FOUR COMMON DOORYARD FLOWERS AND THEIR IMPROVEMENT
WORK ON THE VERBENA, THE PINK, THE PETUNIA, AND THE GERANIUM
My most interesting verbena was the one named the Mayflower. I use the past tense because I am not sure that any representative of the variety named Mayflower is now in existence. I have introduced the plant through a prominent horticulturist, but he apparently found it difficult to reproduce it with sufficient rapidity from cuttings and so attempted to propagate it more rapidly from seed. Unfortunately the verbenas are so mixed a tribe, and the various races so little fixed, that they do not breed true from the seed. And so when I myself sent to the horticulturist for a sample of the fragrant Mayflower verbena a few years later, I received a plant that had but a reminiscence of the distinguishing quality of the original. In the meantime, however, I had developed another race of fragrant verbenas, which was introduced in 1901 under the name of Elegance verbena. These are the two stocks from which a large number, at any rate, of the fragrant verbenas now under cultivation have been developed. My first fragrant verbena, the Mayflower, was developed after I had worked for many years with this flower and had grown great quantities of the seed for distribution. The plant from which the fragrant race was developed was found among many thousands, most of which, as is usual with the cultivated varieties, have a rather disagreeable odor. I had noticed, however, that there were members of the verbena colony that had a very slight fragrance, especially in the evening. So I began a careful search among them to find a plant the flowers of which had the most pronounced perfume. After a long search among the thousands, I found at last a plant that was distinctly fragrant, markedly surpassing in this regard any of its associates. This individual was of course carefully isolated and its seeds were gathered. In due course I had a number of seedlings among which some were found that produced flowers more fragrant than those of the parent. The selection was continued, according to my usual method, through successive generations, until at last a plant was found that is as fragrant as could be wished. The plant in question was an exceedingly large verbena-in fact one of the largest ever grown. The flowers it bore were of a rich rosy pink in color, the exact counterpart of the color of the familiar trailing arbutus or any flower of New England. Curiously enough the fragrance of the new verbena was also precisely that of the arbutus in quality, although it was much more intense, as was readily admitted by all who tested the two flowers side by side. It was for this reason that the new verbena was given the name of Mayflower. Several perfumers who saw this verbena were agreed that it would be of value for the production of a perfume. It was admitted by all that no verbena with a comparable odor had ever before been seen. The subsequent history of the Mayflower has already been told. It was purchased by a dealer, and although plants grown from cuttings made from it are probably in existence, I do not know where they are and do not know how to trace them. Aside from its fragrance, the Mayflower was an interesting type of verbena, owing to its size and prolific bearing and the beauty of its flower. But seedlings grown from the plant could not be depended upon to produce flowers that would reproduce the Mayflower odor. Indeed they could not be depended on to reproduce any particular characteristic of the parent plant. In point of fact, seedlings of the Mayflower produced plants bearing blossoms of almost every color-scarlet, crimson, almost pure white, yellow, deep cobalt blue, purplish. But not one of the many thousands I raised afterwards had the delightful flavor of the Mayflower.
THE MAYFLOWER ACCOUNTED FOR
As might be inferred from its variability, the fragrant verbena was a very mixed hybrid. It was the outcome of hybridizing experiments in which I had utilized the various races of the plant under cultivation. I had not only grown and crossed the ones that are in the seed catalogs, but also secured seeds from all four of the original species from which the cultivated verbenas have been developed, collected from wild plants in South America. It is quite unnecessary, however, to hybridize the verbenas in order to secure variation, as all of those that are under cultivation are themselves hybrids of very mixed strain, and the plant has been cultivated for a comparatively short period and none of the familiar forms breed true from the seed. The ancestors of the cultivated verbena were South American plants, and it is believed that there are four chief species that have been variously hybridized to produce all the forms now under cultivation. One of these bears flowers of brilliant red, two others have flowers that are rosy or purple in color, and