Orchids Part 4

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 Phalaenopsis, Aerides, 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 Aerides 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.

Plants are also benefited greatly by having their position in the houses changed, and that is one of the great advantages of the periodical inspection, for during this process the relative positions of the plants are altered.

It should be said that Cattleyas and other common Orchids badly affected by disease had better be burnt, for it is cheaper to buy a healthy young plant than to waste time in trying to bring the unsightly and diseased specimens back to health.

The Cattleya Fly (_Isosoma orchidearum_), first imported probably with _Cattleya Dowiana_, and frequently with other Cattleyas since, affects the new growths, the grubs causing them to swell and rendering the growth useless. The same species, or one closely allied, also attacks the young roots of Cattleyas, Laelias, and their hybrids, causing unsightly galls on the points of the roots. Fumigation, with some safe preparation to destroy the fly, should be carried out, and every young growth and root-point as soon as they are seen to be affected should be cut off and burnt. By adopting these remedies it is possible to get rid of the pest. In purchasing freshly imported plants, care should be taken to reject those which show signs of having been affected by the fly.

Thrips, Red Spider, and Aphides occasionally appear in every collection, and the remedy is fumigation and sponging with an insecticide, which some growers prepare for themselves, either by pouring boiling water over coa.r.s.e tobacco tied up in a cloth and adding a little soft soap, or by making an infusion of qua.s.sia chips. But excellent insecticides can be purchased already prepared, which are guaranteed to be safe and effective, and being of uniform strength, they may be used with confidence if the instructions given with the preparations are observed strictly.

Avoid using paraffin and emulsions of paraffin, for it is dangerous, not only to the plants sponged with it, but to all the plants in the house, for it affects the atmosphere.

SCALE INSECTS

These appear much less in collections now than formerly, because the old large specimens are replaced by young and vigorous plants. Thirty or forty years ago, it was a usual thing to spend several days every year sc.r.a.ping the brown scales from tall plants of _Aerides odoratum_, _Vanda tricolor_, and other specimen Orchids, and what was called "cleaning"

was going on all the year round. Now there is much less need of such work, although scale will appear in its various species on one section of plants or another. In the periodical inspections, all plants attacked by it should have the insects removed by a piece of stick blunted at the edge and point, sponging the leaves afterwards with some diluted insecticide. Syringing with an insecticide, or dipping the plants in the liquid, should be avoided, for the quant.i.ty applied is likely to saturate the material in which the plants are potted and to run into the centres of the young growths and cause injury. By means of a sponge, it may be applied lightly or heavily, but the operator has command in each case over what he is doing.

MEALY BUG

Fortunately this pest is rare in Orchid houses, but when it appears it is easily destroyed in the same manner as scale.

c.o.c.kROACHES

The first of these insects to be noticed should be the signal for the laying of poison. Search should be made for the breeding quarters, which are often in the stoke-hole, or in some hot, dry corner of the house.

Various preparations are recommended, but the best still seems to be the old phosphor paste, which should be placed on pieces of paper in the haunts of the insects in the evening, and removed the next morning, a fresh supply being put down every two or three days so long as one of the insects remains.

SLUGS, SNAILS, AND WOODLICE

To combat these is more a question of diligence than anything else. The old remedies to attract them, such as lettuce leaves, or hollowed halves of potatoes, are still effective, and a walk round the houses with a light at night never goes unrewarded.

CHAPTER XIII

PERIODICAL INSPECTION

Whenever the time is to be spared, it is a good plan to overhaul one or other of the sections of Orchids thoroughly, and to have a more general inspection as soon as possible after the winter has pa.s.sed, and at the end of the summer, this latter inspection being the more important.

Cleanliness in everything around Orchids is one of the most important aids to successful culture, and, during the periodical inspections, plants which are not clean should be cleansed, their pots where it is required washed, and the staging and any part of the house requiring it thoroughly cleansed before the plants are rearranged. During the course of the work certain plants which would be benefited by being repotted, or divided, will be found, and these should be given attention. The water in the tub in which the green deposit on the pots has been removed by scrubbing, and as much of the other water used in cleansing as can be dealt with, should be poured down a drain outside the Orchid house. If thrown on the floor of the house, it leaves an unpleasant odour, which is harmful and lasts a long time.

During the inspection at the end of the summer the staging should be repaired where necessary, the heating apparatus carefully overhauled and defects made good, in order to minimise the risk of having to do the work during the cold weather. Where it is deemed advisable to black the hot-water piping, use only lamp-black and oil. Paint gives off injurious gases for a considerable time, and where persons have been incautious enough to use gas-tar the most lamentable results have followed, the mischief lasting for years. These periodical inspections and rearrangement of the plants are also useful in preventing the same plants occupying the same positions for too long a time. A change of position in the house is beneficial, even where the plants are not crowded; but in collections where the plants are closely arranged, to change their positions frequently, goes far to mitigate the evil arising from want of s.p.a.ce. In preparing for a thorough inspection of the plants in a house, it is desirable to remove a number of the plants to another house to make room to examine the rest without risk of breakage, the plants removed at the commencement being returned to fill the s.p.a.ce remaining after the work has been completed.

The Orchid grower is always supposed to have the plants under his direct inspection and to treat them with individual care, but these occasional reviews often reveal defects in some of the specimens which would otherwise have escaped for some considerable time.

