The Winter Rhubarb
MAKING A CROP FOR A HIGH PRICED MARKET
More than one enthusiast has declared that the most important garden vegetable that has been introduced to the world in the past half century is the giant winter rhubarb. This no doubt is an over estimate, if for no other reason than that it overlooks the Burbank potato. Still, there is no question that my winter rhubarb has proved to be of very great economic importance. Although introduced quite recently, it has already made its way to all quarters of the globe, and it has proved of unusual value in regions where no other rhubarb had hitherto been, or could be grown. At the Cape of Good Hope, for example, efforts to grow rhubarb had been made for a century at least, and always without success; but the new variety proves an especially satisfactory crop there, as elsewhere, in warm, arid climates The plant has aroused very unusual interest in conservative Great Britain, where the older varieties thrive and have been extensively grown specimens having been obtained direct from my plantation by Robert Holmes, a member of the Royal Horticultural Society, and others. The royal gardens of England are now supplied with it. Meantime the Emperor of Japan and the King of Italy obtained it directly from my gardens, and the plant has been taken back to its original home in New Zealand, whence the original stock came, and in its improved or, one might better say, metamorphosed condition, it now finds favor there, whereas its ancestral form was justly regarded as a plant of no importance.
THE QUALITIES OF THE NEW RHUBARB
It must not be supposed that this widely extended approval of the rhubarb is dependent on any mere caprice. It is based on qualities of the most enduring and substantial character. Otherwise, it would not have been possible to plant thousands of acres of this crop in California and to find a ready market for the entire product in the eastern United States. In point of fact, so eager has been the market that the rhubarb has been quite often called by its growers the "king mortgage lifter." More than one substantial fortune has been made by growing it here in California and shipping it to the eastern States during the holiday season when fruits and green vegetables are relatively scarce. It retains, as to general appearance, the aspect of a greatly enlarged stalk of the familiar rhubarb or pieplant of the eastern vegetable garden. But the stalks are of a characteristic rich crimson color, and as brought to the table the sauce made from them is not only delicious in flavor, suggesting the strawberry and raspberry, but it is quite devoid of the stringiness or fiberlike texture and the disagreeable "ground taste" of the ordinary pieplant. Many people who have hitherto regarded pieplant as a plebeian dish to be avoided are enthusiastic in the praise of the new product. The crimson winter rhubarb produces not only far larger stalks than the old New Zealand prototype, but at least ten times as many of them to each plant. The stalks begin to appear in great abundance early in September and continue to produce a product of unvarying quality for eight to twelve months together-in California throughout the entire year-instead of for a few weeks in the spring. So the popularity of the winter rhubarb from the standpoint of the grower as well as of the dealer and consumer, is not hard to understand. It may be added, as further evidencing the unusual qualities of the new plant, that it grows in almost any soil, although giving quick response to good conditions of cultivation like the older varieties; that it propagates readily from root division and under these circumstances breeds altogether true to the perfected type; and that it is hardy and requires no unusual attention, so that any amateur may grow it in his garden even more readily than he grows the ordinary rhubarb. It must be understood, however, that the plant cannot thrive in latitudes where it is buried under snow, as the steady production of leaves appears to be essential to its very existence. In the colder parts of California it does indeed cease to grow actively in the heart of winter, but even then it submits to adverse conditions reluctantly, if the phrase may be permitted; that is, that it stops putting forth new leaves only when the conditions are exceedingly unfavorable and immediately resumes new growth when the slightest change for the better in the weather occurs.
