THE THORNLESS BLACKBERRY-AND OTHERS
SOME TRANSFORMATIONS IN THE BRAMBLE PATCH
The nursery rhyme about the wise man and the bramble-bush will probably have little meaning for our grandchildren. For the brambles of their day will have no thorns with which to scratch out eyes-let alone scratch them in again. This, I think, is a fairly safe prediction, for the thornless blackberry is an accomplished fact, as anyone who has visited my gardens can testify; and the value of thornlessness in a berry-producing vine is so obvious that the new product can hardly fail to supplant the old type of briar bush quite rapidly. Whoever has visited a blackberry or raspberry patch of the old type and attempted to gather the fruit, will recall, doubtless, bringing away souvenirs in the form of scratches that were far more lasting than the fruit itself. When any visitor who has the recollection of such souvenirs visits my garden and sees mammoth clusters of beautiful blackberries growing on vines as smooth as pussy willows, the impression gained is both vivid and lasting that here is a plant improvement of a very notable order. In point of fact, there is perhaps no other single plant development in connection with small fruits that constitutes so radical a change and so conspicuous an improvement as the removal of thorns from the blackberry. The bush itself no longer needs the thorns to protect it against marauding deer or sheep as it did in the days when it grew in the woodland or nestled in fence corners. On the contrary, as we have elsewhere suggested, the thorns are now detrimental to the plant in that they take a certain amount of energy and building material that might be put to a better use. And from the standpoint of the horticulturist, the thorn is not merely a detriment; it is a nuisance of such significance as materially to interfere with the cultivation of the blackberry and very greatly to reduce its popularity. It may confidently be predicted that, once the thornless blackberries are generally introduced, the really delicious fruit that they bear will be seen far more commonly in the market than it has been in the past, and will soon achieve the popularity that it deserves.
HOW THE BLACKBERRY LOST ITS THORNS
As long ago as 1880, while I was still following the pursuit of a practical nurseryman and giving only incidental attention to plant development, I made experiments in the attempt to produce thornless berries. But these experiments were nearly total failures. The plant with which I worked was a blackberry bush known as the Wachusetts Thornless, which was introduced and alleged to be thornless about 1880. I raised seedlings from this plant, and also crossed it with other blackberries. But I was much preoccupied with other experiments and was greatly handicapped for means, and therefore neglected to carry the experiments to a practical conclusion. In point of fact the Wachusetts, which had been found partially thornless in the state of nature, had a goodly supply of thorns distributed here and there over the plant. It had fewer briars than most other blackberries, to be sure, but it was by no means the sort of bush to handle with impunity or rub against your face without the slightest danger, as may be done with the thornless blackberry of today. The Wachusetts was not of a really smooth stem, and it had almost nothing else to commend it. Its berries were quite small and lacking in flavor, and it had moreover the pestiferous habit of suckering from the roots. So it naturally did not achieve popularity. Nor was anything heard of any other blackberry that laid claim to thornlessness until about ten years later. Then it chanced-in the year 1902 I think it was-that Mr. David G. Fairfield, of the United States Department of Agriculture, found in North Carolina a few plants of a wild dewberry, apparently Rubus Caniadensis, that were nearly thornless. Mr. Fairchild had frequently furnished me specimens of one kind or another that he thought might be useful in my work. He now very kindly sent me a few ripe berries picked from the partially thornless dewberry. The seeds were carefully planted in boxes in my greenhouse. Of the several hundred seedlings that these produced, probably about one or two in the hundred were nearly or quite destitute of thorns. These few thornless plants were carefully selected, all the remainder being destroyed. From the fruits borne by these selected plants, a second generation was raised, from among which it was possible to select a great number that were absolutely free from thorns-showing no sign of any spicules on either stems or leaves. More than fifteen thousand seedlings were raised from the fruit of the best of these thornless plants, and out of that large number not a single specimen showed any tendency to develop thorns, every one being as smooth as the branch of an apple tree. Thus by inbreeding and selection from fruit produced by a partially thornless wild dewberry, I quickly developed a race of thornless berries that could be depended on to breed absolutely true as to thornlessness. If we interpret the facts of this development, in the light of later experience, we may infer that the condition of bearing thorns is prepotent or dominant over the condition of thornlessness in the blackberry. Thornlessness is, then, a recessive trait which will be submerged in a cross between a thorny bush and a thornless one, but which will reappear after the manner of recessive traits, in a succeeding generation, provided two individuals of mixed heritage are interbred. The fact that only a small percentage of my first seedlings grown