished Grapes in pot-Vines we remember having seen, in size, colour, and quantity - Vines of one year - were grown in 10-inch pots, and stood in large plats of rotten manure, and fed also with liquid. Those Vines were well grown and early ripened in span-roofed pits the previous summer.
"We believe that most gardeners will agree that small pots are the most desirable in which to force all sorts of fruits and flowers; as success does not depend on the size of the pot alone, but on the ripening influence of the sun on a plant - not gorged with rich feeding, as if green leaves were the object. As a seeming contradiction to this, we are also prepared to recommend the use of small pots for the forcing of French Beans and Potatoes in winter and early spring. Pots are better than the open-bed system for the former in mid-winter; and small pots of 8 or 6 inches, and even less, are better than 10 or 12 inch pots, for the same amount of produce can be obtained from the smaller size as from the larger. A large quantity of inert soil is an evil in mid-winter. Better to have the pots well filled with roots, and feed by standing the pots in plats.
"With regard to the forcing of Potatoes, we have proved that a better crop can be grown in small pots of 4 and 5 inches than in large pots of 10 or 12 inches. A single good set planted in a small pot in soil chiefly composed of leaf-mould is much to be preferred to 4 or 5 sets in a large pots; the small pots can be accommodated on shelves near the glass with greater convenience and with less labour, and many shelves will hold the small size which would not take the larger. The chief point is, however, that a better crop is raised in the large pots from the same number of sets. The tops do not run so high in the small pots; they are not so liable to be over-watered and sodden, than which nothing is more mischievous to forced Potatoes. A very small amount of water at the root is really necessary; the young Potatoes will attain a very good size with very little green top. Assist the maturation of the young tubers; it is indeed well known that tubers will form on the old sets under certain conditions without any growth at top at all, so that it is better to have the soil in the pots leaning to the dry side, so as to stunt the growth of the tops, than to encourage them to lengthen.
The same remarks apply to the forcing of Cucumbers in winter; they may be grown with perfect success in pots or in boxes with a small amount of soil, the object being to secure the whole of the soil being perfectly taken possession of by the roots, so that sourness cannot ensue, and feeding by liquid manure becomes almost a necessity.
The earliest crop of Melons will also be found to do best in small pots, or in some way by which the roots may be comparatively confined. Our plan has long been to plant in an inverted Seakale pot placed on a hard bottom, the roots being permitted to escape as the season advances and the plants demand more nourishment.
This is not the time to be discussing the use of small pots in the forcing of vegetables; it is, however, opportune for Strawberries, which we have particularly in view; and the time for potting Dutch Bulbs is at hand. The Squire's Gardener.
[We commend these remarks to the attention of all who are engaged in early forcing. We know that many most successful Pine-growers have this spring failed to get their early plants to start into fruit; they grew into mere leaf instead: and why? owing to the sunless summer of last year. There was not sufficient sun to put fruit into the plants, and no effort could do it this spring. If the dulness of 1872 could have been foreseen, pots half the usual size would have met the case. - Ed].