The grafting of plants
This section from Manual of Gardening, by L. H. Bailey
Grafting is the operation of inserting a piece of a plant into another plant with the intention that it shall grow. It differs from the making of cuttings in the fact that the severed part grows in another plant rather than in the soil.
There are two general kinds of grafting--one of which inserts a piece of branch in the stock (grafting proper), and one which inserts only a bud with little or no wood attached (budding). In both cases the success of the operation depends on the growing together of the cambium of the scion (or cutting) and that of the stock. The cambium is the new and growing tissue lying underneath the bark and on the outside of the growing wood. Therefore, the line of demarcation between the bark and the wood should coincide when the scion and stock are joined.
The plant on which the severed piece is set is called the stock. The part which is removed and set into the stock is called a scion if it is a piece of a branch, or a "bud" if it is only a single bud with a bit of tissue attached.
The greater part of grafting and budding is performed when the scion or bud is nearly or quite dormant. That is, grafting is usually done late in winter and early in spring, and budding may be performed then, or late in summer, when the buds have nearly or quite matured.
The chief object of grafting is to perpetuate a kind of plant which will not reproduce itself from seed, or of which seed is very difficult to obtain. Scions or buds are therefore taken from this plant and set into whatever kind of plant is obtainable on which they will grow. Thus, if one wants to propagate the Baldwin apple, he does not for that purpose sow seeds thereof, but takes scions or buds from a Baldwin tree and grafts them into some other apple tree. The stocks are usually obtained from seeds. In the case of the apple, young plants are raised from seeds which are secured mostly from cider factories, without reference to the variety from which they came. When the seedlings have grown to a certain age, they are budded or grafted, the grafted part making the entire top of the tree; and the top bears fruit like that of the tree from which the scions were taken.
There are many ways in which the union between scion and stock is made. Budding may be first discussed. It consists in inserting a bud underneath the bark of the stock, and the commonest practice is that which is shown in the illustrations. Budding is mostly performed in July, August, and early September, when the bark is still loose or in condition to peel. Twigs are cut from the tree which it is desired to propagate, and the buds are cut off with a sharp knife, a shield-shaped bit of bark (with possibly a little wood) being left with them. The bud is then shoved into a slit made in the stock, and it is held in place by tying with a soft strand. In two or three weeks the bud will have "stuck" (that is, it will have grown fast to the stock), and the strand is cut to prevent its strangling the stock. Ordinarily the bud does not grow until the following spring, at which time the entire stock or branch in which the bud is inserted is cut off an inch above the bud; and the bud thereby receives all the energy of the stock. Budding is the commonest grafting operation in nurseries. Seeds of peaches may be sown in spring, and the plants which result will be ready for budding that same August. The following spring, or a year from the planting of the seed, the stock is cut off just above the bud (which is inserted near the ground), and in the fall of that year the tree is ready for sale; that is, the top is one season old and the root is two seasons old, but in the trade it is known as a one-year-old tree. In the South, the peach stock may be budded in June or early July of the year in which the seed is planted, and the bud grows into a saleable tree the same year: this is known as June budding. In apples and pears the stock is usually two years old before it is budded, and the tree is not sold until the top has grown two or three years. Budding may be performed also in the spring, in which case the bud will grow the same season. Budding is always done on young growths, preferably on those not more than one year old.
Grafting is the insertion of a small branch (or scion), usually bearing more than one bud. If grafting is employed on small stocks, it is customary to employ the whip-graft. Both stock and scion are cut across diagonally, and a split made in each, so that one fits into the other. The graft is tied securely with a string, and then, if it is above ground, it is also waxed carefully. SCION: a bud or shoot taken from one plant and grafted on to another(the ROOTSTOCK). See pages 52-53 from 'THE PRINCIPLES OF GARDENING' by HUGH JOHNSON, Simon and Schuster, 1979.
In larger limbs or stocks, the common method is to employ the cleft-graft. This consists in cutting off the stock, splitting it, and inserting a wedge-shaped scion in one or both sides of the split, taking care that the cambium layer of the scion matches that of the stock. The exposed surfaces are then securely covered with wax.
Grafting is usually performed early in the spring, just before the buds swell. The scions should have been cut before this time, when they were perfectly dormant. Scions may be stored in sand in the cellar or in the ice-house, or they may be buried in the field. The object is to keep them fresh and dormant until they are wanted.
If it is desired to change the top of an old plum, apple, or pear tree to some other variety, it is usually accomplished by means of the cleft-graft. If the tree is very young, budding or whip-grafting may be employed. On an old top the scions should begin to bear when three to four years old. All the main limbs should be grafted. It is important to keep down the suckers or watersprouts from around the grafts, and part of the remaining top should be cut away each year until the top is entirely changed over (which will result in two to four years).
|Standard Cyclopedia of Horticulture|
Grafting, Multiplication by. Grafting is the operation of inserting a part of one plant into another plant or part with the intention that it shall grow and produce its kind.