from the seeds Mr. Fairchild sent were thornless, suggests that the flowers of the bush on which they grew had been chiefly fertilized with pollen from thorn-bearing bushes. The fruit from such a pollenization would produce thorny bushes exclusively, owing to the dominance of the factor for thorns. But if a few berries or individual drupelets of a berry had been fertilized with pollen from a flower of the thornless plant itself, these would (according to a formula with which we are already familiar) stand one chance in four of combining recessive factors and thus of producing thornless progeny. And of course from there onward the case presented no difficulty. The plant experimenter was now at hand to make sure that the thornless flowers were fertilized solely with pollen of their own sort. This of course could bring together only recessive factors, that is to say, factors for thornlessness, and the result could not be in doubt. The thorn-producing factor would be left entirely out of the composition of bushes sprung from such a union, and they would inevitably be thornless.
THORNLESS, BUT LACKING QUALITY
But while the production of a thornless race of dewberries was thus accomplished with comparative ease, once the material with which to work had been supplied, it must be understood that this was really only the beginning of the task. The original berries from which the thornless vines were grown were of no commercial value. They were small and of very indifferent flavor, to have produced a thornless race from them was an interesting scientific achievement, but one that at this stage had no practical significance. In order that the experiment should lead to the practical results at which I aimed, it was necessary now to improve the fruit of my thornless proteges. And, while something could be done in this regard by mere selection-in which case, of course, there would be no danger of having the plants backslide from a thornless condition-I soon found by experiment and observation that selection alone would be much too slow and doubtful a method for the development of such fruit as would be necessary to compete with the highly developed blackberries already in the market. For of course it could not be overlooked that the ultimate purchaser is much more vitally interested in the quality of fruit supplied him than in the question of whether this fruit grew on a thornless vine or on a briar bush. By the time I had reached the conviction that it would be necessary to adopt a more energetic procedure than mere selection in the education of the thornless berries, I had acquired through experience a very clear comprehension of the methods that must be depended on to inculcate the desired lessons. I knew that crossbreeding afforded the only feasible means of introducing good qualities into the fruit of the thornless dewberries. Now the work of development took on aspects closely comparable to those that we have already reviewed at length in the development of orchard fruits. It was necessary to bear in mind such items as increased size of fruit, good flavor, firm flesh, and time of ripening-all of these being matters regarding which the thornless berries were defective.
IMPROVEMENT THROUGH HYBRIDIZING
Of course there was no dearth of material with which to effect hybridization. The dewberry is merely a trailing variety of blackberry, and it crosses readily with all other species of blackberry. I had at hand any number of blackberries bearing fruit of the finest quality. There would probably be no difficulty whatever in producing hybrids between the little thornless berry and the Lawton blackberry, for example, or my new Himalaya berry, or any one of a dozen others. And some of these would give, among varying seedlings, a certain member that would bear excellent fruit. But, unfortunately, when such crosses were made, it was at once apparent that the thorny condition had shown prepotency, and all the seedlings that grew from thornless berries thus cross-fertilized were at once seen to be bearers of thorns. This was precisely the experience that had disheartened me, when, back in 1880, I had made the experiments with the Wachusetts partially thornless blackberry, to which reference was made above. But in the intervening time I had made many thousands of hybridizing experiments, and I now clearly understood-what at the earlier period I had known vaguely if at all-that in such a case as this we must look to the second filial generation for the kind of results we are seeking. The case is precisely comparable to that of the white blackberry, for example, or to that of the stoneless plum. When the white blackberry is crossed with a black blackberry all the offspring of the first generation are black. And when the stoneless plum is crossed with the stone-bearing plum all the offspring of the first generation are stone-bearers. But in each of these cases the succeeding generation will show individuals in which the submerged character reappears-we shall have white blackberries and stoneless plums again. So I had every reason to believe that a comparable result would be achieved if the thorny hybrid seedlings born of my thornless race were given opportunity to redeem themselves in their progeny. The expectation was justified. In the second filial generation the thorny seedlings produced a certain proportion of thornless progeny. And these thornless bushes now bore fruit far superior to that of their thornless grandparent. They had inherited some of the good fruiting qualities of their thorny grandparent, even though they had repudiated his thorns. This was obviously