THE ORIGIN OF THE WINTER RHUBARB
The importance of the new plant, and its wide departure from the traditions of the rhubarb family, might lead one to suppose that the production of the new variety had been a task of great difficulty. Perhaps from the standpoint of the average plant breeder it could hardly be said that its creation was altogether easy; yet compared with some of my other plant developments the production of this one was at least relatively simple. The original stock from which the new variety was developed, came to me from the antipodes. It was sent by the firm of D. Hay & Son from Auckland, New Zealand. The first two or three shipments were lost, as the plants died on the way, but at last I obtained half a dozen very diminutive roots that showed some signs of life. These, as anticipated, produced stalks during the winter instead of following the conventional rhubarb custom of putting forth stalks for only a few weeks in the spring. The stalks of this original winter rhubarb, however, were very small-about the size of an ordinary lead pencil-and certainly not worth cultivating for immediate use, as they would have proved quite unmarketable. The plant was admitted to have no great value in New Zealand. Indeed, in point of quality of stalk the imported plant bore no comparison with ordinary pieplant of our gardens. It was solely and exclusively the quality of winter-bearing that made the plant appeal to me and suggested to me the possibility of developing from it a valuable addition to our list of garden vegetables. My original stock of half a dozen plants soon increased to a hundred or more. These plants produced seed abundantly in successive years, and all this seed was carefully planted and the seedlings that grew from it, to the number of hundreds of thousands, were closely examined and tested as to various desirable qualities. From among the thousands I was able to select here and there a plant that showed exceptional qualities of growth, standing well up above its companions of the same age. Of course selection was made of the plants showing this exceptional virility, and in the course of a few years I had thus developed, by persistent selection, a race of plants that grew with extreme rapidity, and to a size, by comparison, quite dwarfing that of the original parent stock. These fast-growing descendants of the New Zealand plant had not only the desirable qualities of texture and flavor of leaf stalk already referred to, but they retained and advanced upon the tendency of their ancestors to grow constantly throughout the year. This anomalous tendency, rather than the improvement in the other qualities of the plant, is obviously the one that requires explanation. Remarkable improvement in size and in other desired qualities through selection, is a more or less familiar method of plant development. But the production of a race of pieplant that departs radically from the most pronounced and characteristic trait of the rhubarb family, namely brief period of bearing, is something that requires explanation. A clue to the explanation is found when we recall that the plants were sent me from a region lying on the other side of the equator. The plants were exceptional even there in that they had shown a tendency to bear-that is to say to produce juicy leaf-stalks-during the cold season. Through some unexplained freak of heredity or unheralded selective breeding, they had developed a hardiness that had enabled them to put forth their leaves much earlier than is customary with all other races of rhubarb. The difference was only a matter of weeks, and was of no greater significance, perhaps, than the observed difference in time of bearing between different varieties of other vegetables and fruits. Everyone knows that there are early and late-bearing varieties of most commonly cultivated vegetables and fruits-summer apples and winter apples furnish a familiar illustration. Perhaps someone had discovered a root of rhubarb that chanced to have peculiar qualities of hardiness, and had propagated it until he had a variety that began bearing while the relatively mild New Zealand winter was still in progress. But this is only the beginning of the story. The sequel appears when we reflect that the season that constitutes winter in New Zealand is coincident with the summer time of the Northern Hemisphere. So when we say that the crimson rhubarb was productive during the winter in its original home, this is equivalent to saying that it had the habit of bearing during our summer time. Transplanted to California, the New Zealand product continued to put forth its stalks, quite in accordance with its hereditary traditions, during what, according to its ancestral calendar, was the winter season, although the climatic conditions that now surrounded it were those of summer.
THE INFLUENCE OF ENVIRONMENT
But meantime this plant, like every other living organism, was of course subject to the directly stimulative influence of its environment. Its hereditary traditions had developed what we may speak of as an instinctive tendency to grow at a given time of year regardless of climatic conditions; but they had also given it an equally powerful tendency to respond to the stimulus of cold weather, and to become productive not merely in the season of winter but under the climatic conditions of winter. In other words, the combined influences of heredity and of immediate environment were here as always influential in determining the conditions of plant growth. But, whereas in New Zealand the environment of winter-characterized by cold temperature-coincided with the calendar months of June, July, and August, in the new environment of California the conditions of winter were shifted to the calendar months of December, January, and February. So the two instincts, one calling for productivity in June, July and August, and the other for productivity during cold weather, were now no longer coincident, but made themselves manifest at widely separated seasons, thus producing a perpetual rhubarb. So the net result was that, merely through the retention of old instinctive habits under the transformed conditions imposed by migration to the Northern Hemisphere, the winter-bearing rhubarb of New Zealand was transformed, by most careful and persistent selection, into a summer-and winter-bearing plant in California. And inasmuch as there are no sharp lines of demarcation as to just when the pieplant begins and ends bearing, the two seasons tended to merge, with the practical result that some of these plants became all-the-year bearers.
