CHAPTER XIX. Hybridising and Raising Seedling Orchids

HYBRIDISING AND RAISING SEEDLING ORCHIDS

A new interest has been added to Orchid culture by the pursuit of hybridising and raising seedling Orchids, which commenced with Calanthe Dominyi, raised in the nurseries of Messrs. Veitch and recorded in the Gardeners' Chronicle in 1858. The practice has now become general, and a large number of Orchidists arrange for the production of new Orchids from seeds, while even in small collections some attention is given to the matter. When the engrossing pursuit is first taken up, the operator should neglect no opportunity to make himself conversant with the structure of the flowers. This may be done effectually by carefully examining any available flowers, and by making longitudinal sections of the bloom by cutting them in two, commencing at the apex of the column and finishing at the ovary and pedicel. This operation exposes the various organs that are concerned in the fertilisation of the flower.

In most Orchids, such for instance as Laelias and Cattleyas, it will be seen that the pollen masses are situated at the apex of the column covered by the anther cap, the stigma being in a cavity in the face of the column beneath it.

In Cypripedium there are two developed anthers; the viscous pollen masses are not enclosed in cases, but are placed opposite each other; the stigma is a shield-shaped body seen inside the lip on the under side of the column, and the stigmatic surface is not viscous.

The details of the structure of the flowers being fully understood, it will readily be seen that the first process in the production of seeds is to fertilise the flower intended to bear the seed capsule with the pollen of the other parent selected. This is readily accomplished by lifting the pollen masses beneath the anther-cap with a thin pencil or sharpened stick and placing them on the stigmatic surface of the seed-bearing parent.

Flowers which are intended to be fertilised for seed-bearing should have their own pollen carefully removed before the pollen taken from the other plant is introduced, the pollen removed being used to effect the reverse cross, or to fertilise another species if desired.

In fertilising small flowers with the pollen of larger species, as in the case of Sophronitis grandiflora with the pollinia of the larger species, the pollen masses may be cut and a portion of it used in crossing the smaller flower. When the flower of a plant has been fertilised, the plant should receive special attention; if it is a Cattleya, Laelia, or one of the large-growing epiphytes, it should, after the pseudo-bulb bearing the flower has had a number attached to it corresponding to the number in the stock-book in which the crosses are recorded, be suspended from the roof in a comfortable and not draughty situation. If the plant is in a pot, the pot should be placed in a basket and suspended; or if a suitable position can be found on the stage, it could be placed on an inverted pot to bring it into prominence and secure for it careful attention. Where there is a number of seed-bearing plants, they should be arranged together in the respective houses in which they are grown.

Early in its development, the seed capsule should be supported by ties, which, however, should not bring it into an unnatural position, or press tightly on the part supported. From this time failure may arise from the conflicting natures of the agents used, or from various causes. Even the production of a fine and seemingly mature fruit is not a certain indication of good seeds, for seed capsules have been produced by irritation of the stigmatic surface by grit or dust, but no fertile seeds can be thus produced. On approaching maturity, a tie should be made round the middle of the capsule to prevent loss of seed when the splitting of the capsule takes place, and, when it is thoroughly mature, it should be removed, placed in a flower-pot lined with tissue-paper, and put on a shelf in a dry potting-shed until so thoroughly ripe that the seeds are being shed in the tissue-paper covering.

At this stage it is possible for the first time to determine whether the seed, or any of it, is good or not. Examination with a strong lens will show whether the minute seeds are good or not by the presence or absence of the embryo in the centre of the elongated covering, which in imperfectly developed specimens is chaff-like and not thickened in the middle as are good seeds. Where no good seeds are found, it is the custom of some growers to discard it at once, and where but few good seeds appear, attempts are made to discard the chaff and to retain the supposed good ones for sowing. Where space admits, however, especially with the beginner, it would be more prudent to sow a portion of the contents of the capsule, whether supposed to be good or not.

SEED SOWING

A number of the seeds of all seed capsules should be sown as soon as they are ready, the remainder being carefully stored for sowing later if required, the seeds sown and those retained being carefully marked with the number in the record book.