encouraging. So the experiment was continued along the same lines through successive generations. I selected, of course, the specimen in each generation that showed the best combination of desired qualities and hybridized, in successive generations, the Lawton blackberry, the giant Himalaya, and various others, to gain size of berry, earliness of bearing, new flavors, more acid, and, in a word, to supply whatever defects could be discovered. The original thornless berry was a late bearer, and its fruit lacked size, spiciness, and refreshing acidity. But these qualities were supplied in good measure through successive crosses. One seedling in particular, grown in 1906, showed exceptional qualities, and the subsequent stock was largely grown from the fruit of this single bush. Like its fellows, it bore strains of half a dozen races of high-grade market berries, blended with the thornless strain. Of course each successive hybridization with a bearer of good fruit meant the introduction of thorns in the seedlings of the next generation. This was inevitable, since of course all the bearers of commercial blackberries were bearers also of thorns. The Himalaya in particular is an exceedingly thorny bush, and the otherwise commendable Lawton is an almost equal offender. But whereas these thorny shrubs were prepotent in their influence over their direct offspring as was expected, some of their grandchildren always reverted to the thornless state. And so here as in various other experiments already described, advance was made by indirection. We are forced to seesaw back and forth in successive generations between thorny bushes and thornlessness; yet on the whole there was progress, inasmuch as each successive generation showed better qualities of fruit, and each alternate generation the recurrence of the thornless condition. Inasmuch as the thornless bushes, of whatever generation, will breed true to thornlessness if fertilized among themselves, it is obvious that each thornless generation constitutes a fixed race, provided the plant experimenter does not elect to disturb its fixity by a new hybridization. The result, up to date, is that after twenty years of selective breeding along these lines, the descendants of the little North Carolina dewberry (who are descendants also, of course, of various and sundry berries of more aristocratic bearing) constitute a race of blackberries growing on large, well-shaped, spreading bushes that are absolutely thornless. The fruit itself is a large, handsome, glossy black berry, of excellent flavor, profusely clustered-a fruit that makes inviting appeal to the wayfarer and which will exact no penalty in the way of scratches from those who gather it. I have told thus at length the story of the thornless blackberry, because the development of this fruit quite eclipses all my earlier work with the blackberries, and makes the record of the development of the thorny varieties, however excellent their fruit, seem an almost archaic performance. It must be recalled, however, that the present thornless blackberries of quality could not have been secured so expeditiously had not material been at hand for the hybridizing experiments through which size and flavor were bred into the fruit until, as just related, the perfected thornless varieties were developed. And this material was largely the product of earlier experiments through which blackberries of the old type had been improved as to their fruiting qualities. It is necessary, therefore, in the interests of completeness, to retrace our steps and briefly to review the earlier experiments-some of which, indeed, were carried forward coincidently with the development of the thornless-through which new races of blackberries of exceptional quality, though still handicapped by thorns, were developed. In connection with this story it is interesting to recall that the cultivated blackberry is essentially an American product. No other country until quite recently has appreciated the quality of this fruit sufficiently to cultivate and develop it. Wild species, to be sure, are abundant in Europe, growing everywhere in England and in Ireland, along hedges and in waste places; but the horticulturist has all along seemingly been prejudiced against the fruit, partly perhaps because of its offensive briars. The prejudice against the wild bramble was retained by the Colonial settlers of America-retained so persistently that fully two centuries were needed for this excellent berry to make its way into the fruit gardens. Not a single horticultural variety of blackberry was introduced until almost the middle of the nineteenth century. Then the Dorchester was brought to notice, and about a decade later a better berry, the Lawton, which is still a standard, and two other varieties, the Holcomb and Wilson's Early, were brought to the attention of fruit growers. As a significant industry, blackberry cultivation is even more recent. It has almost wholly developed since 1870. It began with planting, on a commercial scale, the Lawton, which was later supplanted by the Kittatiny in some sections. This in turn gave way to the Snyder, and still more recently better varieties were developed. The evolution of the fruit had been gradual, but it has at last established a place in the horticultural ranks. I repeat my prediction that it will gain a new impetus now that the one great drawback of the blackberry, its thorny stem, has been eliminated. It will take some time, however, to spread the thornless berry universally, and in the meantime the blackberries of the older type retain a measure of interest.
