This section is from "The Horticulturist, And Journal Of Rural Art And Rural Taste", by P. Barry, A. J. Downing, J. Jay Smith, Peter B. Mead, F. W. Woodward, Henry T. Williams. Also available from Amazon: Horticulturist and Journal of Rural Art and Rural Taste.
A Lover of Flowers. In order to get a fine bloom from your plants in winter, you should not allow them to run into rank growth in summer. Do not plunge the pots in the borders, but choose a half shaded spot on the north side of a hedge, paling fence, or low building; the ground firm, and lay three inches of hard coal ashes over it. On this place the pots with room enough for each plant on every side. If the plants are pinched for room, you may shift them into larger pots before hand. Prune the beads of all into good shape, except such plants as have already set their flower buds for next winter, as the Camellia. If the pots are half sunk in coal ashes, (keeping 2 inches of it under them,) it will keep them all the cooler. Water regularly every evening, and in the morning, when the weather is hot and dry. The roots will not run through in the coal ashes, as they do in the soil, and if you give the plants proper attention to watering, you will find they are in excellent flowering condition in autumn, not having exhausted themselves by creeping through the pots, and having their best roots broken at the lifting season.
Before they go into the house in autumn, the roots should be examined - those that want fresh potting should have it, and the others must have the surface of the soil renewed. The greatest error that all novices make in cultivating green-house plants, is in putting them in improper soil. The best and safest compost for all plants, where you are your own gardener, is two-thirds leaf mould, (entirely decayed leaves, to be found in the woods,) and one-third fine sand. Anything will grow in this, and a great many things will not grow without it.