Volume Number: 1  2  3  4  5  6  7  8  9  10  11  12 

 

MAKING THE GLADIOLUS SURPASS ITSELF

TEACHING THE PLANT NEW HABITS

The history of the growth of ideas shows some curious paradoxes. As a minor illustration in point, it may be recalled that an English clergyman was doing his best-and a very good best it was-to build up evidence of the mutability of natural species at a time when it was rankest heresy to suggest that species are mutable. The clergyman in question was the Honorable and Reverend Dr. William Herbert, Dean of Manchester. His work was carried out in the early decades of the nineteenth century. He was a horticulturist of great skill, and he labored assiduously with many plants. And among those with which he attained conspicuous and striking results that seemed to belie the botanical beliefs of the period, was the plant now familiar in every garden as the Gladiolus. The time when the important work of this clerical amateur was carried out was one in which such men as Erasmus Darwin, the poet Goethe, and the French biologist Lamarck were advocating the idea of the mutability of species. And no doubt the Rev. Herbert had some of their theories in mind as he went about his plant experiments in the gardens of the Manchester Deanery. Yet in the main he was probably quite unconscious of the full significance of the experiments that he was performing. The particular experiments that are of interest to us in the present connection are those in which he hybridized one species of Gladiolus with another, and in so doing not only produced new races of gladiolus, but proved to his own satisfaction that these new races were altogether fertile. Almost half a century later Charles Darwin in his "Origin of Species" had occasion to quote the opinion of the Rev. Herbert, based on his experiences with this flower and several others, to the effect that hybrids are not necessarily sterile-a point that was still ardently in debate. He even cites Herbert as having claimed that the hybrids gained in fertility over the original species-a fact which Herbert himself regarded as being "a strange truth", but regarding which Darwin, writing with fuller knowledge, asserts that it was by no means so strange as it would appear. To be sure, nothing revolutionary came directly from the reverend horticulturist's experiments. He produced interesting new varieties of flowers, but the theoretical bearings of his work were doubtless quite ignored by his fellow clergymen, and, indeed, as I have already suggested, were probably only vaguely realized by himself. Yet as we look back on this work now, from the new point of vantage that Darwin gave us, we can see that the work of this amateur horticulturist must have had its share in disturbing the ideas of at least some of the persons to whose attention it came, and in preparing the way for the new view of the flexibility of species that now seems so much a matter of course that we can hardly realize how revolutionary it seemed to our forebears of two generations ago. A demonstration made with a plant that grows in everybody's garden, has force that comes home to us more cogently than records of any number of observations of animals and plants of tropical forests and South Sea archipelagoes. And a number of new species of plants, gladioli among others, that the Dean of Manchester created by hybridizing old ones made their way into the gardens of Europe, and gave their message, we may be sure, here and there to a receptive mind in substantiation of the disputed evolutionary doctrine, which, even before the publication of Darwin's "Origin of Species", was exciting the interest of the thoughtful.