MATERIALS FOR DEVELOPMENT
The chief American wild species, which furnished material for the development of the races just named, are the common Eastern blackberry (Rubus nigrobaccus), familiar everywhere throughout northeastern America, and a closely related form, considered by some botanists a mere variety, known as Rubus sapivus. The common wild plant is an upright grower, stout, has little recurving canes that are usually deeply furrowed lengthwise, and clothed with stout more or less hooked prickles. The other species or variety is slightly more erect, with fuller and firmer canes, differing somewhat also as to shape of leaves. It bears berries that are usually rounded, generally soft and juicy, and of superior flavor. At my old home in New England this variety grew abundantly on sandy soil, being one of the best wild blackberries in that vicinity. I early noticed that this plant was inclined to vary widely. For example, the vines, although usually stiff, upright growers, sometimes more resembled the common blackberry, or even tended to take on the trailing habits of the dewberry. When I came to know more about plant development I recalled this tendency to variation, and felt that here, as always, a fruit of this tendency should furnish material for the development of improved varieties. In due course I worked with the various cultivated varieties of blackberry, and soon developed some improvements, particularly with reference to the size of fruit, its flavor, and lengthening the season of fruit bearing. One of the improved varieties with which I worked had been lately introduced under the name of the Early Harvest; another was named Wilson Junior. But my most notable results attended the use of the native species, and in particular the introduction of foreign species from remote parts of the earth. As early as 1879 I was earnestly working on varieties of blackberries, and of raspberries as well, that were obtained from my collector in Japan, combining these with other wild and cultivated varieties from various sources. My first really notable success, however, came about through selection, without the aid of hybridizing, from a berry that I introduced from India. This berry, in recognition of its origin, was named the Himalaya, sometimes shortened to Himalya.
THE PROLIFIC HIMALAYA
The seed from which this improved blackberry grew was obtained from India through exchange. It would appear that transplantation to an altogether new soil and climate had the same stimulating effect upon this blackberry that we have seen manifested in the case, for example, of the Japanese plum, the New Zealand winter rhubarb, and sundry other plants. For there appeared among seedlings of the second generation an individual that showed a very marked improvement over its parents. This exceptional seedling was cultivated and propagated, and its qualities proved so unique that it was introduced in 1885 by a special circular, being christened, as just stated, the Himalaya. After the usual decade or so of probation, during which every new fruit of whatever quality must wait for recognition, the Himalaya took its place, first on the Pacific Coast, and later throughout the northern and central states, as a standard blackberry. After it came to its own, so to speak, its popularity was so great that for several years the plants could not be multiplied fast enough to meet the demand. It is a plant of extraordinary vigor. A single cane may grow more than twenty-five feet-sometimes even fifty feet-in a season, and attain near the base a diameter of an inch to an inch and a half. The aggregate growth of cane of a single plant in a season may exceed a thousand feet-one fifth of a mile. And in point of fruit production, the Himalaya far surpasses any other berry plant ever grown. Reports tell of a single bush bearing two hundred pounds of berries in a season. "My daughter and I picked fifty pounds of berries from one Himalaya bush the latter part of August, 1906," writes one enthusiast, "and we scarcely missed them from the bush. This was after many others had picked from the same bush. I picked three pounds standing in one position. I could have picked double that amount if I could have reached into the bushes farther, but the entangled branches with their sharp thorns prevented me." The narrator adds this comment: "It is my opinion that if this bush were properly pruned, fertilized, and irrigated, as well as shaded from the extreme heat of the sun in July and August, it would bear between three and four hundred pounds in a season." Such a report is typical. The prolific bearing