The practice of grafting, together with all the reasons, consequences and results, constitutes a department of knowledge known as graftage. The term grafting is ordinarily restricted, in popular speech, to propagation by means of short twigs or scions, and budding is used to designate the insertion of single buds that arc severed from the branch on which they grew; but these distinctions are not fundamental. Stock is the plant or part on which the grafting is done. Scion (cion, sion) is the part inserted into the stock, although it is usually restricted to cuttings of twigs, and does not include detached buds. In many writings the word is spelled scion, but the other is shorter and it was a very early horticultural term, many old horticultural writings using don and cyan. Scion is apparently later, and usage is not uniform. The word graft is sometimes used in the sense of don, but it would better be used for the completed thing — the new plant or part made by the joining of scion and stock.
Grafting is not always employed for purposes of propagation. It may be a reparative process. What is known as bridge-grafting is of this kind. Wounds or girdles may be bridged by scions, as in Fig. 1672 (after Hedrick), for the purpose of supplying new tissue to connect the parts. Here the edges of the girdle are trimmed to the fresh firm tissue, scions whittled wedge- shape at each end are inserted, bandages are drawn around the trunk to hold the free edges of the bark and the ends of the scions, and wax is poured over the work. This operation is performed in spring, with dormant scions. The buds should not be allowed to throw out shoots. If the scions are placed close together, they will soon unite along their sides and make a continuous covering of the wound. Writing of bridge-grafting, Hedrick says (N. Y. Sta. Circ. No. 17): "Its most important use is to preserve trees injured or girdled by rodents or disease. Any ragged or diseased edges should be cleanly cut away, a longitudinal slit should be made in the bark, both above and below the wound, and the edges of the slits loosened slightly. A scion should then be cut 2 or 3 inches longer than the space to be bridged, one side beveled off at both ends (Fig. 1672), and inserted in the slits, its beveled face against the wood of the trunk. In order to guard against any accidental displacement it would be well to drive a small tack or nail through each end of the scion, which, however, must not be split in the operation. Other scions in a like manner may be inserted at intervals of about 2 inches over the entire injured surface. The ends of the scions should be covered with wax but it is not necessary to cover all the bridged portion of the trunk. If the tree operated upon is small and likely to weave in the wind it should be tied firmly to a strong stake as such movements might tear apart the tender uniting surfaces."
Cions are sometimes inserted freely in the stub left by a large broken limb, for the double purpose of providing other shoots to take the place of the branch and of facilitating the healing of the wound. Sometimes scions are inserted in limbs on a one-sided or misshapen tree for the purpose of securing better growth on that side, the variety perhaps being the same as that of the tree itself.
Another reason for grafting is to produce some radical change in the nature of the scion, as rendering it more dwarf, more fruitful, or otherwise changing its habit. Still another office is to adapt plants to adverse soils or climates. An example is the use of the peach root in the southern states upon which to work the plum, as the peach thrives better than the plum in sandy soils. The practice in Russia of working the apple on roots of the Siberian crab is an example of an effort to make a plant better able to withstand a very severe climate.
In general, however, grafting is employed for the purpose of multiplying or perpetuating a given variety, mostly of woody plants. It is used with plants that do not bear seeds, or in which the seeds do not come true or are difficult to germinate, or when the plants do not propagate well by cuttings or layers. It is also employed to increase the ease and speed of multiplying plants.
In common practice, the effect of the stock on the scion is rather more mechanical or physical than physiological or chemical. The influences are very largely those associated with greater or less growth. As a rule, each part of the combined plant—-the stock and scion—smaintains its individuality. There are certain cases, however, in which the scion seems to partake of the nature of the stock; and others in which the stock partakes of the nature of the scion. There are recorded instances of a distinct change in the flavor of fruit when the scion is put upon stock that bears fruit of very different character. There are some varieties of apples and pears which, when worked on a seedling root, tend to change the habit of growth of that root. Examples are Northern Spy and Whitney apples, which, when grafted on a root of unknown parentage, tend to make that root grow very deep in the soil. All these instances seem to be special cases, or exceptions to the general rule that each part maintains its individuality. Reasons for this change of nature in these cases have not been determined, and in most cases such results are not to be predicted. The most marked effect of stock on the scion is a dwarfing influence. Dwarfing may be expected whenever the stock is of a smaller stature than the scion. The most familiar example is the dwarf pear, made by working the pear on quince stock. Supplying a plant with a slow-growing root is only the beginning of the making of a dwarf. The plant must be kept dwarf by subsequent pruning and other care. There is comparatively little demand for large-growing forms of woody plants, whereas there is much demand for dwarf forms. See Dwarfing, page 1082.
The limits within which grafting can succeed are to be determined only by experiment. These limits are often within the species, and usually within the genus, but there are instances in which plants of distinct genera intergraft with success, as in some of the cacti. In general, the closer the affinity of scion and stock, the better the union. When stock of the same species cannot be secured, it is allowable to chose another species. Thus it was for a time impossible to secure Japanese plum stocks upon which to grow the varieties of Japanese plums, and peach, Marianna, myrobalan and domestica plum stocks have been used, and are used to this day. In some cases another species grows more readily from seed, is cheaper, is less liable to fungous injury in the nursery, or has some other practical advantage. Thus, most domestica plums (Prunus domestica) in the North are worked on the myrobalan (P. cerasifera); many sweet and sour cherries (Primus avium and P. Cerasus) are worked on the mahaleb (P. Mahaleb); many kinds of roses are worked on mahctti and Rosa multiflora stocks.