OTHER GLADIOLUS HYBRIDS

Before the gladiolus made its full conquest of the popular gardens, however, it was further improved by other gardeners, both in England and in continental Europe. The species that the Rev. Herbert had crossed were the showy Gladiolus cardinalis and the smaller but more free-flowering Gladiolus blandus. Subsequently he crossed a number of other species, and produced races of great beauty and fertility. But a race produced by Mr. Colville at Chelsea in 1823, by fertilizing the form known as Gladiolus crislis with the pollen of Gladiolus cardinalis gained additional popularity. It was not until 1837, however, that the form was originated which was to make actual conquest of gardens throughout Europe, and presently to attain corresponding popularity even in America. This new form which became the parent from which most modern varieties of gladiolus have been developed was raised in 1839 by M. Bodinghaus, gardener to the duc d'Arenburg of Enghein. Like the other hybridizers, he used Gladiolus cardinalis for one parent form, the other parent being a species known as Gladiolus psittacinus. We have seen that the cardinalis was used by the earlier hybridizers. It appears that the psittacimus was also used in hybridizing experiments by the Dean of Manchester. But either he did not make the precise cross that was now made by the Belgian gardener, or the strains he used were somewhat variant; for the hybrid now produced had qualities that gave it a new appeal to flower lovers in general, and in particular made it a flower of such easy cultivation and such striking appearance as to make a strong bid for popularity among amateurs. It gained such vogue as to be thought of everywhere not only as a distinct species but as representing a type form of the race of gladioli. It was named Gandavensis, from Gand (Ghent), the place of its origin. It is believed, however, that the form of gladiolus that came to be known everywhere as the Gandavensis has in its racial strains the blood of many other species beside the original parents. It is almost certain, for example, that the strain of G. oppositiflorus accounts for the modifications of form and for the introduction of a tendency to produce white flowers; and that strains of G. blandus and G. ramosus have also been introduced. In a word, the form of gladiolus that came to be familiar everywhere under the name Gandavensis is not merely a hybrid, but a hybrid that probably carries the racial strains of at least four or five species, and possibly of a good many more than that. All of which is essential to an understanding of the later developments of the race of gladioli. For when we come to investigate the pedigrees of the chief races of gladiolus that are now found in our gardens, we learn that, practically without exception, they are hybrids that carry the Gandavensis strain among others, and hence are multiple hybrids, the precise lineage of which is too intricate for tracing. It is this fact that accounts for the wide range of variation as to form and color that characterizes the gladioli of our gardens. For the hybrid races have practically supplanted the original species everywhere. The same thing is of course largely true of most other cultivated flowers, and it is altogether true of the cultivated fruits and vegetables. As regards a large proportion of these, the cultivated varieties have not only supplanted the original species but no definite record remains of the original species themselves. The case of the gladiolus differs, and gains added interest, in that the original species were brought from Southern Africa to Europe only a little more than a century ago. The development of the new hybrid races under cultivation, and the elimination of the parent forms by their improved descendants, has taken place in so comparatively short a time that its chief steps are matter of record, as we have seen. So the story of the gladiolus has elements of educational interest for the plant developer that are quite lacking in many of the cultivated plants which attained relative perfection at an earlier period.