the flowers of the fourth are pure white. The hybridized races show the breaking up of these colors, quite as might be expected, with the presentation of all the primary colors in many of their hues and gradations, although pure blues are not well represented, and pure yellow is very exceptional. But the point of greatest interest in the present connection is the fact that the white species of wild verbena, which is acknowledged to be one of the forms, whose strains have been blended with the others to produce the cultivated verbena, has what is described as a rich jessamine fragrance. The hybridizing experiments that ultimately gave us the perfected verbena were carried out less than a century ago, but in the meantime the strains have been so mixed and blended that it would be impossible for the most part to trace the characteristics of any given form of cultivated verbena with certainty. But it is obvious that the hybridizers and those who further developed the plant by selection were chiefly influenced by form and color, as has been the case with so many other flowers, and paid little attention to the question of fragrance. The verbena has been made to develop wonderfully symmetrical clusters, and its flowers have taken on the most gaudy hues. But in the main, as already pointed out, the odor even of the most beautiful specimens is disagreeable rather than attractive. Yet one of the wild parents, as we have just noted, was fragrant; and our previous studies of heredity give us full assurance that the factors for fragrance must be retained in some at least of the hybrid progeny, and will now and again make themselves manifest. That such is really the case, my fragrant verbena clearly enough demonstrates. To be sure its fragrance is not just that of the original. Some slight chemical modifications have taken place, doubtless through the blending of other chemicals that represent the odoriferous qualities of the other species, and it is only by rare exception that an individual appears having just the right combination to produce an attractive perfume. But the point of interest is that when such an individual does appear, as in the case of the Mayflower and the later form named the Elegance, the anomaly is accounted for quite adequately by a knowledge of the existence of fragrant species among the ancestors of the hybrid. Even if we had no knowledge of the existence of such an ancestor, we should still be justified in assuming that a fragrant verbena is really a case of atavism. It will be recalled that we invoked the existence of remote unknown fragrant ancestors in explanation of the appearance of our fragrant calla. But there is an element of added interest in the knowledge that in the case of the verbena the ancestor responsible for the quality of fragrance can be traced. It would constitute a very interesting experiment in heredity, should someone care to undertake to hybridize a fragrant verbena with an odorless one and to trace carefully the hereditary influence of this quality-noting, for example, whether it acts as a prepotent or as a recessive character, and whether it tends to reappear in the second generation in any fixed proportion of the progeny. It will probably be found that the condition that leads to the production of perfume of a particular type is so complex and itself dependent upon so many factors that it is not inherited in any simple and readily traceable relation. One of the distant relatives of the fragrant verbena is a fine shrub, worthy of introduction, known as the Alovsia citriodora. Another, as different as possible in appearance, is a little trailing plant known as Lippia repens. This little trailing plant is very valuable as a substitute for lawn grass. It requires less than one tenth the water required by blue grass, and only a fraction of the care. It need be sown only once or twice in a season, and throughout the summer it will cover the lawn with a dense foliage, and bear a mass of small blossoms resembling those of white clover and fully as attractive to the bees. Unfortunately the lippia is not very hardy, and when the temperature goes much below freezing it turns to a disagreeable brownish color. Thus it is not adapted to the cold climates of the Northern United States. If it could be given hardiness through selection and cultivation, it would prove a very important acquisition for the making of lawns that will withstand the summer drought. An allied species is the moss-like Verbena erimoides, which is an exceedingly pretty plant growing wild in the high Chilean mountains. In California it produces seed so abundantly and hence multiplies so rapidly that it becomes almost a weed. It is possible that new and interesting varieties of verbena may be produced by hybridizing the familiar cultivated ones with some of the wild species that have not hitherto been brought into the combination.
