Chapter II: Botanical and Horticultural Classifications of the Peach (2)

This plant grows wild on rather barren mountain slopes at about 3000m. altitude north of the town of Tachienlu on the China-Thibetan borderland, where it was first detected by me on July 9, 1908, and from whence I introduced it by means of seeds in the autumn of 1910. I saw only a few trees, but have reason to believe that it is fairly common, and also that it is thereabouts cultivated for its fruit. In the Arnold Arboretum this species has proved no more hardy than the Common Peach, though from the altitude at which it grows naturally it ought to be the hardier plant. Our largest specimen is 2.5m. high and crown 3m. through. It starts into growth and leafs out much later than the Common Peach, and is therefore much less liable to be affected by late frosts. This is the one advantage so far evident in our experience with this new Peach under cultivation. Undoubtedly it possesses important horticultural possibilities, and especially should it be valuable to the hybridist on account of its small and smooth stone. Indeed, it requires no imagination to realize the advantage to be gained by supplanting in our present day race of garden peaches for the large and deeply furrowed stone one that is quite smooth and small."

_Prunus mira_ is now under cultivation at the Arnold Arboretum near Boston, in the parks at Rochester, New York, on the grounds of this Station and at Brookville, Florida, in charge of the United States Department of Agriculture. No doubt within a few years we shall have positive evidence of its horticultural value.

PUBESCENT-FRUITED SPECIES OF PRUNUS FROM THE UNITED STATES

Seven pubescent-fruited species of Prunus are found in the Southwestern States. From reading the descriptions, it is hard to tell whether these plants, unique in more than one respect, are most closely related to peaches, plums, apricots or almonds. Professor S. C. Mason of the United States Department of Agriculture, who has studied these fruits,[181] thinks that some if not all of them may have horticultural value, at least in the Southwest where fluctuations of heat and cold are great and drought and alkalinity of soil must be endured by plant-life. They deserve brief mention in _The Peaches of New York_ because of the possibility that some of them can be used as dwarfing-stocks for the peach and possibly that some may be hybridized with cultivated peaches. The species, with brief notes taken for most part from Mason, are as follows:

_Prunus texana_ Dietrich, the "wild peach" of Texas, is a plum-like fruit from eastern Texas of which there are already several hybrids with the wild plums of the region. _Prunus andersonii_ Gray is the "wild almond" or "wild peach" of Nevada. The species is found in western Nevada and eastern California in a region subject to severe cold in winter and extreme drought and heat in summer. One cultivator of this species suggests it as a good stock for the peach and the almond and thinks it has possibilities for hybridization.[182] The "desert apricot," _Prunus eriogyna_ Mason, comes from a very restricted region in southern California. The characters of this species should fit it to endure the environment on the desert slopes of mountains. The "desert almond," _Prunus fasciculata_ Torrey, sometimes called "wild peach" and "wild almond," ranges much farther south and east than _Prunus andersonii_ in southern Nevada and southern California, crossing into southwestern Utah and northwestern Arizona, and grows in gravels and sands where its roots penetrate to great depth. _Prunus minutiflora_ Engelman, the "Texas almond," is found in southwestern Texas, a shrub which, like the former species and the one following, is dioecious, a marked and unique peculiarity of these three species. The "Mexican almond," _Prunus microphylla_ Hemsley, is found in the high mountain region of Mexico. _Prunus havardii_ Wight, is known only in a restricted region in western Texas. The last two species are so little known that one cannot even surmise whether they may have horticultural possibilities.

HORTICULTURAL CLASSIFICATIONS OF THE PEACH

The opening years of the Nineteenth Century mark the first attempts at classifying peaches. By 1818 as many as three classificatory schemes had been proposed, all being modifications of the same general arrangement. July 7, 1818, John Robertson read a paper on classifying peaches and nectarines before the Horticultural Society of London. Later, this was printed in the Transactions of the Society[183] together with a classification by M. Poiteau from the _Bon Jardinier_ and another by Count Lelieur from his _Pomone Francaise_. In January, 1824, George Lindley read before the same society a classification which was but an extension of the older arrangements.[184]

Robertson separated peaches into true peaches and nectarines and these in turn into Classes, Divisions and Sub-divisions. He founded the two classes on the presence or absence of glands; for each of his classes he made two divisions distinguished by the size and color of the flowers; each of the four divisions is once redivided into a sub-division in which the flesh parts from the stone and another in which the flesh adheres to the stone. The two French writers use the same characters but found their second division on the adherence or non-adherence of the flesh to the stone; their third on the size of the flower but making three partitions as to size; and their fourth on the presence or absence of glands which they divide into globose and reniform. Lindley created three classes dependent on the presence or absence and the character of the glands and the character of the serrations; three divisions of each class in accordance as to whether the flowers are large, medium-sized or small; two sub-divisions of each division to agree with the presence or absence of down; and for each sub-division two sections, one for clingstones and one for melters.

This was the age of the classifier and other classifications, all similar in plan, rapidly followed in England, France, Belgium and Germany. No one at this time seems to have attempted a natural classification of peaches.