From time to time there arises an agitation against grafting, particularly in the Old World. Cases of poor unions and the difficulties of sprouting from the root or stock are cited as proofs that graftage is injurious and devitalizing. But these are examples of poor results. They show what should not be done. Properly performed, on plants of proper affinity, graftage is not devitalizing. It is essential to modern horticulture.
The ways or fashions of grafting are legion. There are as many ways as there are ways of whittling. The operator may fashion the union of the stock and the scion to suit himself; if only he apply cambium to cambium, make a close joint, and properly protect the work. Thus, Thouin in his "Monographic des Greffes," 1821, ' describes 119 kinds of grafting. All kinds of grafting may be classified into three groups:
1. Bud-grafting or budding. In the old days called inoculation.
2. Scion-Grafting, or what is now thought of as grafting proper.
3. Grafting by approach, sometimes called inarching.
Grafting is one of the oldest of the arts of plant-craft. It is probable that the real art of grafting was held more or less as a professional or class secret in the ancient world, for the writers seem to have only the vaguest notion of its possibilities and limitations. Virgil writes (Preston's translation):
But thou shalt lend Grafts of rude arbute unto the walnut tree, Shalt bid the1 unfruitful plane sound apples bear. Chestnuts the beech, the ash blow white with the pear. And, under the elm, the sow on acorns fare.
It seems to have been a popular misconception that any kind of plant will grow on any other. Pliny .asserts that the art of grafting was taught to man by nature. Birds swallow seeds, and these seeds, falling in "some cleft in the bark of a tree," germinate and make plants. "Hence it is that we see the cherry growing upon the willow, the plane upon the laurel, the laurel upon the cherry, and fruits of various tints and hues all springing from the same tree at once." This, of course, is not grafting at all, but the implanting of seeds in earth- filled chinks and cracks, in which the plants find a congenial foothold and soil. But the ancients have left us abundant testimony that genuine grafting was employed with success. Pliny describes a cleft-graft. He gives several precautions: the stock must be "that of a tree suitable for the purpose," and the graft must be "taken from one that is proper for grafting; the incision or cleft must not be made in a knot; the graft must be from a tree "that is a good bearer, and from a young shoot;" the graft must not be sharpened or pointed "while the wind is blowing;" "a graft should not be used that is too full of sap, no, by Hercules! no more than one that is dry and parched;" "it is a point most religiously observed, to insert the graft during the moon's increase."
Herein are seen the beginnings of the grafting practices of the present day, together with some practices of layering. Sharrock treated the whole subject of grafting under the head of "Insitions," and here he minutely describes the cleft-graft, and speaks of it as "the common way of grafting." The practice which we now know as inarching or grafting by approach, he significantly calls "Ablactation" (that is, suckling or weaning). Now that so much is said about the proper and careful selection of scions, it is interesting to read Shar- rock's advice on this subject: "Good bearing trees are made from Cyons of the like fruitfulness. . . . Cyons are best chosen from the fairest, strongest shuits, not from under shoots or suckers, which will be long ere they bear fruit, which is contrary to the intention of grafting." But we have seen that Pliny gave similar advice before the Christian era,—which is only another illustration of the fact that most of our current notions have their roots deep in the past.
The accompanying cut (Fig. 1673) reproduced two- thirds size from Robert Sharrock's "History of the Propagation and Improvement of Vegetables," 1672, shows various kinds of grafting in vogue over two centuries ago.
The operation of budding consists of inserting a single detached bud underneath the bark of the stock. It is employed only in stocks of small diameter, and preferably in those not more than one year old. The operation may be performed whenever the bark will peel and whenever mature buds may be secured. The bark will peel in early spring and again in late summer or early autumn, and the operation of budding in the open ground is therefore performed at those times. In the spring the buds are secured from twigs of the previous season's growth. At the second budding season, in late summer or early autumn, the buds are secured from growing twigs of the season. At that time of the year the buds will be sufficiently developed to be easily recognized and handled.
Budding is much employed in nurseries. Peaches, cherries, plums, and most stone fruits, are habitually budded rather than scion-grafted. In the East, apples and pears are usually budded in the nursery; but in the West apples at least are usually root-grafted. Third-rate stocks are sometimes set in nursery rows and budded the following July.
It is practicable to insert buds rather than scions in the tops of young trees, for the purpose of changing the tree into a different variety. Sometimes the buds are inserted in limbs two and three years old; but it is usually preferable, if the tree is of some age, to cut back the tree somewhat heavily the previous season or the previous spring, to get a growth of suckers into which the buds may be set.