THE POWER OF HABIT
Possibly the use of the words habit and instinct as applied to a plant requires a few words of elucidation. We ordinarily take the habits of a given plant so much as a matter of course that we are prone, perhaps, to overlook their close correspondence with the habits of birds and animals and other animate creatures. Yet a moment's consideration will make it clear that we may with full propriety speak of the fixed or regular "habits" of plants, and that there is no logical reason why we should not speak of them as being determined by "instinct," which after all suggests only the spontaneous response to environing conditions, present or reflected through heredity. And the force of the various instincts or habits, in the case of the plant, as in the case of birds and animals, is overwhelmingly powerful and quite beyond the possibility of change in any given generation. To cite a single illustration from the case in hand, every gardener knows that he cannot by any process of cultivation make the ordinary rhubarb plant change its fixed habit of spring production. No amount of coaxing and no manner of soil cultivation or fertilization can take from the rhubarb the impelling force of the hereditary tendency to put forth its stalks in the spring time rather than in summer or fall or winter. And a similar fixity of habit characterizes in greater or less measure, most other familiar cultivated plants. Artificial selection has extended the season in certain cases, and early or late-bearing varieties have been developed as already noted; but for each variety the habit of producing at a given time of year is one of the most fixed and, as regards any given generation, unalterable of tendencies. Recalling this it will not seem strange that the Australian winter rhubarb retains its habit of winter production notwithstanding the fact that it had been transplanted to a hemisphere where the climatic conditions of its winter were diametrically changed.
ILLUSTRATIONS FROM BIRDLAND
Perhaps the all-importance of this inherent tendency to gauge habits in accordance with the calendar will be more clearly apprehended if we cite an illustration from another branch of the organic world. Take the migrations of birds as a familiar instance. If you watch the birds at all, you have doubtless noted that the migrants that come to temperate regions from the tropics arrive each spring in your neighborhood at a date that you may fix in advance with almost entire certainty. The hardier birds, to be sure, such as the robin, the blue-bird, and the meadow-lark, retire before the blasts of winter somewhat unwillingly and they begin their northward migration at a period that may vary by a good many days or even weeks according to the forwardness or backwardness of the season. But the coterie of tender birds-orioles, vireos, wood-robins, tanagers, fly-catchers-which spend the winter in the region of the equator, must begin their northward migration without regard to the climatic conditions, inasmuch as their winter home is a region of perpetual summer. They start northward merely in obedience to an instinctive time-sense that has been implanted through long generations of heredity, and they move across the zones with such scheduled regularity as to reach any given latitude almost on a fixed day year after year. In Massachusetts or New York or in Ohio or in Iowa, for example, you will find the last flight of migratory birds, comprising the various species of wood-warblers and vireos, the orioles, and the scarlet tanager, making their appearance between the tenth and fifteenth of May each year, quite without regard to the advancement of the season. And a few months later you will note, if you are observant, that these and the other migrants disappear in the fall, having taken up their return voyage at about the same calendar period year after year, although in one season the September days may be as hot as August and in another season they may have the chill of November. Countless generations of heredity have fixed in the mechanism of the bird's mind the instinct that impels it to migrate at a fixed season; and no transient or variable conditions of the immediate environment can alter that instinct, even though, in a given case, its alteration might be vastly to the advantage of the individual.