Of the nine leading American pomological writers of the Nineteenth Century, Coxe, Prince, Cole, Hooper, Elliott and Barry either do not attempt to classify or make but one or two simple divisions. Kenrick, 1832, follows Lindley in part but makes use of season in his classification. Downing in his first edition, 1845, divides peaches into freestones with pale flesh, freestones with deep yellow flesh and clingstones. This simple arrangement by Downing is notable only because it is the first time color of flesh is made use of as a distinguishing mark, the Europeans probably not having done so because yellow-fleshed varieties are rare in Europe whereas in America they are as common or more so than white-fleshed sorts. Thomas, in 1846, did not classify but in later editions divided peaches into two divisions, founded on adherence of flesh to the stone; two classes for each division in accordance with color of flesh; and three sections founded on leaf-serrations and glands.

These Nineteenth Century classifications are artificial. That is, they single out a few points of resemblance and difference and arrange varieties in accordance with them, convenience and facility of use being the controlling principles. They are natural to a degree, however, because varieties agreeing in one point of structure commonly agree in other characters. With the peach, more than in the artificial classification of most other fruits, the characters are readily distinguished and are stable. Yet most English pomologies now arrange varieties of peaches alphabetically, while the American texts do the same or use the pseudo-natural system of Onderdonk. His classification we are about to discuss. The early artificial arrangements failed to stand the test of time because classifiers could not agree upon any one arrangement and added confusion by the multiplicity of them; and, because the new varieties of the last half-century, coming in great numbers, are so poorly described that the great majority of them could not be classified from the data at hand.

In 1887 Gilbert Onderdonk,[185] a special agent of the United States Department of Agriculture, published a natural classification of peaches.[186] He put varieties of peaches into five groups which he called races and to which he gave the names: Persian, Northern Chinese, Spanish, Southern Chinese and Peento. He bounded peach-culture in America on the north by the Great Lakes and on the south by the Gulf and divided this great region into five zones to each of which he assigned one of his races. Onderdonk studied peaches in Texas and found there remarkable distinguishing characters; as, in adaptations to southern climates, in length of the rest-period, in differences in leafing, blooming and fruiting-time, and in the organs of the plants. Professor R. H. Price, working with a large number of varieties at the Texas Agricultural College, verified and greatly extended Onderdonk's observations.[187] Eventually, Price became the pontifical authority in this country on the classification of peaches and in numerous articles and addresses set forth the Onderdonk grouping of varieties so convincingly that it was adopted by practically all American pomologists and at present is in use, to some degree at least, in nearly all of our horticultural literature. It becomes necessary, therefore, to scrutinize closely this natural classification of Onderdonk and Price.

The end to be attained in a classification of peaches, as in classifying natural objects of any kind, is to provide an epitome of the knowledge of the fruits classified. Incidentally, a classification helps in the identification of varieties of peaches. Does the Onderdonk classification serve these purposes? We have not found that it does. In most arduous attempts to arrange the sorts of peaches growing on the Station grounds according to the Onderdonk plan, we have wholly failed. Even the varieties named as types do not fit, as they grow in the north, in the places provided for them by these southern classifiers. Indeed, we have wasted so much time and patience in attempting to group varieties according to Onderdonk and Price, and with so little success, that the Onderdonk classification seems to us to be cursed with the confusion of Babel. Since pomologists so generally accept this classification, these words demand that it be shown wherein this attempt at a natural arrangement of varieties fails.

In the first place the basis of Onderdonk's classification, as the names suggest, is regional variation. Each race stands for a region, the Peento included--for the name is very obviously Chinese. Incompleteness, then, is the first fault of this system for there are other regions in which races of peaches just as distinct as those named have developed: as, for examples, the Bokhara represents a hardy "Russian race;" Yellow Transvaal belongs to the very peculiar "South African race;" in the rich alluvial lands of Egypt, the "Egyptian race" has developed; still another regional race is found in the evergreen peach of the West Indies. We have no doubt that distinct races of peaches may have originated or will arise in the Canary Islands, Hawaii, New Zealand, Argentina, Chili and Mexico, to mention only countries spoken of in the foregoing pages. The Onderdonk classification can, of course, be extended to take in these new races, most of which are now represented in America, but eventually such a classification would become too cumbersome for use. It must not be overlooked that the Onderdonk classification should be doubled to apply to the nectarine, the other division of _Prunus persica_, which the present classification wholly ignores.

If the variations are stable, and all regions represented, the likenesses and differences brought about by regional environment may well be used by classifiers. But in the Onderdonk classification unstable variations due to climate are too largely used; as, differences in the succession of life-events, in the rest-period, in the capacity to endure heat and drought, and in minor modifications of organs, as color of foliage and shape of fruit. All of these are variations that fluctuate with even slight changes in the climate. We have said that this classification, though constantly referred to by northern fruit-growers, is not satisfactory in New York. Professor Price, too, found as he went northward that his classificatory scheme was less dependable. He says:[188] "Some of the distinctions made in this classification cannot be noticed with decisive clearness a few hundred miles farther north." A further objection to this regional classification of Onderdonk is that, in the numerous distinct peach-regions of America, new regional variations are arising which make it impossible to classify in accordance with characters that appeared before the peach came to America.