The manner of sowing the seeds varies in different establishments, satisfactory results having been obtained under very dissimilar conditions. Failure at first is the usual record of the amateur taking up Orchid hybridisation, although some few get fairly good success from the commencement, while those who have had a run of bad luck usually conquer in the end if they persevere. A scientific reason for some failures has been given, namely, that an endophytic fungus said to be necessary to the development of the freshly germinated seeds is wanting in the early stages, but may be developed naturally after a time, and a better state of growth result. Be that as it may, it is a curious fact that the line of demarcation between failure and success in the matter of raising seedling Orchids is very narrow, and, when the operator succeeds in raising a fair proportion of the seeds sown, he is generally surprised at his former want of success, apparently under practically similar conditions. Formerly the common practice was to sow the seeds on the surface of the material in which the parent plant was growing, or a plant of some kindred variety. This practice has been generally satisfactory and continues in most amateur collections to the present day. A plant in a basket, or suspended pan or pot, is best, the subject being chosen for the good quality of the peat, Osmunda fibre, or whatever material the plant may be growing in. The Sphagnum-moss on the surface should be clipped very short, the plant thoroughly watered with rain water, and allowed to drain for a few hours. The seeds should be sown a few at a time, on the point of a knife or thin strip of hard wood or ivory, and carefully and evenly distributed over the surface of the material in which the selected plant is growing. In all cases the number of the record in the stock-book should be attached, a small celluloid tablet fastened by a thin wire being the best label, as it is clean and durable. Hybrids of Laelia, Cattleya, and other true epiphytes should be suspended in a warm, intermediate house, and Cypripediums and terrestrial Orchids may be sown in a similar manner in the pots of either the seed-bearing subject or similar kinds and placed in a moist, sheltered corner of a house, in which a genial warmth is maintained, the plants being elevated on inverted flower-pots. Once the seeds are sown, the plants fostering them should never be allowed to get dry.

Odontoglossum seeds come up best when sown on the surface of established plants in the manner described. To ensure the best results two or three sowings of each should be made, and the plants bearing the freshly sown seeds placed in different parts of the house, some being suspended and others placed on the stage.

The maintenance of a continual and even amount of moisture after sowing, and until the seedling plants send forth roots, is of the highest importance. To water either with a spouted or a rose pot overhead would wash the seeds away. To avoid this, some resort to the practice of dipping the plants on which the seeds are sown, allowing the water to reach only to within an inch of the surface of the compost. This is better than watering overhead. Spraying with rain-water is an excellent means of securing uniform moisture, although it requires more care and attention than dipping. The sprayer is a great help in all stages of seedling Orchid growth, not only as a means of conveying moisture direct, but by spraying around the plants and on the staging it is a great aid to maintaining a moist atmosphere. Let the moisture be conveyed in whatever manner it may, it must not be forgotten that the seeds will perish soon after germination if allowed to get quite dry, either from failure of moisture in the material on which they are sown, or from an excessively dry air surrounding them. Against the above-mentioned practice of sowing the seeds on established plants, it is urged that in that way there is no certain means of keeping the different crosses from being mixed, by reason of the seeds of one kind getting into the water-tank and being thus conveyed and mixed with others; and by seeds falling from plants suspended overhead and coming up on plants beneath, and in other unexpected places. Such acquisitions, though often very acceptable, are puzzling, as there is no record of their origin, or if they come up amongst seeds which have a record, the chance introductions sometimes have a wrong parentage assigned to them.

CYMBIDIUM LOWIO-EBURNEUM

(This plant has been commended for its culture on two separate occasions by the R.H.S.)]

