This section is from the book "The Gardener V3", 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.
This valuable greenhouse plant is one of those things which, though of easy cultivation, is nevertheless often to be seen in anything but first-rate condition. Its roots delight in a cool and moist compost, whilst the leaves luxuriate in a medium of coolness and shade. With these conditions secured as nearly as possible, the cultivator ambitious of growing large, well-bloomed plants, has every reason to look for specimens measuring, when in flower, from 2 to about 3 feet across. Supposing some of your readers would like to "try their hand" on growing large plants, the first thing to be done is to sow the seeds by the beginning of April at latest. The compost used must be moist, and composed of three parts loam to one of sand, if the loam is at all strong. Sprinkle the seeds thinly, and just cover them with silver-sand, then either plunge the seed-pot in a very gentle hotbed, or else place it in a pot two sizes larger, filling the space between with sand, which must be kept constantly wet. Place it in a house the mean temperature of which ranges about 60°. Put a square of glass over the seed-pot, to keep the moisture from evaporating, and a handful of Moss on the glass, to keep the rays of the sun from intruding.
In ten days or so the seedlings will be showing themselves, when a little air ought to be let in, increasing it every day till the glass is taken off altogether. Be very careful at this stage of growth to keep the direct rays of the sun from the young plants. Keep them moist by occasionally giving them a gentle dewing with a syringe, and in three weeks they will require pricking off into thumb-pots, using a compost the same as that used for raising the seedlings. A small piece of turf is all that is needful for drainage. Place them somewhere out of the reach of the sun, where they can be kept cool and moist, till they are ready for shifting into larger pots - 4-inch pots are large enough. For drainage use one crock and a little rough turf; pot them firmly. The compost for this and subsequent repottings to consist of five parts strong fibry loam to one of rotted cow-dung, and silver-sand one-sixth of the whole, putting the cow-dung through a ¼-inch sieve. Place them in a cold frame, so situated as to have no sun from eight in the morning till from four to five in the afternoon. Keep the lights off, except in wet weather, and then have plenty of air on, both back and front. Repot into 6-inch pots directly they are well rooted all round the ball, and return them to the cold frame.
By the middle of September move them into an airy pit, and in another fortnight shift them into 8-inch pots. In December repot them finally into 10-inch pots, when it will be only safe to tie each of the shoots to a stake, in case of accidental breakage. Up till the time they are coming into flower they require little in the way of training. The lowermost side-shoots must be broken off for the matter of 3 inches above the soil, and the point of the leading shoot must be taken out three pairs of leaves higher up; pinch them once more in September, and again in December for the last time. With regard to watering, let at least five days elapse after repotting before any water be given (both the ball of the plant and the compost ought to be moist when repotted), afterwards keep constantly moist. Use manure-water made from cow-dung as soon as the blooming-pots are well filled with roots; give it very weak at first, and water with it every time the plant requires watering. By the time the flowers are showing, they will require watering in fine weather twice a-day. Keep on with manure-water till they are done flowering, as, if they are well fed, they will keep developing flowers for a long time.
A look-out must be kept for aphis, and on their first appearance give them a thorough smoking two evenings in succession. If the plants get dry, they will be sure to be infested with greenfly, but even under the best treatment frequent visits from them may be expected. Remove all decaying leaves from them, and do not grow anything else in the pots except the rightful occupants, and they will in return for your pains be a "feather in your cap".
Seed may be sown any time up till August for ordinary greenhouse purposes, and the same general cultural remarks apply to them, differing in greater or less degree according to the time the seed is sown.
R. P. B.