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.
Considering the usefulness of the Bouvardias as autumn- and winter-flowering plants, and especially when cut flowers are much in demand, they are not so generally nor so extensively grown as their merits deserve. Even in many places where they are grown, they are not cared for so well as they might be: indeed, one seldom sees what may be called a well-grown plant, the general run of them being long and leggy, with a tuft of leaves, and perhaps a small half-developed truss of flowers, at the top. Now, considering how easy the cultivation of these plants is, with a very small modicum of care they may be grown so that they will be an ornament to the greenhouse instead of being the reverse, and they will then amply repay the cultivator for the little extra care bestowed on them.
When there are a few old plants, they should be pruned back much in the way we do Fuchsias, and put into heat early in February, to get cuttings from. A vinery at work suits them well. When the young shoots are long enough to make cuttings - that is, when they have made three or four pairs of leaves - they may be taken off, and struck in the usual way, say in 6-inch pots. The pots should be filled with crocks to one third of their depth, and then a layer of ordinary soil, merely to form a bed for the silver-sand, which should be about one inch in depth. Insert the cuttings, press them pretty firmly into the sand, water through a fine-rosed pot, and plunge the pots up to the rim in a hotbed or other place where a brisk bottom-heat is maintained. They must be shaded from bright sun, and get an occasional dewing from a syringe in the evenings of hot days. They will have formed roots in about three weeks, when they may be potted off either singly in small pots or three plants in a 4-inch pot, using good fibry loam and leaf-mould in equal proportions, and a fourth part of silver or river sand. They should then be returned to the hotbed, or put into a warm pit, and kept rather close, and shaded for a few days, until they begin to root into the fresh soil.
The temperature may range about 60° at night, with a corresponding rise by day. A slight dewing from the syringe on the evenings of bright days will very much refresh them. In the course of a few weeks they will want a shift into larger pots, - those in the small pots into 4-inch, and those in the 4-inch into 6-inch. They do not care for large shifts. A little peat-soil mixed with the other is an advantage to them, but not absolutely essential. They should be kept well pinched while young, so as to make nice bushy plants. In potting, the soil should be pressed firmly about them, as they are fine-rooting plants, and do not like a loose damp soil. In large pots especially, care is required in watering not to give it oftener than needed, and then in sufficient quantity to wet the whole soil in the pot.
They should be kept in a warm house until about the beginning of June, when, being previously hardened off, they may be turned out into cold frames or pits, and set on a bed of ashes; or still better, plunge the pots in the ashes, which will save such frequent waterings. Let them have plenty of light and air, and still attend to the pinching. A few of them may be introduced to a warm greenhouse about the beginning of October, when they will very soon come into flower: others may be introduced at intervals as required, but all of them should be housed before any danger from frost is anticipated.
Where pits or frames are not readily available, they will do nicely planted out in a moderately rich and sheltered border. In this case, however, they need not be shifted into larger than 4-inch pots at first, and not planted out before the middle of June, having been previously well hardened-off. Still attend to pinching and watering, if necessary. In the beginning of September they may be lifted carefully, and potted up either singly or in groups, as required. When potted, water them well, and set them in a cold frame, which must be kept close and shaded for a while, until they begin to root afresh, when shading may be dispensed with, and air given - moderately at first, and afterwards more liberally, until by-and-by the lights may be removed altogether through the day, replacing them at night. The after-treatment will be the same as described above. A successional batch of cuttings should be struck during the month of May, only these should be kept in pots and grown in cold frames or pits. These will come into bloom later in spring, and will be very useful, before forced flowers come in. Of course, the time of blooming will be regulated by the amount of pinching they receive.
There are a good many varieties of Bouvardia, but we think the most generally useful are Vreelandii, elegans, Hum-boldtii, and corymbiflora. J. G. W.