The cutting from which the buds are taken is known to budders as a stick (Fig. 1674). In early spring-budding, this stick is the last year's growth of the variety which it is desired to propagate. Later in the season, the stick is the twig grown in that season. Not all the buds on the stick are strong enough or good enough for budding. The budder will usually discard the weak ones at the top and at the bottom, unless he is very much pressed for buds, as may be the case with new or rare varieties. If the stick is taken late in the season the leaves will be on; but these are quickly cut off to prevent too much evaporation from the cutting. About ¼ inch of the leaf-stalk is left to serve as a handle to the bud.
The ordinary operation of budding is shown in the illustrations. It is known as shield-budding, from the shape of the removed bud. With a thin-bladed, sharp knife, the operator slices off the bud by placing his thumb beneath the bud and making a deft and quick stroke of the blade. Just under the bud he cuts a little into the wood. Some budders afterward remove this bit of wood; but this is not essential. If this wood is somewhat hard stick of and dry, or if it carries some pith, it may then buds, serve to dry out the bud or to prevent intimate contact with the cambium of the stock. In ordinary operations this truncheon of wood is not removed. Most budders cut all the buds on a stick before they insert any of them; but they are allowed to hang to the stick by their upper ends, being snipped off by the knife as fast as they are needed (Fig. 1674).
Wester writes as follows on the requirements in budding citrus fruits (Bull. No. 27, Bur. Agric., Philippine Isls.), and the directions will apply to other plants; and he gives pictures (Figs. 1675, 1676) of part of the manual operation: "Many people are under the impression that budding is a very complicated operation, correspondingly difficult to learn and to perform. As a matter of fact this is not true. Some judgment must of course be exercised in all phases of the work, but the art of budding itself is a mere matter of manual skill that anyone should be able to master who is at all deft in the handling of a knife. Necessary essentials for success are: (1) Stock plants in condition for budding; i.e., the flow of sap must be good so that the bark separates readily from the wood. (2) A suitable budding-knife, the edge of which should be sharp and keen as a razor, and clean of all impurities; an ordinary pocket-knife will hardly answer the purpose. (3) Proper bud-wood; immature bud- wood will not 'take' and the proper cutting of buds from old and hard bud - wood is difficult. (4) The bud-wood should never be allowed to dry out by being exposed to the air or sun. (5) The buds should be inserted immediately after being cut and the bud tied at once. (6) No foreign matter or water should be allowed to enter the bud incision. (7) The bud should be cut so that there is no break or tear in its tissues."
The stock is first prepared by removing all the leaves and twigs from the area to be budded. In the case of nursery stock, it is customary for a boy to strip the lower leaves of the stock a day or so in advance of the budding. If the stripping is done three or four days or a week before the budding, it will sometimes cause the bark to set and, therefore, interfere with the operation. Nursery trees are usually budded as near the ground as the operator can work—not more than 2 or 3 inches above the surface. In most cases, the budder prefers to set the bud on the north side of the stock, that it may be shaded from the hot sun.
A T-shaped incision, just through the bark, is made on the stock (Fig. 1677). The crosswise incision is usually made first. As the operator takes his knife from the last incision, he gives it a deft turn to right and left and loosens the flaps of the bark, so that the bud is easily inserted. The bud is now taken from the stick and shoved into the matrix underneath the bark until it is entirely within the cleft (Fig. 1678). A boy follows and ties the bud, making four or five deft turns and holding the strand by covering the lower end underneath one of the turns (Fig. 1679). No wax or other mastic is used. Any soft strand may be employed for the tying. It was the old custom to use basswood bark, which was taken in the spring from the inner layers of the bark of the basswood tree. This material was then macerated in water and afterward pounded to make it soft. Yarn is also used. At present, raffia is universally employed. This is the stripping of an oriental palm, and it can be bought in the market and is cheaper than home-made materials; it is also better. It is customary to lay it on the ground or in a damp place over night to soften it and to allow the operator to flatten out the strands. This raffia is cut in the length to suit before the tying is begun, and the bunch of strands is then held underneath the belt or carried in a box. For budding, the operator prefers a small, thin-bladed knife, with a rounded or thumb- shaped cutting surface (Fig. 1680). Budding knives are regularly on the market.
When budding is performed late in the season, the bud does not throw out a shoot until the following spring. It merely grows fast or "sticks" to the stock. Two or three weeks after the setting of the bud, the bandage is cut so that it will not restrict the swelling of the stock. If the stock grows very rapidly, it may be necessary to cut the bandage before that time. Nothing more is done with the tree until the following spring, at which time the whole tree is out off about 1 inch above the bud. This one bud now throws out a shoot and makes a very heavy growth, being impelled by the strong root. In this first season of growth, a peach tree will attain the height of 4 to 6 feet, and be ready for market in autumn. If the bud is set early in the spring it will throw out a shoot the same season; but ordinarily it would not make the growth in one season that the bud docs in the other case. Spring-budding in the open air is rarely employed in nursery practice. It is sometimes used in the top-budding of established plants. In all budding practices, it is important to keep down the suckers from the stock.