CARNATIONS, OR PINKS
It is rather anomalous that a plant should bear at the same time two popular names suggestive of colors so different as pink and carnation and the anomaly is not lessened by the fact that the plant itself bears flowers not only of the colors suggested but also of the purest white. Such, however, is the case with the plants that are known to the botanist as constituting the genus Dianthus. Despite the paradox, however, the Dianthus fully justifies its popular names, for specimens are of the most vivid carnation and others are of the most beautiful pink. Meantime the white ones are as beautiful in their way as either of their more gaudy sisters. Our studies of other flowers have made it seem commonplace enough that a plant should show such diversity. But the carnation as represented by one of my hybrid varieties, presents a color anomaly that has not been shown by any other flower with which we have made acquaintance; nor, indeed, so far as I am aware, by any other flower whatever. The anomalous plant in question is one that produces flowers that are snow white in the morning when they first open, yet which at noon are bright pink, and which, finally, toward evening assume a deep crimson color. Each flower goes through this process during the first day, but sometimes the changes in color take place a little more gradually; so that each morning one may see on the same plant carnations that are crimson, a few that are pink, and freshly opened ones of white, giving the plant a very striking and unique appearance. It chances that the plant that bears this curious flower is a most astonishing bloomer, seeming indeed to have more blossoms than foliage. So its tri-color display is indeed a striking one. The plant that bears these anomalous flowers is the hybrid offspring of a white carnation and of the deep crimson one known as Dianthus Chinensis. The plant itself is about eight or ten inches high and of quite compact growth, in these regards pretty closely resembling the Chinese parent. The foliage appears to be about an even combination of the characters of the parents. The flowers, as we have seen, combine the traits of the blossoms of the parent forms in a very anomalous way. Our earlier studies would lead us to expect that the combination of a crimson flower with a white one might produce crimson or white or pink. It would not surprise us to find hybrid plants of the same fraternity some of which bore the crimson flowers of one parent, others the white flowers of the other parent, and yet others pink flowers representing a blending of the two colors. This indeed would be perhaps what we would expect of such hybrids, if not in the first generation then in the succeeding generations. But that the color factors should be so blended that each in turn should be dominant in the same individual flower, the transition from one to the other being marked by the appearance of an intermediate color, is an anomaly for which our studies of color hereditary have supplied no analogy. We have considered it strange enough that different colors should be arranged in stripes on a flower as in the case of the four o'clock or in the new hybrid tiger flowers. But the carnation that is white at first and then pink and then crimson seems to suggest an even more curious compromise among conflicting hereditary factors. It evidences anew the curious flexibility of color schemes as applied to the petals of flowers, and presents the evidence from an altogether new angle. It may be of interest to recall, in connection with this curious manifestation of color heredity, that the carnation has been under cultivation from an early historical period. The name Dianthus, signifying divine power, is said to have been given it by Theoprastus three hundred years before Christ. The flesh color of the original carnation was broken up into red and white more than three centuries ago. Since then multitudes of varieties have been developed. Yet there is a strong propensity in this flower to hold to uniformity of color as regards any individual flower. That is to say, carnations in general are likely to be uniformly scarlet or uniformly pink or uniformly white. There are variegated forms, to be sure, but these are exceptional. This tendency of the flower to hold to one color or another may at least be recalled with interest in connection with the curious propensity of the tricolored hybrid to give recognition to the different colors of its parents in the same flower in successive periods of time. But however the anomaly may be explained, the tri-colored carnation was an interesting flower, whether considered from the standpoint of the horticulturist or from that of a student of hereditary. I have produced no other variant of corresponding interest in this tribe, although I have had twenty-five or thirty species of Dianthus growing for the purpose of crossing, and have produced some other variants of minor importance. In general, it may be said that the carnation, having been worked on by plant experimenters for two thousand years or more, presents a difficult problem for anyone who strives to develop new races of unusual value. It is like working against the traditions of the ages to attempt to modify the characteristics of such a plant in a new direction.
The experiment in which I hybridized the petunia with the tobacco plant, producing the amonaly that was described facetiously as "the petunia with the tobacco habit," will be recalled as having been described in an earlier chapter. Doubtless this experiment constituted my most interesting work with the petunia, although I have cultivated it largely and have attempted to cross it with other species, notably with the allied plant known as Salpiglosis. This plant is regarded by botanists as very close to the petunia, but I have been unable to effect a cross hybridization. It will be recalled, however, that I hybridized the petunia and the tobacco with difficulty, and it is possible that a more extended series of experiments might result in hybridizing more satisfactorily with Salpiglosis, for the plants are botanically related pretty closely. An illustration of what can be accomplished by an amateur who devotes attention to a single plant is given by the work of Mrs. Sheppard, of Ventura, California, and her neighbor, Mrs. Gould. The former took up the cultivation of flowers for the healthful outdoor life on the recommendation of her physician, and the latter became interested in the work through observation of the results achieved by her neighbor. On the advice of Mrs. Sheppard, Mrs. Gould took up the cultivation of the petunia as a specialty. The result has been that some of the finest strains of petunias that are known have been sent out from California. One of the largest and best of these is the form known as the Ruffled Giant. A great amount of time and skill are required in raising the best petunia seed, and there is still opportunity for improvement. It is particularly necessary to use good taste in the selection and combination of the colors. It is found to be, on the whole, easier to produce large flowers than those having a blending of clear, pleasing colors. There are a few common garden plants that give better opportunity for work of the amateur, particularly for one who has gained a certain amount of skill through previous experiment. The interesting character of the petunia tobacco hybrid will be recalled. Doubtless by sufficient persistency other hybrids having equal or even greater interest could be produced.
