This section is from the book "The Florists' Manual", by William Scott. Also available from Amazon: The Florist's Manual.
The showy Poinsettia pulcherrima is now botanically classed with the euphorbias, but is still far better known to the trade as poinsettia. It is a native of Mexico and that infers that at no time should it be subjected to a low temperature. Since its introduction it has been a favorite in all collections of hothouse plants, its brilliant scarlet bracts making it unequaled as a decorative plant in the very darkest days of winter. Of late years it has grown greatly in popular favor with our flower-buying patrons and as the lily is now known as the Easter flower, the poinsettia may be and is known as the Christmas flower.
They are often used for decorations when cut with two or three feet of stem, but are more satisfactory in every way when it is possible to use them in pots. When cut the bracts of the poinsettias, as well as the foliage, will often wilt badly and when used for decorating this is very disappointing. This can be prevented to a great extent by putting the stems as soon as they are cut into very hot water. If the ends of the stems are immediately immersed in almost boiling water and before there has been any wilting the flowers and foliage will stand up in good condition. Some growers, to carry out this method faithfully, will carry a pail of hot water around the house with them to receive the stems the moment they are severed from the plants.
Although their fine leaves soon drop in a dry room, the showy bracts remain on the plants for several weeks, always giving the purchaser good value, and as it is one of those plants which we never get returned "to keep for another season" it is satisfactory and profitable to grow, more so than the majority of plants we handle.
Old plants that have rested from January to April or May should be shaken out clean of any old soil, potted into 4-inch, 5-inch or 6-inch pots as their size may require, the shoot or shoots shortened back only to the sound wood. Place in a warm, light house and syringe daily. In four or five weeks there will be a crop of cuttings. In taking off the cuttings leave one young eye at the old stem so that another break will give you another lot of cuttings. As most of your cuttings will go into the sand after you have discontinued firing, there will be no bottom heat; so the cuttings want shade and the sand must have a thorough soaking twice a day in warm weather. In about three weeks the cuttings will be rooted. Lift carefully from the sand and pot into 2 1/2-inch or 3-inch pots. For the first few days, or till the young plants begin to make roots in the soil, keep shaded and moist by frequent syringing. When once they have got hold of the soil they want the fullest light, and in warm months the greatest possible amount of fresh air.
The old plants that you are propagating from can after June 1 be plunged outside, and cuttings taken from outside growth make better plants than those grown inside. You can propagate at intervals till the middle of August, the last cutting struck making fine dwarf plants. We seldom make use of the old plants, but shifted on in September and given plenty of heat and light they will give you a number of medium size flowers. Or if you have a spare bench or bed with six inches of soil, plant out the old stumps. The vigorous growth they will make will surprise you. They will when planted out thrive and flower in a much lower temperature than the plants in pots, but to have in bloom at Christmas they must have 60 to 65 degrees at night. It is well known by all growers of these plants that they will endure 10 degrees lower temperature when planted out where the roots have abundance of room.
The main object in the cultivation of the poinsettia is to obtain a stocky, sturdy plant, retaining all its fine foliage, as dwarf as possible, but crowned with a fine head of what the public calls the bloom. Two shifts are enough; from the 2 1/2-inch to a 4-inch, and from that to their flowering pot, a 6-inch or in later struck plants a 5-inch. Batches of cuttings can be taken off at intervals from May 1 to the end of August, the very latest propagation often making most useful little plants.
A Bench of Poinsettias.
A Pan of Poinsettias.
The poinsettia is very unsightly without its large handsome leaves, and these are too often seen drooping and yellow or entirely absent at Christmas time, just when the plant should be at its best. There are three causes for this: First, a low temperature (60 degrees at night is the lowest they should ever be); second, starvation at the roots, either through an impoverished soil or insufficient root room, and third, as common a cause as any, their roots being disturbed after they begin to form their bracts. A very important point to remember is that they should have their last shift never later than the middle of October and two weeks earlier is better. They cannot endure having their roots disturbed in the least when near their flowering period.
The best soil for them is two-thirds of rather heavy, turfy loam, with one-third of well rotted cow manure, and at the last shift add one pint of bone flour to one bushel of compost. They are very liable to be troubled with mealy bug, which infests their flower umbel proper, but if syringed daily as they should be they are easily kept down. Greenfly also attacks them if regular fumigation is neglected.
If very large bracts on 5-foot to 6-foot stems are desired, you can plant out in six inches of rich soil some thrifty young plants in August. In this way you can get bracts twenty to twenty-four inches across.
Plants unsold, or those you cut for the flower, should be stored away in January either in a warm shed or beneath a bench where not a drop of water will touch them, and allowed to rest perfectly dry till started again the following May. This is an important point. Florists who are strangers to the poinsettia are afraid to let the plants become as dry as is good for them. From New Year's till at least the middle of April the soil in the pots can be dust dry. If you are starting to grow them get plants that have been grown in pots. They will give you better cuttings and more of them than the plants torn up from a bench.
There is a so-called white variety seen occasionally which is certainly not worth growing, and there is a variety named P. pulcherrima plenissima, called the double. It is with me about ten days later than the type, but it is very intense in color, stands travel and handling better and although not making such a wide stretch of bracts is most desirable in every way.
Of late years most of the poinsettias sold as plants are grown in half pots, or as we know them, azalea pots. These pans are more attractive than a single plant in a 5-inch or 6-inch pot. A few small Boston ferns planted in the pans will add immensely to the attractiveness of the arrangement. To make a good pan the cuttings are put in the sand the latter half of August. After the little plants have started to grow in the 2 1/2-inch pots select five or six plants of uniform size and vigor that will insure you a handsome pan. If you put the rooted cuttings from the sand into the pan there might be some failures and blanks.
In concluding this article the subject of which we have been growing for thirty-five years and have known for many more, I must pronounce the poinsettia a very easy plant to grow (a warm house is the only requisite), and one of the most profitable plants we handle, and it is yearly increasing in popular favor.