In the South, a peach tree may be large enough in June, if the seeds are planted in February or March, to be budded. The bud will grow the same year, and by autumn will make a salable tree. This operation of budding in early summer on stocks which grow that year is known as June-budding. As a rule,' June-budded trees are smaller than fall-budded trees; but they can be secured one year sooner.
Other forms of budding.
There are many ways of shaping the bud. These modes may have distinct advantage in certain plants, because of the way in which the bark holds its shape, of the relation to the drying out of the parts, and otherwise.
The rectangular-patch method is illustrated by Sharrock (d, g, To, Fig. 1673). It is recently described by Oliver as one of the successful methods of propagating the mango. (Bulletin No. 46, Bur. PI. Ind., II. S. Dept. Agric.): "The only departure from Sharrock's method of budding as used in the case of the mango at the present time is that the bud, instead of being taken from new growth, must be selected from wood old enough to have lost its foliage. This means that the bud-wood will sometimes be over two years old. The use of bark of this age and even older insures success in budding the mango, as it unites rapidly with bark of a similar age on seedling stocks or on branches of trees. To a certain extent success depends upon the precision with which the section of bark is removed from the stock and also from the variety to be propagated, as the more neatly the bud section is fitted into the space prepared for it the greater the probability of a successful union (Fig. 1681). After the section of bark from the bud stick is nicely fitted in place, and before tying, a small quantity of grafting- wax should be smeared over the parts where they come together and tied firmly in place with thick strands of raffia. This effectually prevents the admission of auto the spaces which, no matter how carefully the operation be performed, exist between stock and scion; it also serves to prevent moisture from gaining access to the cut surfaces. The cut surfaces and all but the bud should then be covered with strips of cloth dipped in melted paraffin, wrapping being begun at the lower part, so that when finished water will not gain entrance to the wrapped section of bark. If that part of the stock where the bud js tied be exposed to the sun, it is always advisable to furnish shade which is best supplied by strips of paper tied above the bud and extending down over it. Two weeks may be allowed to pass before an examination is made. The cloth wrappings may then be removed and the raffia should be loosened if there is danger of its cutting into the bark. When a sufficient time has elapsed to make certain that a union has taken place, part of the top of the stock should be removed in order to encourage the bud to start. This it will do with very little coaxing. When sufficient growth has been made, all of the stock above the bud may be removed and the cut part coated with liquid grafting-wax or tar to exclude moisture and prevent rotting." Fig. 1682 shows the successful growth of the patch-bud.
The spade-shaped bud, shown in Fig. 1683, has been employed with the mango and other plants. The pointed end makes it possible, according to Oliver, "to push the bark of the scion down tight against the bark of the stock; the top part is then cut off square with the transverse cut in the bark of the stock, and is pressed firmly into position previous to tying and waxing in the usual way." These two forms of budding are given here only for the purpose of illustrating interesting methods, and not necessarily to advise their use.
Improved methods of budding the pecan have been developed in Texas by Charles L. Edwards. He prefers spring-set buds, as they have the whole growing season before them and make salable trees by autumn. The summer-bud makes only a start before autumn, at best; most of them remain dormant till spring, and not a few dry out and perish. One method is shown in Figs. 1684, 1685. The stocks are cut off bodily, and straight across. A slit is then made in the bark at the top (A), and the bark opened to receive the bud. The buds are cut like shield- buds for peaches and plums (B, front and back views), but in addition, the bark is cut away from the lower end of the bud (C), reducing it to a point so it will slip into place easily (D). By the removing the thick rim of the bark from the lower end of the bud; the sap from the stock will enter it easily, and force it into immediate growth, whether put on in early spring or as late as September. At E the bud is shown in place, and the flaps pared. To put on the wrapper, use an oblong little square of waxed cloth with an eyelet in the middle for the bud to emerge from (F). In preparing the cloth for these wrappers, use only beeswax, not grafting-wax for this purpose. Be sure to tie on the wrappers firmly, and sec also that they cover the entire top of the stock, leaving no part of the wounds made by the knife uncovered. A modified shield-bud is used by Edwards. In Fig. 1686, the part marked A shows the outside and inside of the bud as commonly made for the pecan; B shows the thick rim of bark at the lower end. The modification consists in trimming away the lower end, as at C; also in paring away part of the flap, as at G. At E is the regular slit; F, the bark opened to receive bud; D, waxed wrapper; H, wrapper tied on. See Pecan.
Proper time to bud. (Hedrick.)
Inasmuch as the various kinds of trees used as stocks for budding vary greatly in length of their growing season, it naturally follows that the time during which they may be budded will vary accordingly. In a normal season, the figures for New York are about as follows:
Rose July 1 to July 10.
Pear July 10 to July 15.
Apple July 15 to August 1.
Plum (St. Julien stock) .July 15 to August 1.
Plum (Myrobalan stock) August loto September 1.
Cheriy (Mazzard stock) July 20 to August 1.
Cherry (Mahaleb stock) August 20 to September 1.
Quince July 25 to August 15.
Peach August 20 to September 10.