These "races" of Onderdonk and Price, then, by leaving out the peach-floras of many regions, are too exclusive, but it is no less true that they are too inclusive. Thus, the many varieties of the historic peach of western countries are put by the Onderdonk classification in the Persian race. So considered, this Persian race contains types quite as widely separated from each other as are the five "races" of the Onderdonk classification. In one great group are collected early, late, white-fleshed, yellow-fleshed, red-fleshed, globular, oblong, beaked, hardy and tender, vigorous and dwarfish peaches. Persian peaches run the whole gamut of peach-characters, the flatness of the Peento possibly excepted, and from the several hundred sorts a score of "races" might be made. These peaches are noted by Price and Onderdonk as requiring a long period of rest and as succeeding only in northern climates. Yet to this group belong the peaches of France, Spain and Italy; those of the warm parts of Africa, South America and Oceanica; and most of the varieties that thrive at the most northern limits of peach-growing in Europe and America.

The Onderdonk classification, in assigning zones to each of its five races, misleads peach-growers as to the hardiness of varieties. It makes the Peento and honey-flavored peaches much more tender in tree than they are. Varieties of both groups grow as far north as this Station and Waugh reports that one of the Peento varieties "was discovered growing thriftily and fruiting nicely on the grounds of the Massachusetts Agricultural College, Amherst, Massachusetts."[189] Of the score of descendants of the Honey, several are fruiting well on our grounds, four being illustrated and described in _The Peaches of New York_. If there were a demand for honey-flavored peaches, climate would not prevent their culture in New York.

The name used for the Peento group, if it be worth while keeping these peaches in a group, is inapt. It gives the impression that all, like Peento, are flat peaches--in fact Price several times so publishes them--whereas of the twenty-three sorts described by Hume,[190] though nearly all are seedlings of Peento, only Peento is flat. We must look upon the Peento as a peach-monster similar to the cleft peach, _Emperor of Russia_, the nippled peach, _Teton de Venus_, the _Perseque_ with its teat-like protuberances, or the more familiar snow-white and blood-red varieties.

We are not able to see where the Peento group leaves off and the Honey group begins in the Onderdonk classification, though, since varieties of the Peentos have not fruited at Geneva and the several Honey-flavored peaches, though both thrifty in tree and fruitful, are possibly not typical, we ought not to be too critical. As we read the descriptions made by others, however, we are struck by the fact that there are more similarities than differences in the two groups and that the differences are rapidly disappearing through hybridization.

But the obstacle which most effectually blocks the use of Onderdonk's classification in the systematic arrangement of peaches is the brood of hybrid seedling peaches annually brought forth by fruit-growers. No doubt the classification is workable, to a degree, with the type-varieties and a few carefully selected progeny but after the practical peach-grower, with a devil-may-care attitude toward classification, crosses and recrosses the types, the several races become hopelessly interlocked. The characters chiefly used by Onderdonk, as has been said, are fluctuating variations and these do not descend according to Mendelian laws. And so the great out-pouring of varieties during the past quarter-century has literally swamped a classification which served only fairly well when it included but the pioneer varieties. In the trituration of the thousand and more varieties of peaches now going on, the Onderdonk classification will be less and less useful.

In dismissing the Onderdonk scheme as having but limited application for classificatory purposes, acknowledgment is made that it serves other purposes very well. It calls attention to the history of the peach; it shows that racial strains of the peach are arising; it brings out valuable information in regard to hardiness and the rest-period of peaches; it offers instances of modification of the peach by climate; and it shows the capacity of the peach to vary. For thus illuminating the natural history of the peach, more especially the climatology of the peach, pomology is much indebted to Onderdonk and Price.

_A key to varieties of peaches._--A natural classification of peaches to show the relationships of varieties is seemingly impossible. The deluge of new varieties, which growers continue with cheerful optimism to pour out, overwhelms the classifier with difficulties. About the best that can be done is to arrange varieties, for convenience in identifying, according to some of the artificial systems of a century ago when the cult of the classifier was at its height. These were really synoptical keys rather than biological classifications. If such a key is to be used very generally by fruit-growers, only characters of the fruit are admissible, thereby attaining necessary simplicity and providing that all data can be had at one examination.

The first division of a synoptical key would of course be founded on the absence or presence of pubescence on the skin; these two great divisions would then be separated into freestones and clingstones; these, in turn, divided in accordance to color of flesh--white, yellow, red; the Peento and honey-flavored peaches make necessary a division in regard to shape--globular, flat, beaked; a further separation into early, medium and late sorts could then be made. A great merit in this extremely simple classification is that the language of the layman fits it. As examples: Greensboro would follow the key from bottom to top--an early, round, white-fleshed, freestone peach; or Salwey, a late, round, yellow-fleshed, freestone peach. This key provides for seventy-two groups, fifty-four for the peach and eighteen for the nectarine, the latter having but the globular form. Other characters, of less general application in the key than those so far used, as size, flavor, adherence or non-adherence of the skin, suture, apex, and stone, could be used to carry this classification still further.