This section is from the book "The Gardener V1", 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.
There is such a run on dwarf plants of bright colour for table use and other purposes of furnishing in winter, that it is well to remember at the present season how simple it is to accomplish work that may be of paramount value to the gardener during the winter months. About the second week of next month (August) is a good time to take cuttings of Poinsettias, in order to have plants from 1 foot to 18 inches high. The tops should be taken off the strongest plants, or, if there be two stems from the same plant, one may be cut for the purpose indicated, and the other may be allowed to grow on; in any case, the stronger the top is when it is cut over, the finer will be the floral bract - that is, assuming that the cuttings are judiciously managed during the rooting period. The only difficulty in this system of raising dwarf plants is in retaining the foliage during the rooting process. If the tops are strong and vigorous, the leaves are naturally so too, and are liable to fall off immediately if they are exposed to the sun only for a moment, or if they are kept in a low, dry temperature. The practice we adopt is to have a warm bed prepared beforehand, and to insert the cuttings either in small 60-sized pots or into 4-inch pots at once.
If the former course is adopted, the cuttings are inserted at the sides of the pots, in an open mixture of leaf-mould and sand, and plunged at once into bottom-heat, and kept well shaded and syringed until they are nicely rooted, when they are shifted into 4 or 5 inch pots, giving them a strong compost, and shading them for a few days longer to make certain against checks.
If the cuttings are put into 4-inch pots and intended to remain, the pots are filled with a rich, generous soil; and in putting in the cuttings a layer of sand is put at the base of each, to encourage and expedite . the emission of roots, which soon takes place at this season.
After the plants are fairly rooted, they still require careful attention in the way of shading, syringing, and watering, should the weather continue as fickle as it is at present.
They should afterwards be kept on a shelf near the glass, in a temperature not lower than from 55° to 60°, until they begin to show their floral bracts, when they will be considerably improved by plunging them in a bottom-heat of from 75° to 80°, and watered with liquid-manure occasionally. Two years ago we were very successful in raising a large batch of these plants, with bracts varying from 12 to 16 inches in diameter, which rendered us good service in a variety of ways during the winter. Cultivator.