EARLY WORK AT SANTA ROSA

There are a few species of gladiolus that are native to Europe and Asia, but the ones that were chiefly used by the early hybridizers came from South Africa, as already related. Doubtless this fact was not without significance in determining the results of the work of the early cultivators. We have seen illustrated more than once the effect of transplanting a plant to new soils, and in particular of transporting it from one hemisphere to the other. We cannot doubt, then, that the change in the seasons and in the soils and climatic conditions in general had a share in promoting the variability of the gladiolus when brought to Europe, although, as we have seen, the tangible stimulus to variation was given through the now familiar method of hybridization. And, by the same token, we may suppose that when the gladiolus was finally brought to California, shifted thus half way 'round the globe from its new home in Europe, there was an added stimulus given, urging the plant to still further modifications of habit, and supplying yet other elements of variation with which the plant developer might work. At all events the gladioli in my gardens at Santa Rosa and Sebastopol have proved responsive and adaptable. And further modifications have been produced in the much modified flower that add greatly to the value of what was from the outset one of the most popular of ornamental plants. I began work with the gladiolus about the year 1882, starting with the Gandavensis hybrid, the origin of which has already been described. At that time there was no great interest taken in America in growing gladiolus seedlings, but I was able to secure a large number of the best types of Gandavensis, and also obtained bulbs of about a dozen of the natural species. I obtained my material not alone from American growers and the cultivators of Europe, but also directly from South Africa. I began from the outset to experiment on a comprehensive scale, raising the gladioli by the half acre and acre on my Sebastopol place. The first fault observed in the seedling gladiolus was that the blooms would not stand our California sunshine. Under the glare of the California sun, the blooms would wither in a single day, sometimes in a single hour. Other serious defects were that the stalks were too slender, and the flowers too far apart on the stalk. Moreover, the flowers were small, they were illy arranged on the stalks, giving an untidy appearance to the plants; and often they were only half open when at their best. The colors of many varieties, on the other hand, were fine, it being evident that selection had been made largely for color, by some at least of the earlier experimenters. My first object, then, was to remedy the defects just mentioned rather than to modify the color of the gladioli. In particular I sought, while improving the stalks and the arrangement of flowers on the stalks, to make the petals of the individual blossoms stand out flat and in regular sequence. The work progressed along the lines of hybridizing and selection with which the reader is already familiar. I hybridized freely, introducing strains of the long neglected natural species to give added virility and stimulate still further variation, thus providing materials for selection. Growing the plants by the acre, I had abundant material for choice, and my usual method of choosing only a few of the very best representatives of the different forms that seemed worth developing, destroying the rest, was rigidly exercised. I succeeded so well that in the course of a few years there developed varieties which were introduced with new names, and which made their way everywhere, and were highly prized by gardeners throughout the United States. Doubtless the most interesting development in this early period was the form named the California. This was a really magnificent semi-double variety which not only excelled in the form and size and color of the individual blossoms, but which had the added peculiarity of bearing the blossoms all around the stalk like a hyacinth, instead of merely on one side of the stalk as had been customary with all other varieties of gladiolus. Even at the present time, although the varieties of gladiolus have been subject to rapid development within the past few years, I recall the California as one of the most beautiful flowers of the family. Unfortunately this plant was lost, probably by freezing, along with the entire stock of other gladioli, by an eastern dealer to whom it was sold. My gladiolus colony progressed admirably, and the new forms attained a degree of virility that made it no more difficult to raise them than to raise potatoes; indeed, much less difficult, inasmuch as the gladiolus bulbs in California do not require to be dug or stored, but continue their growth throughout the year. The only object in digging them is to divide and separate them for multiplication. The forms of the plants, and the manner of bearing, as well as the shape and arrangement of the blossoms, improved year by year, and the new varieties of gladiolus came to be well-known to dealers throughout the country, and were still under process of development when an unexpected complication put an end, for the time being, to my further work with this plant.

WAR WITH THE GOPHER

The complication manifested itself in the discovery that entire rows of the gladiolus bulbs had been eaten by pocket-gophers, which had tunnelled their way into the grounds, and, boring beneath the gladiolus beds, had feasted on the bulbs, destroying large numbers of them (mostly during the dormant season) before I discovered the presence of the marauders. The plants do not wither at once even when the bulbs are greatly injured, or in the dormant season totally destroyed. So long rows were destroyed before I knew the necessity of combating the enemy. The attempts to exterminate the pests were at first so unsuccessful that I presently decided to give up the gladiolus colony altogether. I sold the entire lot to an amateur Canadian horticulturist, Mr. H. H. Groff, a banker, of Simcoe, Ontario, and for a good many years my experiments with the gladiolus were not renewed. Meantime, every effort was made to exterminate the pestiferous gophers, whose depredations were of course not confined to the gladiolus, and through which I suffered an annual loss of certainly not less than a thousand dollars year after year. Not alone with the gladiolus but with other bulbs it seemed that the animals took special delight in attacking the choicest plants. And the question of their destruction became finally a very urgent one. Numerous methods of combating the pests were tested. A double box trap set in gopher holes was cumbersome and not very effective. An awkward iron trap was supposed to catch the gopher when he poked his nose against the trigger, but missed fire or failed to score a hit oftener than otherwise. One form of trap after another was tried and given up. Attempts to smoke out the animals proved ineffective, as the gopher instantly builds a wall to shut out the smoke. Bisulphid of carbon, which gives off a poisonous, heavy gas, was tested with equal lack of success. About the only resource was the use of poison, commonly called strychnin, placed on a piece of apple, potato, or carrot, combined with the use of a wire trap, in the hope that if one failed the other might prove effective. But in spite of all these methods the gophers multiplied, mostly from neighboring fields, where their damage to ordinary farm crops was not so marked. A few years ago, however, a gopher gun was invented that practically solved the problem. This consists of a trap so arranged that when the gopher pokes his nose against the trigger a charge of powder explodes beneath the animal, killing him instantly by concussion. This device proved more effective than all others. Sometimes 35 or 40 gophers were destroyed in a day about the borders of my gardens. And in a short time the gophers were so nearly exterminated that they ceased to be a pest. When these old enemies of the bulbous plants were thus finally subjugated, after years of effort, I determined to take up again the cultivation of the gladiolus. In the meantime, the gladiolus had been much under cultivation elsewhere, and its general and special qualities had been greatly improved. But there remained plenty of modifications that could be made to advantage, and in starting a new series of experiments I had no difficulty in discovering faults to be remedied.