CHAPTER XIV

ORCHIDS FOR THE CONSERVATORY

There are many dwelling-houses of moderate pretensions, especially in towns and suburban districts, in which the sole accommodation for plant-growing consists of the conservatory adjoining the house, and this is, in most cases, heated by one or other of the simple means at command for the purpose. The contents of such structures are usually unsatisfactory, the Pelargoniums, Fuchsias, and other soft-wooded plants which are arranged with some of the hardier Palms and Ferns being drawn into spindly growth, which results in a miserable supply of flowers for a short season, and afterwards in decaying foliage, which is not ornamental. Quite a new interest would open up to the owners of such places were they to turn their attention to acquiring from time to time a few of the Orchids which are now to be procured as cheaply as the less suitable plants, such as Pelargoniums. Already some successes have been recorded in this direction.

Let us consider the different cla.s.ses of conservatories, and the species most likely to succeed in them.

To take first the commonest kind of small conservatory attached to villa gardens. These are unheated structures except in the winter months, when the temperature cannot be kept from getting below 45 Fahr. without the aid of one of the oil-stove heating apparatus, or heat turned on from the pipe connected with the kitchen range, where arrangements for doing so have been provided. These means of applying artificial heat should be used as little as possible, and only to prevent the temperature falling below 45 Fahr., for in confined s.p.a.ces and with such means of heating, the atmosphere is better for the plants without the use of artificial heat, whenever the house can be kept from getting too cold without it.

In such conservatories, many of the Odontoglossums, Masdevallias, _Oncidium varicosum_, _O. crispum_, _O. praetextum_, _O. Gardneri_, the pretty scarlet _Sophronitis grandiflora_, _Epidendrum vitellinum_, _Lycaste Skinneri_, _Cypripedium insigne_, _Disa grandiflora_, and a number of other pretty and inexpensive species can be grown satisfactorily, especially if the Oncidiums, Sophronitis, _Odontoglossum Rossii majus_, and other of the smaller species be placed in baskets for suspending, a means of cultivation which suits them best, and adds to their decorative effect.

The next step is the larger conservatory adjoining many town and suburban dwellings. These are heated by a small boiler with hot-water pipes, a means, it should be said, which is the only satisfactory method of heating gla.s.s structures. To the species indicated for the smaller and less safely heated structures may be added a very wide range of subjects of great beauty. In such a structure the Palms supplying decorative foliage may be much restricted, or entirely dispensed with, as _Cymbidium Lowianum_, _C. giganteum_, _C. Tracyanum_, and any others of the section having evergreen leaves of much grace, are decorative plants at all seasons, and possess the further advantage of being furnished with fine spikes of flowers for several months in the year.

These large and strong-growing species are specially adapted for the conservatory, an Orchid house being unnecessary for them.

To the heated conservatory also may now be handed over the showier species and hybrids of the South American Cypripediums (Selenipediums), which, probably because of their very free-growing nature rendering them too large for the Orchid house, and the ready manner in which they may be increased, have caused them to be slighted lately by growers of collections of Orchids. The air of the conservatory, rather drier than that of the Orchid house, suits these plants admirably. Their bright evergreen foliage and tall sprays of white and rose, or greenish flowers tinged with purple, which often by succession keep the specimens in bloom for six months in the year, render them beautiful and interesting subjects for the conservatory.

The strongest and best kinds to be acquired are _Selenipedium longifolium_, _S. Sedenii_, _S. cardinale_, _S. calurum_, _S. grande_, _S. Schroderae_, and _S. albo-purpureum_.

_Cypriperium Charlesworthii_, _C. Spicerianum_, and _C. Leeanum_ should also be added. The larger, heated conservatories might well be furnished with the Orchids recommended rather than the plants generally used for decorating them, for these have to be changed frequently. The Orchids, if carefully tended, will grow permanently in the conservatory and be a source of never-failing interest. In these large conservatories, Stanhopeas in baskets for suspending are ornamental plants, and Sobralias on the floor or central bed would prove satisfactory. To those enumerated many more might be added, but in all cases it is best to get only evergreen kinds, which may be grown continuously in the same house.

CHAPTER XV

ORCHIDS AS CUT FLOWERS

Orchids having flowers with persistent perianths, in which the segments do not drop as in many other flowers, are of the highest value for cut flowers, as some or other of them can be obtained in every month in the year. Large quant.i.ties of the large-flowered Cattleyas, especially _C.

l.a.b.i.ata_, of _C. Harrisoniana_ and its near ally _C. Loddigesii_, _Odontoglossum crispum_, _O. Pescatorei_, Dendrobiums, and other showy Orchids are grown for cut flowers in nurseries where Orchids are not required for other than market purposes. In many private gardens, also, the same kinds of Orchids are grown for decorative purposes, even without a desire to grow a general collection. Those who arrange for a general collection of Orchids as their primary object often cut the flowers for their own use, or to give to their friends, and the following remarks may be useful to all cla.s.ses of growers.

A large proportion of the flowers of Orchids used for decorative purposes are in a great degree wasted by being cut in an immature state soon after the buds have expanded. Such flowers last but a very short time, and, if used for decoration by night, are only presentable for one evening. Orchid flowers should not be cut until they are fully mature and their tissues hardened. They last longer even if they are cut after they are past their best, than they do if cut too soon after expanding.

When mature, the flowers require less support from moisture pa.s.sing up the stem than most flowers, but if cut in an undeveloped state sufficient moisture cannot be obtained through the stems, even if well supplied with water, to continue the development, and the petals droop and the flowers soon wither.

[Ill.u.s.tration: PLATE V