This section is from the book "The Gardener V2", 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 disappointments of past years enhance the value of glass protection for hardy fruits; and the value of walls, unprotected by glass, is lessened to a great extent. Our experience is that walls are very expensive items in the first place, and seldom give good interest for the outlay. Taking all things into consideration, we think walls, in the ordinary sense, should be things of the past. Well-managed orchard-houses give good value every year : they take up little space, are very pleasant objects in gardens, and are of much value for protection to other produce than that of fruits. Most people know this; but I think it an undecided question whether trained trees or those grown in pots are the most productive and give least labour. I would fall in with the trained trees - believing that most fruit can be had from such - arched over about 3 or 4 feet under the glass, and dwarf espaliers along the sides of the structure. If there is a back wall, it of course would be well covered with trees in the usual manner. Some would prefer the pots and small bushes, for the sake of having a great variety; but that wish can be met by the use of cordons - single, double, or triple.
A cordon tree, laden with Peaches, Plums, or Pears, is no mean object; and it does not require much root-cutting or other manipulation to attain this. A firm bed of stones, in which the roots may be partially confined, will keep them free from rank growth, and manure-water can be given ad lib. Wherever I have seen this system of dwarfing trees carried out systematically, abundance of fruit, fine foliage, and very short stiff growths have followed. I have always preferred trees planted out to those in pots. They require less labour, are not so susceptible of injury by root-starving or vice versa, and the expense of pots is saved. Some think that they cannot be kept to size when out of pots, and would not be kept uniform all round. But when they are prepared to remain dwarfs, they can be kept so a great length of time. I managed some trees with the best results that had for a time been in pots, and afterwards planted out in hard ground, ramming the soil firmly all round the roots, like potting a Heath. They became such a nest of healthy roots that they could be lifted and turned round, to prevent one-sidedness, as easily as if they had been in pots. The weight, size, and colour of the fruit were such as I never saw by any other means of culture.