RECENT WORK WITH THE GLADIOLUS

One of the modifications, to which reference has already been made, had to do with the arrangement of the flowers on the stalk. My success in developing a race having the flowers arranged on all sides of the stalks has already been referred to. In taking up a new series of experiments, I attempted to improve on the earlier variety, by shortening the stems of the flowers, so that they were compelled to arrange themselves more compactly around the stem; by ensuring regularity of placement; and by diversifying the plant arrangement. Some forms were developed having two ranks of flowers, one on either side of the stem. Other races were developed with flowers in four ranks; yet others with the flowers in a spiral. Meantime the individual blossoms were enlarged in size, and their stems shortened, so that, when grown in a spiral about the stem, they crowd one another, making practically a solid mass of petals. The contrast in appearance of a stem of gladiolus flowers arranged on this new plant with the old form in which the blossoms grew only on one side of the stem, or at most on opposite sides, is very striking. Attention was given also to the modifications of the form of the individual flowers. In one form, petals were developed that are broad and ruffled so that they overlap, and thus give the appearance of a double flower. In another form the tendency of the anthers to turn to petals was accentuated through selection until a double variety was produced; and in one or two cases the extra petals were added without affecting the natural organs. In yet another form, and the one that I personally admire most, two flowers appear to be fused into one, so that twelve petals are presented instead of six. The variety was fixed so that the flowers on every stalk come in the same way, constituting a double flower of an unusual type. Particular attention was also paid to the development of regularity of petal in the case of the double gladiolus flowers. Irregularity of petals may be attractive in such flowers as the rose and the carnation, but with the gladiolus the double blossoms are less beautiful than the single ones, unless the petals are very regular. I experienced no great difficulty, however, in making the petals regular, as well as increasing their number by selection.