Grafting proper is the operation of inserting a twig or a woody scion into a stock. They may be classified in respect to the place or position of the scion on the stock:
Root-grafting, or the insertion of the scion in the root of the stock;
Crown-grafting, or the insertion of the scion at the crown (surface of the ground);
Stem-grafting, or the insertion of the scion in any part of the main stem or trunk;
Top-grafting, or the insertion of the scion in the top or branches of the plant.
Grafting may again be classified in respect to the maturity of the scion: dormant wood grafting; and softwood or herbaceous grafting, in which the scion is taken from green or growing wood.
It is customary to classify grafting on the way in which the union is made. There are few general types in common use in this country: as cleft-grafting, whip- grafting, veneer-grafting (side-grafting, bark-grafting).
Cleft-grafting consists in splitting the stock and inserting a wedge-shaped scion into the cleft. It is employed only in rather large stocks, preferably in those an inch or more in diameter. The stock is cut off, and it is split with a knife or tool made for the purpose. The cleft is then held open by a wedge and the scions are inserted in the side of the cleft in such position that the cambiums of the stock and scion are in contact (Fig. 1687). The whole surface is then securely waxed, to prevent evaporation and to protect the wounds from the sun (Fig. 1688). Cleft-grafting is> performed in early spring. The scions are taken some time previously from the last year's shoots. They are stored in a cellar or other cool place in order that they may be perfectly dormant. It is customary to cut them of three buds' length; but if the shoot is very long-jointed and if the variety is new or rare and the wood therefore scarce, they may be made of one or two buds. The wedge- shaped part should be somewhat thicker on the outside so that it may be clasped tightly in the cleft. (Fig. 1689). It is customary to have one bud near the top of the wedge. Although this bud is covered with wax, it is the most likely to grow, since it is nearest the source of food-supply and is less injured by external conditions. It pushes through the wax. It is customary to insert two scions in all stocks, even though only one branch is desired. By inserting two scions, the chances of success are doubled, and the wounds heal better if a twig grows on either side. After a year or two, one of the scions may be cut off if desired.
Cleft-grafting is the method usually employed in the top-grafting of fruit trees, as apples, pears, plums and cherries. Old peach trees are rarely changed over to a new variety. If they are, budding is employed, as already suggested: the limbs are headed back so that new wood is secured in which the buds may be set. It is important, in all top-working of fruit trees, to keep down the suckers which spring up around the scion, and which sometimes completely choke it. In changing over the top of a fruit tree, all the leading branches should be grafted (rig. 1690). It is well to stand at some distance from the tree and make a mental picture of how the tree will look when the new top is secured: the grafts should be set in approximately a radius from the center of the tree. It is rare that the stock should be larger than 2 inches in diameter where the scions are set. On some of the main branches it may be necessary to graft side branches lower down in order to fill the top and to afford footholds to pickers and pruners. It will require from three to four years to change over a tree in full bearing to a new variety. Each year a little more of the original top is removed, and the scions take more and more of the space.
Grafting-wax is of many kinds, but the most serviceable for applying with the hands in the open air is made by melting together one pound (by weight) of rendered tallow, two parts of beeswax and four parts of resin. The melted liquid is poured into a pail or tub of water, when it immediately hardens. It is then pulled until it is light-colored and develops a grain. It is then put away for future use, and will keep indefinitely. When the wax is used, the warmth of the hands will cause it to soften. The hands should be greased to prevent it from sticking.
For a softer wax, more tallow may be used; or linseed oil may be substituted, but because of adulteration of the oil the results are not always reliable.
Alcoholic waxes, or plastics, are sometimes made, to be applied with a brush or swab; on application, the alcohol disappears and the material hardens. A standard formula (Lefort's) is: best white resin, one pound; beef tallow, one ounce; melt, then remove from fire and add eight ounces alcohol. Keep in tightly closed bottles. .Sometimes a teaspoonful of turpentine is added.
Whip-grafting, or tongue-grafting, is employed in the nursery and on very small stocks. It is not used in top-grafting except now and then on small limbs. The scion and stock should be of approximately equal size. Each is cut off in a slanting direction, and a split or tongue is made near the middle. The same shape is given to scion and stock. The pictures sufficiently illustrate how the work is done. (Figs. 1691-1693). The object of the tongue is to hold the parts together securely; it also presents more cambium surface contact. The scion is then waxed, bound to the stock, preferably by means of waxed cord. If the graft is above ground, the wounds should be thoroughly waxed over the string. If the graft is below ground, the tie will be all that is necessary: the moist earth packed around the wound will prevent evaporation and protect it.
