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.
The temperature may average from 40 degrees by night to 60° or 65° by day. The greatest source of disappointment proceeds from injudicious management of the atmosphere. Let it fluctuate similarly to the natural atmosphere; avoid keeping up a midday heat at midnight; always allow a diminution of from 15° to 20° by night over the heat of the day; do not open sashes and admit dry cold winds; air mostly by the top ventilatore, and keep the atmosphere charged at all times with sufficient moisture. Water always in the morning, and have a tank inside the house that the water may he of the same temperature. Never apply water until it is absolutely necessary, and see that it passes freely through the soil; the contrary will indicate deficient drainage.
Much depends upon the arrangement of the plants. There is always a warm end in all greenhouses, where the fire enters, which can be kept up a few degrees above the opposite end. Plants of a tender kind, or those in a growing state, should be placed there: luculias, leschenaultias, epiphyllums, torenias, kalosanthus, etc., comprise some of the former; while heliotropes, primulas, geraniums, roses, Ac., will require warmth to keep them growing and flowering. Ericas, epacris, acacias, hoveas, polygalas, and others such should be kept as cool as possible. Camellias, azaleas, and, indeed, all other plants that are in flower, will require more water than those in a state of rest.
The proper application of water should receive every attention; much depends upon it at this season more especially. Pelargoniums, calceolarias, and cinnerarias should be shifted into larger pots, and kept on the front shelf near the glass, to prevent etiolation of the young stems, which injures their flowering properties. Young plants for the flower garden should be frequently topped (by pinching out the points of the shoots), to render them stocky and strong.
Tropaeolums, a beautiful class of greenhouse climbers, require to be kept rather dry and near light. Mignonette in pots requires to be carefully attended to bring it to perfection; little water and plenty of light will keep it flowering. Keep under cover a supply of soil for potting; that produced from rotted turfs will answer all purposes, using sand, charcoal, or any similar material to maintain a constant porosity. There is no necessity for mixtures of peat and other nostrums, in the way of soil for cultivating plants in pots. The best plant growers are not so particular about the chemical constitution of the soil as its mechanical condition.