If an imported Orchid such as a Cattleya or Lælia, which has been cultivated under glass for several years and has many pseudo-bulbs, be turned out of the pot and the roots freed from the potting material, it will be seen that the new roots which nourish the plant are confined to the freshest pseudo-bulbs, and that the roots beneath the older pseudo-bulbs are in such a condition that they are useless in the economy of the plant. This fact goes to show that the old pseudo-bulbs are being supported by the newer growths, and, that they are seriously impeding the full development of the flower-producing part of the specimen. In such cases it is a common thing to see large specimens collapse and die off, the decay being traceable to the old bulbs in the centre of the plant. It is, therefore, better to remove old pseudo-bulbs behind the last three or four leading ones, and, if it is desired to retain all leading portions of a large mass in one pot or pan to form a specimen, they should be potted together, when it will be found that, given reasonable treatment, they will make better specimens than if left in a mass. In the case of varieties that need to be propagated, the pieces removed should be placed in comparatively small Orchid pans or baskets, properly labelled, and in due time useful and often valuable specimens may be secured from material which would only have been detrimental to the parent plant. The same kind of treatment will be found equally beneficial in the case of garden hybrids which have been cultivated long enough to have a number of back bulbs. In such cases the plants frequently degenerate after the first two or three years, until they produce inferior flowers, but the removal of the back pseudo-bulbs results in giving the flowering growths the full benefit of the root action, and consequently the plants again produce flowers of good quality.
Potting time is a very convenient season to give special attention to the removal of useless leaves and pseudo-bulbs, as the plants can be readily handled when they are out of the pots.
All useless parts removed should be taken out of the house and burnt. It is a common practice to throw the leaves under the stage. No rubbish of this, or any other kind, should be allowed in the Orchid house, as it forms a harbour for insects and is, in other respects, objectionable.
CHAPTER VII
PROPAGATION BY DIVISION
It used to be thought a very delicate operation to divide an Orchid, or to remove any portion of it for the purpose of obtaining another specimen, and, when the operation was carried out, it was thought to be at the risk of the plant and its offset.
In the case of badly grown plants, or where the houses are unsuitable for growing Orchids successfully, there may still be considerable risk in the process; but under ordinary conditions, and where the plants have proper accommodation, there is no risk whatever; it may be said that plants are never in better health than when they are divided at reasonable intervals. If we consider the case of Cypripedium insigne Sanderæ, some of the white Cattleyas, and many other Orchids which were imported only as single specimens originally but which are now well represented in gardens, the advantage of dividing the plants is readily seen.
Pseudo-bulbous Orchids with progressive rhizomes, such as Cattleyas, Lælias, Oncidiums, and Odontoglossums, should be divided by severing the rhizomes, retaining two or more pseudo-bulbs together. This operation can be done at any season of the year, but it is most convenient to do it at potting time, and, for preference, just before the commencement of the natural growing season of the plant. Small pieces should be placed in small Orchid pans or baskets, but larger ones may be potted at once and placed on the stage with the other plants.
Dendrobiums may also be propagated by dividing the plants, but a large section of the genus may also be propagated by cuttings of the pseudo-bulbs. This method is specially useful for increasing a rare and fine variety of Dendrobium nobile or others of the section, as a good supply of plants can quickly be obtained in this way. The method is to cut the pseudo-bulbs into lengths of two or three inches and to place them in small Orchid pans, six or eight in a pan, suspending the pan in a warm, moist, house. The Thunia section of Phaius, Epidendrum radicans, and some other Epidendrums and Orchids of similar growth may be multiplied in this manner. Further remarks on propagation will be found under the names of the genera enumerated.