The chief use of the whip-graft is in root-grafting, which is employed largely on apples and mostly at the West. In the East, other things being equal, budded apple trees are preferred to root-grafted trees. In the West, however, it is necessary to have apple trees on roots of known hardiness. The seedling stocks are not of known hardiness, even though the seeds have come from the hardiest varieties. It is therefore customary to use scions 6 to 12 inches long, grafted on pieces of roots 2J4 to 4 inches long. (Fig. 1693.) The graft is set so deep that only the top bud of the scion projects above the surface. The piece of root acts as a nurse, and roots may start from the scion itself. (Fig. 1694.) When the tree is transferred to the orchard, the original root may be cut off in case it is not very vigorous; although this is not done if the union seems to be good and the foster roots are strong. This root-grafting is done in winter (December and January preferred); the grafts are stored in clean sawdust, sand or moss in a cool cellar, and are set in nursery rows in the open early in the spring, after the manner of grape-cuttings.
The waxed string, with which the whip-grafts are tied, may be made by dropping a ball of yarn into melted grafting-wax. In five minutes the wax will have penetrated the ball, but the strand can readily be unwound. The best material for this purpose is No. 18 knitting-cotton. This is strong enough to hold the work together, and yet weak enough so that it may be broken in the hands without cutting the fingers. It will ordinarily decay during the year, and thereby not interfere with the growth of the tree. If the grafting is performed in a room at a living temperature, the waxed string should be soft enough to stick to the stock without being tied. Four or five turns are made around the union. Waxed manilla paper, cut in narrow strips, is also used; also single strand cotton "chain" or warp-thread, either waxed or not waxed.
Any sharp knife with a handle large enough to be grasped readily is useful for whip-grafting. The blade should be thin, and the gteel of best quality. The handle should also be strong. Fig. 1695 shows a common form of grafting-knife. Good shoe-knives may be used. This and similar knives are in the market. A hone and whetstone should be near at hand, for the edge should be keen.
This style of grafting, which is considerably used under glass with fancy and ornamental plants, consists in simply champering the sufaces of scion and stock and applying the one to the other. (Fig. 1696.) The scion is bound to the stock by raffia or other material. If the graft is in the open, the wounds are thoroughly waxed; but in the house they may be covered merely with moss. This style of union is used with herbaceous plants, as well as on hard wood. Sometimes the stock is severed at the point of union, as in Fig. 1696; but in other eases it is not severed nor headed back until the scion has taken hold (Fig. 1697). In the latter case, the stock is not injured in case the graft does not grow.
Writing of the propagation of the tea plant under glass (which is suggestive for other plants in houses), Oliver says: "Seedling stocks may be grown in 4- or 5-inch pots for the reception of scions by the veneer method of grafting. To have the plants in perfect condition for working, it is necessary that they be grown from the seedling stage without a check, as the healthier the plant the better the chance of a successful union. Another important matter in this connection is that the stock plants should not be allowed to form matted roots in small pots; therefore, it will be found better to lift them from the nursery and put them in pots previous to the operation: or they may be gro%vn and (grafted while in garden flats. If this last-named method is chosen the plants should be situated far enough apart in the flats to be easily handled. If the grafting is performed while the stocks are in active growth, the union will take place more quickly than when the plants are in a dormant condition. The operation should be performed in the early part of spring. Fig. 1698 shows how the incision in the stem should be prepared. This should be made with a sharp knife and the cut at the deepest part should not be more than one- third of the diameter of the stem. The scion must be shaped at the base so that it will fit neatly into the place prepared for it on the stock. It should then be tied, and afterward a small quantity of sphagnum moss should be tied over the part where the stock and scion come together. Immediately after the operation is performed as above described, the plants should be placed in a close shaded propagating-frame and kept there until the union is effected; this will take place in a few weeks. The temperature of the frame should then be kept uniformly at 60° to 65° F. If a layer of sphagnum moss be put under the pots and the contents of the frame syringed occasionally a favorably humid atmosphere will result. Where greenhouse accommodations are not available for the propagating-frame a hotbed may be built out-of-doors in a location where the sun will not have much effect in raising the temperature. From 6 to 9 inches of stable litter and leaves will provide ample heat during the spring. When it is found that the scions have made connection with the stocks, air should gradually be admitted to the frames. Shortly after this the tops of the stocks may be cut off close to the scions. Planting out may be deferred till the scions have made their first growth."
A form of veneer graft is what is sometimes called the side-graft. It is shown in Fig. 1699 (adapted from Oliver).
When a woody scion is inserted underneath the bark in the side of the stock, as a shield-bud is inserted, the method is sometimes known as scion-budding. In describing a simple way of propagating the fig, Oliver writes: "This method consists of preparing the stock for the reception of the scion as in shield-budding. This is done by making a transverse cut through the bark ¾ inch in length. From the middle of this incision another cut is made toward the main stem or root for fully an inch. The bark is then pried up as seen in Fig. 1700. Instead of inserting a single shield-bud, a small twig having one terminal and one or two lateral buds is used. The scion is prepared as follows: A long scarf is made at one side through the pith and a thin piece of the bark on the reverse side is removed. With the long cut facing the stock the scion is pushed deeply into the place prepared for it, and is tied firmly with raffia. The corners of the bark of the stock are brought close to its own stem and bound firmly in that position. Melted grafting-wax should then be put on, or narrow strips of waxed cloth may be applied instead, to exclude air and moisture. If possible, the scions should be selected from branches not over ½ inch in diameter when they can be found of sufficient firmness of that thickness. Small lateral shoots having a terminal bud and only an inch or two in length and quite thin will unite by this method very easily. It is not necessary for the scions to be dormant, but they should be fully matured and the leaves cut off to about ½ inch from the buds. The bark slips readily from the time growth begins in spring, so that the operation may be performed at any period during late spring and summer. In the course of about two weeks after the operation is performed, if the scions remain fresh, the probabilities are that a union will have been effected. Part of the top of the stock may then be removed to induce the scion to start growth, and when it has made some headway the top of the stock may be cut off near the scion."