To lessen such risks, it is the custom of some growers to arrange a seed-raising case, constructed like an ordinary propagating case, in form like a miniature lean-to, or span-roofed Orchid house. This is arranged over a part of the staging where there is a slight warmth from the hot-water pipes. The staging has a few inches of cocoa-nut fibre, or chopped Osmunda fibre, fine ballast, or other moisture-holding substance, and on this a number of inverted flower-pots are closely arranged to form stands for the pots or pans in which the material for sowing the seeds on is placed: or a light, open wood-work staging is arranged. The favourite surface for sowing the seeds on is prepared by stretching a small square of coarse calico or fine light muslin shading material over a ball of Sphagnum-moss, and pressing it into a 60 or small 48 size flower-pot, so that the unwrinkled convex surface of the ball has the centre just below the level of the rim of the pots, the sides being lower. These are thoroughly soaked and allowed to drain before sowing the seeds on them, and they are then placed on the inverted pots in the case. The covering of the case is sometimes of the nature of hinged sashes to lift from the front, but the most convenient and best covering is that formed of sheets or panes of glass cut about one foot wide and of a length sufficient to cover the frame, by resting one end on a groove in the front side of the case, and the other on the top bar. A sufficient number of these sheets of glass should be provided to cover the frame; they are excellent, as they give a certain means of continual ventilation in some degree through the laps of the glass, even when closed, and they may be closely or openly arranged to regulate the amount of air admitted. Such pieces of glass can easily be removed to inspect the seedlings.

What is commonly called "coddling" causes great mortality among Orchids, and in this particular the use of seedling cases, if not very carefully and sensibly worked is less likely to be satisfactory than sowing the seeds on plants growing in the houses. Too much heat is very harmful. Odontoglossums proved difficult to raise at first, and this was mainly because the seedlings were kept too warm and close. If the cultures are carried on in the Odontoglossum house, success is generally attained, although the products are seldom so numerous as in Cattleya, Laelia, and Cypripedium hybrids.

Another plan adopted by some growers, and with tolerable success, is to place squares of Osmunda fibre in pans, and after soaking them, sow the seed on them. Others have discs of soft wood, such as Willow, cut across the grain and placed in flower-pots or pans with the fibre of the wood-grain uppermost; after soaking the discs, the seeds are sown on them. When not raised in glass cases, round or square pieces of glass are placed on the pots. Indeed, there is ample evidence that, provided good seeds are sown and placed in a suitable temperature, Orchid seeds germinate readily. The first sign of vitality is given by the good seeds assuming a green appearance; in time they become little spherical green bodies, which later produce a growing point; in due course the true root appears, and the little plants are ready for pricking off or transplanting into previously prepared store pots prepared with a good drainage of small crocks or broken charcoal in the bottom, some Osmunda fibre or other Orchid potting material, and an inch or so of very fine compost formed of decayed leaves, Osmunda fibre, or good Orchid peat and Sphagnum-moss in equal parts, the whole rubbed together through a fine sieve. Some add a proportion of sand to this compost. The whole should be thoroughly well watered before the tiny seedlings are placed a quarter of an inch or so apart in small holes in the surface of the compost and sprayed to settle them in position. Up to this stage the greatest mortality is observed. Wide crosses between species of dissimilar nature, and which have up to the production of the growth point or root appeared to be doing well, having shown that they did not belong to the unfertile, suddenly collapse. Those which have taken a long time to germinate have fallen victims to the minute fungi, and other low forms of vegetable organism, which, commencing at one or two spots, have gradually overgrown the surface of the pot and destroyed them. The stronger are often destroyed by small insects, while drip, however carefully guarded against, claims its share of the spoil. These things are specially vexing to the amateur who is working in a small way. To the expert cultivator who has a multitude of subjects in hand, and whose methods and appliances mitigate the evils, the losses are not so serious, for when Orchid seeds germinate freely they provide for losses when sown on a large scale. Nothing is gained by removing the little seedlings from the seed pot or basket too early. If thriving, they should be left until they are large enough to be handled safely. But where there is overcrowding, or "damping off," or decay from fungus, it is best to remove some or all of the little seedlings in any stage of growth to the store-pots.

The store-pots should be returned to the seedling case, or placed on a shelf near the glass in a warm, moist house, where the seedlings should increase in size until they are ready to remove to fresh store-pots, when they may be given more room; or if large enough, they may be placed singly in thimble pots, or three or four seedlings may be placed round the rims of thumb pots.

