CHAPTER XI
SPECIALLY RARE AND VALUABLE PLANTS
While every plant in the collection should be given the best possible care and attention, it is advisable to keep the more rare and valuable specimens immediately under the eye of the grower. It is often the case that albinos, rare varieties, and new species are allowed to get mixed up in the general collection, and a plant that could not be replaced may be hidden by the commoner things which are not of so much consequence. In the case of the best spotted varieties of Odontoglossum crispum, albino Cattleyas, and other exceptionally rare things, it is a good plan to arrange a batch of them together in the most suitable part of the house, or to place each on an inverted flower-pot at intervals along the staging, thus bringing them into prominence and facilitating the inspection of each at all times. Some use wire plant stands instead of inverted pots, but the moisture-holding flower-pots are preferable, if they are inspected occasionally to see that they are not harbouring insects. Albinos and fine varieties of Cattleyas and Lælias could be grown in suspended Orchid pans or baskets, to take them out of the general collection, and so grown they would make better progress than if placed on the stages. In the case of any plant not making satisfactory growth it is often beneficial to place it on an inverted pot to bring it more prominently under notice.
CHAPTER XII
DISEASES AND INSECT PESTS
There is very much in the old-time advice, "Grow your plants clean," for a very large proportion of Orchid diseases and insect pests are due to errors in cultivation, more especially in the regulation of the temperature and the ventilation. Insanitary houses lower the vitality of the plants, and vegetation, like human beings, is a prey to disease when kept in unhealthy conditions.
Spot, or Orchid disease, exhibits itself in various forms. It is caused, as scientists say, by different micro-organisms, but in effect it is practically the same whether in the form known as "Spot," often seen in Phalænopsis, Aërides, and Vandas, or in the decayed and blackened pseudo-bulbs of Cattleyas, especially C. Warscewiczii (gigas), which from an apparently healthy plant may develop a diseased condition of the pseudo-bulbs, and become useless in a few days. In all such diseases it will be seen that the tissues have collapsed, the result being brown or blackish spots on leaves or bulbs. Imperfect nutrition from lack of healthy roots is a frequent cause of this mischief, for Aërides and Vandas which have been affected with "Spot" recover in the new growth, for a time at least, if a satisfactory root action can be set up.
Propagation, by freeing the recently made parts of the plants from the old and worn-out back portions, which are not furnished with the roots necessary to support themselves is one of the best means of preventing Orchid diseases, and efforts should be made to keep the plants vigorous and, therefore, capable of resisting attacks by insect pests.