GERANIUM AND PELARGONIUM
Several years ago I brought all the geraniums that I could obtain from European and American florists and collected also some fine specimens of a variety from British America. The last named variety is exceedingly hardy, growing as far north as Alberta, where the thermometer sometimes falls 60 degrees below zero in winter. I thought it would be of interest to hybridize such wild species as this with the cultivated varieties. The pressure of other work, however, prevented me from carrying out the experiments on an expansive scale. I feel, however, that the experiment of crossing the wild and cultivated geraniums is well worth undertaking. The wild geranium is a much more promising plant to work upon, in my opinion, than was the original violet from which all our beautiful pansies have been developed. Indeed, there are few other plants among our wildlings that offer better opportunities for development. My more recent work with the geraniums has had to do more especially with the form known as the Pelargonium, a plant that is horticulturally distinguished from the geraniums, but which is obviously closely related. An interesting story is told of the way in which the Pelargonium was introduced into cultivation. A physician, experiencing difficulty in obtaining plants from foreign countries and knowing that the seeds of many choice varieties often lie dormant in the soil, commissioned a sailor to bring him a barrel of soil from the Far East-I believe from Borneo. When the soil was received and spread out and cultivated, numerous plants sprang from it, among others the one that became the parent of the now greatly prized race of Pelargoniums. Whatever the truth of this anecdote, it at least illustrates a possible way of securing new plants from foreign countries. And however the Pelargonium was introduced, it has proved a plant worthy of the fullest recognition. It has, indeed, obtained such popularity that the old-fashioned types of geraniums have in many places lost their vogue. Hybridizing the geraniums is not at all difficult when one understands the process. It is only necessary to understand that the stigma of any given flower does not mature until after the pollen of the same flower has been scattered. Bearing this in mind nothing more is necessary than to gather pollen and dust it on the stigmas of plants that have already shed their pollen. To make absolutely sure about guarding against the self-fertilization of the flower, it would of course be necessary to remove the stamens before ripening. Some of my experiments in hybridizing have been conducted with the idea of producing fragrant races of geraniums. The chief difficulty in this work is that most of the fragrant geraniums have been grown for such a length of time from cuttings that they have for the most part lost the power of producing seeds. This makes it obviously difficult to secure seeds from the plants that are precisely the ones it would be desirable to use for the purpose. Nevertheless I have produced a number of varieties having fragrance of very attractive quality. One of these fragrant varieties is developed from a compact growing Australian form which produces an enormous amount of seed. If this form were crossed with the other fragrant varieties a valuable type should be produced, as this plant has recently come from the wild and would instill vigor into the specialized and long cultivated plants. A line of work that I carried out at one time involved the crossing of the Pelargoniums with variegated leaves with those having ordinary green leaves. Among these crossbreds it appeared that the green colored foliage was prepotent or dominant over the white and yellow variations. The horseshoe variations were more readily transmitted, but there was a varying proportion of marked and plain leaves among the hybrids. I also worked at one time in selecting the geraniums for the production of large flowers of dazzling brilliant scarlet color, and with a good measure of success. One of the varieties thus produced has been greatly admired by all who have seen it, and will probably be thought worthy of introduction. It will thus appear that there is abundant opportunity for improving the geraniums even by working with the species ordinarily under cultivation. I repeat, however, that the best opportunity for work in this line will involve hybridizing experiments in which the exceedingly hardy wild species are utilized. It should be possible thus to produce new races of geraniums that have altogether exceptional quality. The wild species include some that are white in color as well as those that are pink or white striped with pink or with reddish veins. So there is opportunity to have a wide choice as to color variation. The cross might likely result also in giving the geraniums enhanced vigor so that new races of perpetual bloomers comparable to the best of pelargoniums would be produced. Few plants among all the popular favorites have greater merits than the geraniums, and none, perhaps, offer better opportunities for interesting experiments that may be made by the amateur.
-A plant which has been worked on by experimenters for two thousand years presents a difficult problem for anyone who strives to develop new races of unusual value. It is like working against the traditions of the ages to attempt to modify the characteristics of such a plant in a new direction.
This text is from: Luther Burbank: his methods and discoveries and their practical application. Volume 10 Chapter 4