Seedling Odontoglossums, when large enough to occupy thimble pots, are found to thrive well when the pots are fixed in pans or shallow seed-boxes in Sphagnum-moss, and placed on a shelf near the glass in the Odontoglossum house, where, like other seedling Orchids, they should be lightly sprayed several times each day in fine, warm weather, and as often as may be deemed necessary in colder and dull weather.

From the time the little plants are established in small pots until their flowering stage, it is only a matter of ordinary culture, although, as a rule, the small seedlings are safer with four or five degrees more heat than is afforded the established plants. In the matter of growth from the seedling stage to the flowering plant, there is but little need of a resting season, even with species such as are deciduous when mature, although a diminished supply of water may be given for a short time to any which, having completed a growth, show no sign of developing a fresh one. In most cases, a thorough drying, even if it does not destroy a seedling, causes the flowering season to be delayed by a year, or even longer.

The careful shading of the seedling house is a very important matter. Very young plants do best in a subdued light, and until they are quite strong plants they should not be exposed to direct sunlight. A hot summer often kills even the plants which have been brought satisfactorily through a long winter. It is, therefore, advisable to have on the seedling house, in addition to the lath roller blind, running on supports carrying it well above the glass of the roof, either a second lath roller blind running an inch or so above the glass and beneath the upper one, or a permanent thin cotton shading, which may be tacked on in spring and left until autumn; or, preferably, so fitted that it can be rolled up when it is not required.

SELECTION OF SUBJECTS FOR HYBRIDISING

The best varieties procurable should always be selected for hybridising, it having been proved that crosses originally made with indifferent varieties are much finer when raised again from more carefully selected varieties.

There seems to be no certain limit to the possibility of crossing; even the most dissimilar genera may be crossed with some probability of getting a successful result.

POTTING MATERIAL FOR HYBRID ORCHIDS

From the time the little plants are well established in single pots, the same potting material used for all of their kind may be employed, the plants in the earlier stage having the potting material in a finer condition than that provided for the larger plants as they approach the flowering stage.

As with other important operations, in Orchid potting and in the material used the practice varies considerably, even in the best collections, and this points to the fact that if the accommodation is good, the houses properly heated, and other details of culture carefully carried out, the exact composition of the potting material is of minor importance. For Cattleya and Laelia hybrids and a large number of epiphytes grown with them the compost is made by tearing up the materials with the hand, or in some other way which will not break the fibres very much. Osmunda fibre forms one-half to two-thirds of the compost, the other third being made up of good Sphagnum-moss and Oak leaves or other decayed, dryish leaves. We do not recommend leaf-soil or leaf-mould, which was formerly strongly advocated, especially by Continental growers, who used it with disastrous results. The most that is done now is to mix a proportion of it with other potting material for Lycastes, Calanthes, Phaius, and similar strong-growing terrestrial Orchids.

For mixing with the compost for hybrid Orchids, some use crushed crocks, sand, charcoal, and a small proportion of each or either may be employed safely, although there is no real need for such materials.

Polypodium fibre may also be substituted for Osmunda fibre, or a proportion of each may be used. Orchid peat fibre, which used to be the chief potting material for Orchids, is still perhaps as good as any of the other fibres, provided a really good quality can be obtained, a matter which has become increasingly difficult.

For Cypripediums, and especially Selenipediums, a proportion of good, fibrous loam should be added to the compost recommended for epiphytal Orchids, the proportion of loam being increased as the plants get larger. Phaius, Calanthes, Zygopetalums, Zygocolax, and other plants of a similar character should also have a proportion of loam-fibre in the compost, and in these cases Orchid peat may be substituted for Osmunda fibre, if it is of good quality. So far as it has been tested, Osmunda fibre has an advantage over other fibres, in that it is more durable, retaining its fibre intact longer than any other. Osmunda fibre and Polypodium fibre in equal proportions, with an addition of leaves and Sphagnum-moss, make an excellent material for all young, epiphytal Orchids, the finer Polypodium fibre, if well worked in, giving substance to the more open Osmunda fibre.

For very small plants it is well to rub the mixture through a coarse sieve, but after the early stages the use of the sieve should be discontinued, and the compost carefully mixed with the hands.