EVEN UNTO DEATH
As proving the latter point, and as further illustrating the force of the instinctive time-sense under consideration, let me recall the case of the martins to which reference was made in an earlier chapter-the case in which these birds starved to death because in a particular season drought prevented the hatching out of their insect food. Everyone knows that the martin is a bird of very swift and powerful flight. Its estimated speed is more than a mile a minute, and it habitually remains hour after hour on the wing. It was easily within the capacity of the martins that starved to death in New England to have shifted their location at the rate of something like two or three thousand miles a day. And assuredly within half that distance, probably within two or three hundred miles at the most, they would have found an abundant supply of food. Now the season at which the martins actually starved was August; only a few weeks, therefore, before the time of their regular autumnal migration. Had the birds lived another month they would instinctively have begun a long journey to the south, and a single night's flight would have brought them to regions where no doubt their food needs would have been abundantly supplied. From a human standpoint, it would seem only natural that the birds, deprived of food, should have begun their seasonal migration a few weeks before the usual time; whereby their lives would have been saved. Whoever understands the force of hereditary instinct will realize that such a departure as this was for the birds impossible. The instinct of migration comes to the martins in September, not in August, or at least not in early August. The habit of migration is no more determined by any conscious judgment of the bird than is the habit of spring growth determined by a conscious judgment of the rhubarb. The force of untold generations of ancestors impelled the martins to remain where they were, even though starvation was the penalty. Wings they had, with which they might have sought and found a new environment where food was plentiful; but they were powerless to use the wings at this particular season, because the particular week had not arrived at which the hereditary clockwork of their organisms would strike the hour for migration. Taken by and large, it is better for the race of martins that they should not migrate until September; this fact had been established through the test of thousands of generations, and the result was registered indelibly in the organism of every bird. Were it possible to destroy the racial tradition in the interests of any single generation, the life-habits of the species would become so variable and desultory that racial continuity would be endangered. So the individuals of a generation throughout a large region were sacrificed to a racial instinct which in the main was beneficial to the species. It will be clear, I trust, how this illustration bears directly on the case of our winter rhubarb.
RESTORING SUBMERGED INSTINCTS
It could make no difference to the roots of this plant that they had been unwittingly transplanted from a land where winter comes in July to a land where that month betokens summer. The instinct of bearing at that particular season had all the force of the instinct that impels the bird to migrate at a given time; and this instinct could by no chance be repressed in a given generation, any more than the martins could make over their migratory instinct to fit a transitory condition. But all this leaves quite unexplained the other fact, which bore so important a part in our story, that the New Zealand rhubarb-when transplanted to California assumed a new habit of bearing during the cold season of the Northern Hemisphere which corresponded to the summer of its original habitat and therefore to a calendar period at which its immediate ancestors had been accustomed to assume a condition of dormancy. How is our theme of the power of instinctive habit to be made to coincide with this seemingly illogical departure? Our answer is found, as it has been found in the explanation of other anomalies of plant development, in an appeal from the immediate ancestry of the rhubarb to the countless galaxies of its vastly remote ancestry. We have already pointed out that all plant life traces back its origin, if you go far enough, to the luxuriant tropical vegetation of the Carboniferous Era. But in the case of the rhubarb it is not necessary to go back so far as this to find an ancestry habituated to tropical conditions. In point of fact the rhubarb is, in all probability, a tropical plant that has but recently migrated to temperate zones-using the word recently in the rather wide sense necessary when we are dealing with questions of racial development under natural conditions. In other words, it is perhaps only a matter of a few hundred generations since all the ancestors of the existing rhubarb tribes were growing in the tropics, and hence, like tropical plants in general, were all-the-year bearers. In more recent generations, this habit of perpetual bearing has been modified, in case of the rhubarb as in case of nearly all plants of temperate zones, to meet the altered conditions of a climate in which summer and winter alternate. To adapt themselves to this change of climate, plants were obliged to go into retirement in the winter season, and natural selection preserved only the races that showed this adaptability of habit. Thus the common race of spring-bearing rhubarb, as we know it, was developed. But the latent capacity to bear at all seasons-to live a fully rounded life throughout the year-which may be considered the normal and inherent propensity of all living things, and which is observed to be the habit of tropical plants in general, was never altogether lost. Submerged generation after generation and century after century, the hereditary factors that make for perpetual growth were still preserved, capable, under changed conditions, of being resuscitated and of making their influence manifest. The changed conditions came, in case of the rhubarb, when the plant found itself in the new environment of California. New soil, new atmosphere, new climate-all these are stimulative. Then successive generations of the plants were bred from seeds, and we have already seen that the mixture of strains thus effected tends to have a disturbing influence on the germ plasm, permitting new combinations of characters and resulting in the development of new forms. We saw this in the case of the Shasta daisy and very notably in the case of the hybrid walnuts. We shall note the same thing again and again in connection with a multitude of other plants. In the case of the rhubarb, the response was almost immediate. Artificial selection enabled the plants that manifested the atavistic tendency in largest measure, to propagate their kind. And thus, in the course of a few generations-though not without making selection among hundreds of thousands of individuals-I was enabled to assist the plant to bring to the surface the long submerged tendencies that impelled it to grow fast, to grow large, and to grow perpetually.