of the Himalaya is the subject of astonished comment from everyone on seeing this extraordinary vine for the first time. The fruit itself is of medium to large size, unusually sweet, and spicy, with small seeds, and fine in quality. The berries grow in clusters sometimes a foot or more across, and they continue to ripen after most other blackberries are gone. If not pruned, the vines of the Himalaya will grow to a length of one hundred feet or more, like grape vines. They appear to be absolutely resistant to disease, and they have recently shown the ability to resist the extreme cold of Michigan and the far northern states. It should be known that the Himalaya takes a year or so more to come to its best bearing condition than ordinary blackberries, but when in full bearing a single plant will produce as much as a dozen ordinary blackberries. The elimination of the thorns is a matter to which sufficient reference has already been made. As to abundant bearing, nothing more is to be desired. The Himalaya at present produces all the berries that a vine can possibly support.
DEVELOPMENT THROUGH HYBRIDIZATION
As the experiments in the development of the blackberries continued, I quickly passed from the stage of mere selection to that of crossbreeding and hybridization. The plants utilized in these experiments included not only all types of native blackberries proper, and numerous foreign species, but plants of the allied race of dewberries. The dewberry, to be sure, is closely related to the blackberry; it is, indeed, a blackberry that has assumed a trailing habit. Or possibly the case would be stated more truly if we say that the bush of the blackberry is a dewberry that has risen from the ground and assumed the habit of upright growing. There is, nevertheless, a sufficient divergence to make the dewberry seem to casual inspection a plant of distinct type. And, at the time when my experiments were begun, there were probably few plant developers who would have supposed it possible to hybridize even the dewberry with the ordinary blackberry. Successive crosses were effected, nevertheless, at an early stage of the work, and in the course of my experiments the interblendings were so numerous and intricate that seedlings were produced showing all gradations of habit between the trailing vine and the upright one; as well as all gradations of leaf and fruit form and quality. Sometimes in crossing a blackberry with a dewberry the trailing habit is greatly intensified, the hybrid being a long, vine-like, straggling plant. Again, the result may be just the opposite, a tall, upright, almost tree-like plant being produced. Some hybrids would run a distance of at least fifty feet. Others, perhaps of the same fraternity, would take on so tree-like a habit that their fruit could be reached only with the aid of a stepladder. But perhaps the most singular and interesting anomaly was that some of these hybrids bore flowers and fruit in every month of the year, though sparingly. At the time when I had a large colony of blackberry-dewberry hybrids, ripe berries could be picked from one bush or another almost every day of the year. The possibility of producing, with the aid of such hybrids, commercial varieties of blackberries that will fruit at all seasons is inviting. Experiments already far advanced have greatly extended the blackberry season, and there is reason to expect that the blackberry lover in the future will be able to secure this fruit, in one variety or another, from early spring until almost the onset of winter. As to other possibilities of blackberry development, something was said in the earlier chapter that described the development of the white blackberry. But much remains to be told. The chief development, however, through which not merely new varieties but new species of berries have sprung from the amalgamated stock of the forty-odd species of bramble fruit with which I have experimented, have had their origin in hybridizations that linked the blackberry with its relative the raspberry. The account of the altogether notable results that have arisen from this alliance is an integral part of the story of the blackberry. But it may be told to best advantage in connection with the story of the raspberry in the succeeding chapter.
-The thornless blackberry is an accomplished fact, and the value of thornlessness in a berry producing vine is so obvious that the new product can hardly fail to supplant the old type of briar bush quite rapidly.
This text is from: Luther Burbank: his methods and discoveries and their practical application. Volume 6 Chapter 1