Bark-grafting (Fig. 1701) is an excellent method of grafting fairly large limbs, since it does not injure the stock so much as does the cleft-graft. The scions are cut thin and inserted between the bark and wood. The bark is securely bound to hold it tight, and the entire surface is waxed, as in cleft-grafting. This method is called crown-grafting by the French and English.
This method is useful when it is necessary to graft very large limbs, for the stub does not need to be split and several scions may be set. When large limbs are broken from apple and pear trees, the stub may be trimmed and several scions set around it, to hasten the healing and to afford strong shoots with which to renew the part.
Pelargoniums, chrysanthemums, cacti, and other soft-wooded greenhouse plants are sometimes grafted for the novelty of having more than one variety growing on the same root. Probably most herbaceous plants can be grafted readily, with the exception of the endogens, which do not lend themselves to the operation, although there are examples in which grafting has been successful on them. To succeed with an herbaceous scion, it is necessary that the room be rather close and moist, so that evaporation will not be very rapid. One should endeavor to secure the general conditions that obtain in a good propagating-house. The temperature should be kept rather below the normal for that species until union has taken place. It is usually best to cover the union with moss or some other material to protect the wound and to check evaporation. Best results are secured when the scion is firm in texture, as also in the case of herbaceous cuttings. The kind of graft is of less importance, although it is customary to use the veneer-graft scions, since there is less injury to the stock and the outer surfaces are easily applied to each other. The scion ordinarily consists of one or two joints, and if the leaves are large, they are cut in two, as in the making of softwood cuttings.
Inarching, or grafting by approach.
In those cases in which union takes place with much difficulty, it is possible to effect the conjunction by allowing the scion to grow fast to the stock before it is severed from its own roots. The plant which it is desired to have grow on the stock is bent over to the stock, the sur- grafting, faces of the two are exposed so that the cambiums may be pressed close together, and the two are then bound until union takes place. In some cases a tongue is made in both the scion and the stock, much as in whip-grafting, so that the surface of contact is greater and the parts are held together more securely. When the scion has become thoroughly established on the stock, the scion is severed from its own root and the top of the stock is cut off. This inarching or grafting by approach is also used in the greenhouse when it is desired to transfer the whole top or the whole branch of one plant to another. The illustration (Fig. 1702) shows such a case. Inarching is not much employed in this country in a commercial way.
Inarching is sometimes employed to unite two branches into one for the purpose of making a specimen fruit grow larger. If, for example, a twig of an apple tree is inarched into a limb just back of a fruit, the extra food-supply may cause that fruit to grow larger, and a finer specimen may be secured. This use of the graft is employed only for the purpose of securing extra-fine specimens for exhibition or other purposes.
The seedling-inarch has recently been described in detail by Oliver (Bull. No. 202, Bur. PI. Ind., U. S. Dept. Agric.). Such difficult subjects as the mangosteen, litchi and mango respond readily to this method. The idea is to inarch a very young seedling on an older stock, thereby saving time and securing more wood for further propagation. "Seedlings raised from seeds of new and rare trees, shrubs, and vines may be induced to grow very quickly if used as scions when a few weeks old by inarching to strong-growing plants of other species of the same genus or in some oases on species of other genera of the same family. This has been done recently with such plants as chestnuts, walnuts, hawthorns, oaks, and many others. It is not necessarily done for the purpose of hastening the flowering or the fruiting of new plants, but to give quickly an abundance of material for propagation by budding or grafting when the new material is assumed to be valuable. If a hardwood seedling of hybrid origin is tied to a large stock and they fail to unite, there is little or no danger of losing the seedling, provided its roots are kept damp during the period of making the attempt. If the inarch is not successful, the seedling can be repotted and grown in the usual way."
In Fig. 1703 is shown the method of seedling-inarch. A rose seedling is grown near the side of a pot, it having been pricked off into a 2-inch pot shortly after the cotyledons are developed; it is next shown, after two or three weeks' growth, removed from the pot and tied in a cloth to facilitate handling, a little fresh soil being held in place by the covering; the ball is then secured to the stock, and the seedling is inarched by chamfering the surfaces in contact. When union is complete, the root of the seedling is removed.
For further discussion of the whole subject of grafting, the reader is referred to current works on fruit- growing; also to the two American special books on the subject—Fuller's "Propagation of Plants" and Bailey's "Nursery-Book." In English, Baltet's "Budding and Grafting" is standard. It is an English version of "L'Art de Greffer." L. H. B.
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