But grafting in the fall in the open ground is unnecessary, where small seedling stocks are used in the propagation of any kind of tree; in fact, nurserymen do very little grafting of this kind in spring, for they learned, by long experience, that the most economical and certain method of multiplying such trees is to take up the stocks in the fall, and then graft them indoors during the winter, having stocks and cions stored in cool cellars or pits, where they will be readily accessible when wanted. Apples, pears, quinces, grapes, and many other kinds of hardy trees, shrubs and vines are now extensively propagated by grafting during the winter months, and I do not know of any good reason why the hickories and other closely allied nut trees should not be multiplied in this way. I have tried it, on a limited scale, with the shellbark hickories, and with fair success, and in my opinion it is the only way by which the hickories, including the pecan, can be multiplied cheaply enough to become of commercial importance.
The small stocks of one or two years old should be taken up in the fall, and then crown grafted any time from December to March in the Northern States, but the earlier the better; then pack away the grafted stocks in moss or soil, in a cool cellar, or heel-in elsewhere, as, for instance, in pits or frames, where they will not be frozen, and yet cool enough to prevent active growth.
In the spring the grafted stocks should be planted out in nursery rows, and deep enough to have the top of the cion just level with the surface after the soil has been settled about it by a shower or heavy rains. The plants must be handled with care, so as not to disturb the cions. Mulching will, of course, be beneficial in dry seasons, and especially if the stocks are set in ordinary well-drained soils. In selecting wood for cions, twigs of the previous season's growth are usually preferred, but it is not necessary, nor is it advisable to discard all except the extreme end of the shoot or that containing a terminal bud, as some writers have advised, to prevent rapid loss of moisture by evaporation, for a drop of wax will seal the end of a cion as thoroughly and effectually as a natural bud; besides, the lower part of the annual twigs is often more firm and really better for grafting than the upper and less sturdy wood, and the lateral buds on it will push just as readily as the terminal one. The cion may be three or four inches long, and contain two or more buds. The sealing of the upper end of a cion that is not protected by a terminal bud is certainly important with all of the hickories, for in this genus of trees the pith is large and continuous, not intersected or cut off by a thin partition of wood at the joints, as seen in many trees, shrubs and vines. This large and continuous pith in the hickories is another reason why the cions succeed best if set below the crown and in or on the fleshy roots having no pith. They may be set on one side, as in splice grafting, or in the center, or in a cleft made for their reception with a sharp knife, then bound with waxed paper, or wrapped with bass, raffia, or other similar material, and afterwards covered with melted wax to exclude air and water from the joints and wounds.
In this mode of grafting hickories it is not necessary to employ the entire root or stock, if it is of large size, for a single cion; for pieces of from six to twelve inches long, containing a few lateral fibers, will answer the purpose, and it will be found, in practice, that these sections of the large fleshy roots contain so much vitality that, if the cions set in them fail to grow, they will throw up sprouts from adventitious buds during the ensuing summer. Almost any fair-sized piece of root left in the ground, when digging up hickory trees large or small, is pretty certain to throw up sprouts, this not only showing their great vitality, but that propagation by root cuttings is perfectly practicable and may be utilized whenever and wherever it may be desirable. The man who attempts to raise hickories from root cuttings must have patience, for very frequently the cuttings will remain apparently dormant in the ground one entire season before the sprouts appear above the surface. I will also add that this slow or retarded germination frequently occurs with the nuts, especially if they have become somewhat dry before planting.
For commercial purposes root-grafting small stock, as described, during the fall and winter, gives promise of being the best and most practicable system of multiplying varieties; but there is much yet to be learned in regard to details, and hundreds of carefully conducted experiments may be necessary to determine the exact time, condition and mode of operation. It may be that very early grafting is better than late, or that we have not, as yet, found the best species for stocks, and that a half-ripened one will be preferable to one fully matured. Neither has it, as yet, been determined what kind of material is best in which to store the grafted roots: sand, soil or sphagnum (moss) from the swamps; or whether they should be kept very moist, or comparatively dry; very cold, or moderately warm. Here is a wide field for experiments, and a most interesting one; for the successful propagation of the hickories by any mode that will insure the perpetuation and rapid multiplication of varieties, means millions of dollars added to the wealth of the country.
Age of Fruiting.—We hear much of the precociousness of pecan trees in the South, and many are reported as coming into bearing at the age of six to ten years from the time of planting the nut; but these are probably exceptional instances of early fruiting and not the rule, although in a favorable soil and climate it is to be expected that such trees will push forward more rapidly than under less favorable conditions. Grafted trees will, of course, produce fruit in less time than seedlings, and as this mode of propagation becomes more general, and repeated in a direct ancestral line, the cions for each successive generation of trees being taken from mature or bearing specimens, the precocious and productive habit will eventually become intensified, as it has been in all of our long-cultivated fruit trees propagated by artificial methods. We have so intensified the productiveness of many kinds of cultivated fruits by selection, that it has become more of a fault, than a merit to be encouraged.
The nut trees are amenable to the same physiological laws as other kinds, and in their propagation by grafting with cions from bearing specimens we hasten maturity in the offspring. This has been fully demonstrated in many varieties of the Persian walnuts and European chestnuts. Here in the Northern States we have had so little experience with grafted hickories of any species, that really nothing is yet known as to how they will respond to this mode of propagation, further than that they grow rapidly and give promise of being fruitful. Seedling trees are, as a rule, of slow growth, rarely attaining a bearing age and size under twenty years, and with the shellbarks thirty or forty years usually pass before anything like a crop of nuts is gathered. Something may be gained, in the way of time, by frequent transplantings and pruning, but more by grafting seedlings from old and mature trees. Two grafts of the Hales' hickory commenced bearing at the age of sixteen years.
Planting for Profit.—There are, doubtless, many thousands of acres of half-denuded woodlands in almost every State in the Union, both North and South, that could be readily utilized for growing hickory timber, and much of such lands is almost useless for other purposes; but timber culture and forestry is a subject which I have discussed elsewhere,[1] while the object of this work is to aid my readers in producing something that may be utilized as food. When the hundreds and thousands of miles of our public highways are shaded with hickory and other nut-bearing trees of the best species and varieties, it will be time enough to begin planting such kinds elsewhere. As roadside trees they cannot fail to be profitable, largely enhancing the value of adjoining land; for in addition to being equally as ornamental as other kinds, they yield fruit always in demand at remunerative prices. The three species of the hickory and their varieties recommended for cultivation all thrive best in moist soils, but by occasional watering or thorough mulching they will succeed almost anywhere, especially in naturally dry locations.
[1] Practical Forestry.
Insect Enemies.—The hickories, as with all other nut-bearing trees, have numerous insect enemies, but these are neither so numerous nor destructive as to seriously interfere with their growth in general, or with their productiveness. Insects may occasionally become exceedingly numerous in certain localities for a few years, then suddenly or slowly disappear; but this we must expect, as one of the coexisting phases of all agricultural pursuits.