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.
Among plants raised annually from seed, for greenhouse or conservatory decoration, the Balsam takes a prominent place as being one of the showiest grown for that purpose. True, it is not a plant very well suited for supplying cut-flowers, neither is it very well adapted for dinner - table work, but it suits very well for mixing among foliage and other plants for general house decoration; and during the time it is in flower, is one of the most effective plants for decorating the conservatory. Few plants will stand a greater degree of hard usage with impunity than the Balsam; or, on the other hand, better repay one for care and attention in its cultivation. Formerly it used to take a somewhat prominent position in our horticultural exhibitions, but for some years it seems to have been quite overlooked: we think this is a pity, as it is just one of those plants most suitable for amateurs and those having small means or limited accommodation for storing plants in winter, and who are yet desirous of having a few flowering-plants, at a small cost, during summer.
It is not always easy to get a really good strain of Balsam seed. It is therefore best for growers to try and save their own seed, when a good strain is obtained, which is very easily done, as the Balsam seeds very freely. The best flowers should alone be reserved for seed-bearing. If kept from moulding, the seed will keep for an almost indefinite time. (It is really astonishing how long some kinds of seed will retain their powers of germinating, if kept under proper conditions. As an instance, last season some Lobelia seed which I bought failed to come up, and I sowed a second time with seed that had been saved in 1877, and I may say that it came up as thickly as Lobelia seed usually does, the percentage being seemingly quite as great as that obtained from fresh seed. It is a well-known fact that seeds lie dormant in the earth for an indefinite time, until the proper conditions are presented to call them into active life. How often has this been exemplified in the making of railway cuttings and embankments, where soil is exposed to the action of light and air which may not have been so exposed for centuries, and yet in a short time they have become covered with verdure, and plants have been known to spring into being which before had not existed in that locality !)
Seed of the Balsam should be sown during the month of February, or early in March, according to the time they may be wanted to flower. Sow in a properly drained pan in leaf-mould and sand, two-thirds of the former to one-third of the latter : cover the seeds lightly, and set the pan in a warm pit or vinery. Cover the pan with a piece of glass until the seed begins to vegetate; but as soon as the seedlings appear, remove the glass and set the pan as close up to the light as may be convenient, in order that the young seedlings may not get drawn up, and weakly in consequence. When they have made two pairs of leaves, pot them off singly in 3-inch pots, as deep as convenient; but in pressing the soil gently, take care not to bruise the stems of the young plants, which at this stage are very tender, else they may damp off altogether. They should still be kept as close up to the glass as possible in order to keep them dwarf and stubby. They will get drawn up a little in spite of all one can do, but this can be rectified at the next potting, which should be as soon as the small pots are well filled with roots; and now they should be shifted into 7-inch or 8-inch pots, using roughish loam, leaf-mould, and sand, with a layer of old manure over the crocks : set the ball of the plant on the top of the manure, and then fill in the soil, pressing it moderately firm about the ball.
A good portion of the stem will thus be buried, which will push out roots, and thus the plant be made dwarfer in habit. If desirable, they may have another shift later on, into 10-inch pots, but this only where larger plants are wanted. The plants will now be pushing out the lateral growths, which should be trained out, either by tying them down to a wire passing round below the rim of the pot, which is the neatest way, or else by hooked sticks pushed into the soil, with the hook passed over the shoot. Their tendency is upwards, so that even though the branches be bent down to a horizontal position, the points will again take the upward direction. The Balsam is a very gross-feeding plant, and therefore requires a good deal of water; and after the pots are filled with roots, they may receive a dose of liquid manure, about twice a-week, with great advantage to the plants. About the middle of May the plants may be transferred to a cool house or pit, always keeping them as near the glass as convenient, but away from draughts. They will begin to flower in July, and continue for a good long time. They are somewhat subject to the attacks of red-spider, but this seldom appears on plants in a healthy condition, and is rather an indication of something being wrong.
It may be kept under, however, by the use of the syringe. J. G., W.