STUDIES IN COLOR

In the newer series of experiments, especial heed was given, also, to the matter of color variation, seeking for clear and brilliant colors of varying shades. The blending of shades, and the arrangement of lines, dots, and edges of different color on the petals were all carefully taken into account. There is opportunity for skill in the blending of different shades in a flower of such diversity of color as the gladiolus, akin to the painter's skill in mixing pigments. One learns that there are certain combinations that will produce disagreeable colors, whereas others will result in new shades of exceptional brilliancy. The characteristics of each flower to be worked into a hybridizing combination must be carefully studied. If, for example, we cross a yellow gladiolus with a white one, we are likely to get a dingy white that is by no means agreeable. The cross of a pale pink with a white form is likely to give us a still paler pink, which would not be regarded as an improvement. Again, from the blending of two nearly white strains, you may get dark colors in unpredictable combinations. By studying the combinations, however, and making rigid selection among the seedlings, it will be discovered that there are certain color tendencies that tend to be dominant, and that, as a rule, may be expected to repeat themselves in the hybrid offspring, overshadowing the less fixed colors. Still the races of gladioli are so blended, and the color factors in their germ plasm so mixed, that one may confidently expect to find new and interesting combinations among any large lot of hybrid seedlings. Indeed, it is not necessary to make new crosses in order to get interesting new types, since, as we have seen, all cultivated races of gladiolus are hybrids that carry many racial strains, and hence manifest the tendency to vary that we have seen everywhere manifested by hybrids in second and later generations; the pioneer work having already been accomplished with nearly all our cultivated fruits and berries, and most cultivated flowers. Nevertheless, it is of course possible to exert a directive influence through selecting parents for crossing, and further direction may be given by selection among the seedlings for any given color or combination of colors. So new races with unique color combinations may readily develop, and, even if these are not at once fixed, they can of course be propagated indefinitely by bulb multiplication. Here, as with other plants, all forms grown from the offshoots of a bulb will reproduce the qualities of the parent form, and a new race may thus be spread indefinitely. Notwithstanding the great diversity of colors of the different hybrid races of gladiolus, there have until recently been no gladioli that could accurately be described as pure white. Where so-called white varieties have appeared, they have a dinginess that suggests the presence of an underlying pigment; also there are spots, stripes, or featherings of other colors, especially on the lower petals. That the hereditary factors for pigmentation are really present in these so-called white flowers, is demonstrated by the fact, already noted, that in crossing two of these we may produce varieties that bear colored flowers. But the fact that these crosses of white gladioli produce flowers showing a great diversity of color, suggests obviously, the possibility of sorting out among these offspring, in the second generation, some that contain only the hereditary factors for whiteness. I have made this attempt, and by rigid selection have produced a race of white gladioli which, when further perfected, will constitute, I think, an interesting acquisition. Already these are partially fixed, and other growers of gladioli have observed the same fact. Already the white gladioli breed fairly true, and further selections, with reference to the perfection and fixation of the type, will give us a race of white gladioli that is sure to meet the approval of the public. But here as elsewhere there is danger that in selecting for one quality other qualities will be neglected, so that the flowers are not kept up to their best standard. Hitherto there has been no blue color in gladioli, any more than in the poppy, except, perhaps, submerged in combination with some of the darker colors. And for this reason, it has been found by all growers of the plants far more difficult to produce a blue flower than any other color, and until quite recently nothing approaching the really blue gladiolus had been produced. The first blue ones introduced were in reality more purple than blue. Nearly all hybrid varieties have shown lines of bluishness or smoky blue at times. The first gladiolus that could really be called blue was the one sent out from Europe under the name of Hulot. This had a small flower, and in other respects resembled the older gladioli-a dark purplish blue in color. By crossing this with white varieties of large size, pale blue with extra large fine flowers were produced by me. Two years ago, one appeared of very large size, and perfect in all respects with a true blue color. The crossing of the gladiolus presents no difficulties. It is merely necessary to cover the three-parted stigmas with pollen of the desired parent so thickly that bees and humming-birds cannot interfere with the experiment. In working on a large scale, it is convenient to place rows of different forms that one wishes to hybridize side by side, so that pollen may be readily transferred from one row to another, in walking along the rows, each forenoon when the stigmas are receptive. Also this arrangement allows the hybridizing to be carried out by the hummingbirds which are always aids in the fertilization of these tubular flowers. Here as in most other experiments, I have found that the results of the reciprocal cross are the same; it makes no difference which parent is the pollenate and which the pistillate member. So the seed from the contiguous rows of gladioli thus hybridized may be saved in a single lot. My experiments with a new strain of hybrid gladioli have now progressed so far as to assure the development of some greatly improved varieties. New crosses and rigid selection are giving larger flowers, brighter colors, more compact stalks, and a tendency to multiply more rapidly from the bulblets-and especially with greater freedom from disease. The propensity to revert toward the original type of the wild species-small flowers, long slender stalks, closed blooms, dull coloring, narrow leaves, and poor constitution-is being subordinated as the selection is carried through successive generations. And while there will be no metamorphosis in the essential characteristics of this beautiful and popular flower, further modifications of detail that are of no small practical significance may confidently be expected.

-We may well suppose that when the Gladiolus was finally brought to California, having been shipped first from South Africa to Europe and then from Europe half way around the globe, there was an added stimulus, urging the plant to still further modifications of habit, and supplying yet other elements of variation, such as form the basis of all plant development work.

This text is from: Luther Burbank: his methods and discoveries and their practical application. Volume 9 Chapter 6