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.
We have many varied and rich floral colours of singular beauty and attraction to please the eye, elevate the taste, and otherwise charm the fast-declining days of the year - the cultivator having by previous forethought and care produced many subjects wherewith to brighten its retiring hours. Amongst the numerous species of plants suitable for such a purpose, I think the Poinsettia occupies no unimportant position.
Although now very generally grown and utilised for winter decoration, I would endeavour, by giving a few cultural remarks, to establish it in the position which its merits justly claim. Its worth and beauty call for greater attention than has been hitherto accorded it.
The easiest mode of propagation is to take well-ripened shoots of the previous year's growth, with good buds on them, and with a sharp knife form them into "eyes," in a manner similar to that adopted for Vine eyes. Where a large stock is required, wide pots, or, better still, ordinary-sized seed or cutting pans, will be found most suitable: these should be thoroughly well drained, nothing being more essential to healthy vitality than a compost perfectly free from sourness. With good drainage, a compost of fibry loam, leaf-mould, charcoal, and a liberal addition of sharp sand, may be used. Fill the pans to within an inch or so of the top; sprinkle a layer of sand over all. Insert the eyes, leaving their upper extremity merely visible, at a distance sufficient to clear the eyes and admit of easy extraction of the most advanced when potting time arrives. Plunge in a bottom-heat of 80° to 85°, having a surface-heat of 70° to 75°. No water should be given for several days, until the pores are closed, or they will discharge a considerable amount of white acrid matter peculiar to the genus.
The compost not being over-dry, very little more water will be required than an occasional moistening to prevent the sand getting powdery until growth has taken place. Water should be given very carefully, as the eyes suffer in a marked degree from over-dampness.
Eyes put in during March will be fit for potting into small pots in the early part of May, in a compost of loam, leaf-mould, and sand.
In removing the young plants which have pushed before the others, care should be taken to prevent their roots getting broken, they being of a very succulent nature. They should be well shaded from sunshine until established, or drooping heads will be the consequence. With a surface-heat similar to that in which they were rooted, they will speedily fill their small pots, and should be grown on without a check by shifting into 3 and 4 inch pots; and as they root, they may be gradually inured to cooler quarters. Those in the smaller size can be potted into their final 5 or 6 inch pots, using compost of loam, charcoal, and well-decayed cow-manure.
By the beginning of June they will be sufficiently hardened to admit of being grown in an unheated structure. We succeeded admirably, even in Cumberland climate last year, in growing a very large quantity in cold pits, slightly shaded from direct sunshine, and were rewarded with plants clothed to the base with rich dark-green foliage, which the cooler treatment tends to produce, as well as at the same time materially to assist in providing stamina for floral development. They were removed by the middle of September into a gentle heat, pushed gradually on for two months in a minimum temperature of 60°, and were in flower by the beginning of December.
Well-rooted plants introduced to heat will stand copious manure waterings. The quantity should be decreased, and finally withdrawn, ere the scarlet bracts attain full development.
Poinsettias, if grown by themselves, are not much subject to insects, thrips being their chief enemy, which may be got rid of by smoking. They require no syringing overhead - an occasional moistening of the structure being sufficient. When the bracts have been cut, water should still be given - not discontinued, as some do - until the foliage and stems have been properly matured and fitted for a good start next season. In the case of plants intended to be grown in the second year, their shoots may be cut down to within an eye or two of the base, and be kept partially dry until they heal their wounds; but the roots should not suffer for want of an occasional watering, which may be given more freely as the eyes push forth into growth. When they have made a slight start, shake them carefully out of the old soil, and pot them into a smaller size, in a compost of one part loam and one part leaf-mould and sand, using for next and final shift an addition of decayed cow-manure, and treated in all respects as those raised from eyes. For decorative purposes in rooms and halls they are objects of great attraction; as also for vases or table decoration, and for making gay stoves in which foliage-plants predominate.
There are two varieties cultivated in this country - P. pulcherrima and P. p. plenissima, the latter succeeding the former, and keeping up a long succession of flowers. The latter variety has been highly spoken of in influential quarters, but I confess to having neither seen nor as yet grown such splendid examples as certain writers have stated it to be capable of. I do not wish, however, to detract from its reputation, as probably it may not have had exactly the treatment it requires; but grown under the same conditions as P. pulcherrima, I do not consider it so useful as the latter and older variety. R. B.