NO NEW PRINCIPLE INVOLVED
And thus the crimson winter rhubarb as it finally came to perfection in my gardens is accounted for. In developing it, no new principle was invoked, no new method even. I merely took advantage of opportunities afforded by the translation of the plant from one hemisphere to another, and aided the plant in putting forth potentialities that had long been repressed but which still stubbornly persisted as latent factors or submerged tendencies in the racial germ-plasm. Perhaps the matter seems rather complex as thus explained; and indeed all matters pertaining to living organisms are complex in the last analysis. But the methods of operation were in practice simple. Granted certain conditions and certain hereditary tendencies; granted, in other words, the materials with which to work, it required only clear-eyed selection and patient waiting-the encouragement of some tendencies in the right direction and the suppression of other tendencies in the wrong direction-to produce the desired result.
PROPAGATING THE WINTER RHUBARB
To make the story complete, however, it should be recorded that, although the winter rhubarb was developed by mere selective breeding of a pure strain, yet the experiment was not carried forward without numerous tests of the hybridizing method. From the outset the New Zealand plant was crossed with the native rhubarb, hoping thus to stimulate variability. And, almost needless to say, variability was stimulated. The hybrid plants took on sundry forms and diverse habits. But it chanced that no one of these forms was an improvement on those that were secured by selection from the pure New Zealand stock. Nor did this New Zealand stock, even when developed into my new all-the-year bearer, prove capable of sure propagation from the seed. It can readily be propagated by dividing the roots or by cutting out little sections of the root containing a bud, so there is small necessity of development from the seed. But in this case, as with so many other cultivated plants, it is essential to use this method of propagation if we wish to have an absolutely fixed variety. An obvious explanation would be that the original New Zealand rhubarb was of mixed racial strains. This, indeed, would account for its tendency to vary, and contribute to its successful development in California. The inter-breeding which produced the winter-bearing strain, may have been done quite by accident in New Zealand, the plants that came to me embodying the full possibilities of development without further hybridizing.
PERPETUAL BEARING NOW FIXED
It should be added, however, that even when grown from seed, the new winter rhubarb always manifests the tendency to perpetual bearing. This one trait is fixed, though some of the other qualities of the plant are still variable. Using the new terminology we may say that the tendency to winter-bearing is a unit character that is latent or recessive, and that the winter rhubarb has no factors of the opposite trait of limited bearing and therefore cannot revert so long as it is inbred. When crossed with the spring-bearing race, however, the offspring sometimes revert to the old habit, as might be expected. As already noted, nothing is gained by such crossing. Nor is there any necessity for the growth even of pure-bred seedlings. Propagation by root-division answers every purpose, and, thus multiplied, the new crimson winter rhubarb, in its perfected varieties, constitutes a fixed race and is a permanent acquisition to the list of garden vegetables.
-It required only clear-eyed selection and patient watching-the encouragement of tendencies in the right direction and the suppression of tendencies in the wrong direction-to produce the result.
This text is from: Luther Burbank: his methods and discoveries and their practical application. Volume 2 Chapter 6