Alaska Pioneer Fruit Growers Association

GRAFTING AND BUDDING OF FRUIT TREES

February 9, 1994

By Robert A. Purvis, Department of Horticulture/LA, WSU, Pullman WA 99164-6414

 

  1. Purpose of class: To describe the principles and practice of grafting and budding of fruit trees and to have the student practice the techniques of so doing.

 

  1. Definition and Purpose of Grafting

 

  1. Grafting is defined as the art of connecting two pieces of living plant tissue together so they will unite, form a single plant, and grow.
  2. The purposes of grafting include the following:
  3. To propagate or assist in propagating plant varieties not otherwise conveniently
  4. To substitute one part of a plant for another, as for example in top working an apple tree to a different variety or putting an interstern between a scion and rootstock.
  5. To join plants selected for special purposes or properties, e.g., disease or pest resistance, size control, or adaptability to special conditions of soil or climate.
  6. To repair bark damage or girdling by rodents.
  7. To overcome, stock/scion incompatibility.
  8. To invigorate weak-growing plants.
  9. To enable one root system to support more than a single variety.
  10. To do virus-indexing of plant material.
  11. To hasten the initiation of flowering and fruiting.

 

III.       Terminology

 

  1. Scion – a part, of a plant used for grafting upon an understock. In whip-and-tongue grafting, generally it is a piece of 1-year-old wood 3-5 inches long.
  2. Rootstock (also, stock or understock) – The bottom part of a plant propagated by grafting or budding, consisting of a root system and stem or trunk.
  3. Xylem a network of tubes and vessels which conducts water and mineral nutrients from the roots to the rest of the plant.
  4. Phloem – a network of tubes and vessels which conducts photosynthates from the leaves downward to the rest of the plant.
  5. Meristem – tissue capable of cell division.
  6. Cambium – a layer of meristematic tissue between the xylem and phloem from which new cells develop.
  7. Callus-scar tissue arising from the cambium at wounds, which helps to form a graft union.
  8. Polarity – tendency to develop from the poles, roots downward, stems upward. Polarity must be observed for successful grafts.

 

  1. Preparation for Grafting

 

  1. Preparation of Rootstocks

 

  1. Order rootstocks in fall to early winter to be sure that what you want is available.
  2. Order by caliper – typically 1/4 to 3/8 inch for grafting medium size to large scions, No. 1 to 1/4 inch for smaller scions. (Even 3/8 to 5/16 rootstocks will work well, but they will require large scions and may be difficult to cut.)
  3. Arrange for delivery shortly before you want to graft.
  4. Roots should be kept moist but not wet. Inspect rootstocks upon arrival and store at 32 to 40F.
  5. If roots are very dry, soaking them for several hours before grafting may raise the water content of the cambium, leading to better callus formation and a higher number of “takes” (successful grafts).

 

  1. Preparation of Scions

 

  1. In September or October, decide which cultivars you want to propagate in the spring.
  2. If freezing damage is likely to occur, gather some scions after the leaves drop but before severe winter temperatures occur. Otherwise, wait until late winter and cut scion when temperatures are above freezing.
  3. Select new wood, preferably from the sunnier side of the tree, from a tree which has already come into fruiting. Ideally, there should be at least a foot of new growth on the branch selected, and 2 to 3 feet is much better.
  4. The scions should be 5 to 12mm in diameter: the thicker the scion, the more vigorous is from it as a rule.
  5. Select wood free of insect and disease problems and winter injury. Seal the cut ends with wax. Virus indexed wood is best.
  6. Store in a plastic bag with a moist (not wet) paper towel. The idea is to keep the external moisture level the same as that inside the scion. Keep scions at 30 to 35F, and do not store them with sources of ethylene (e.g., ripe fruit), which promotes budbreak.
  7. The ideal to strive for is to keep the wood fully dormant and neither to allow it to dry out nor to become moldy, until it is to be used.
  8. Protect scions from rodents.

 

  1. Other materials needed

 

  1. Tree-Doc, wax, or other material to waterproof the graft union.
  2. Masking or electrician’s tape, or other tying material to hold the scion securely in place.
  3. Labeling materials – tags, waterproof and fade-proof marking pens.
  4. Sharp knives, preferably with wide, thin blades.
  5. A good quality sharpening stone.
  6. Pruning shears or loppers to cut lengths of scionwood or shorten rootstocks.
  7. Wet burlap or other means of keeping the roots moist.

 

  1. Physiology of Grafting

 

  1. Stock/scion compatibility

 

  1. Normally, one grafts apples to apple or crabapple rootstocks (Malus to malus, in other words).
  2. Pears are grafted to pears – seedling Pyrus communis, Old Home X Farmingdaie 40, 51, 333, 513), or to quince in areas with mild winters.
  3. Cherries are normally grafted to Prunus mazzard or Prunus mahaleb rootstocks, crosses of the two, or to semidwarfing rootstocks such as GM 9, 61, or 79.
  4. Plums may be grafted to plum, peach, apricot, or almond rootstocks. “Pixie” is a semidwarfing plum rootstock compatible with both European, Japanese, and American hybrid plums. Prunus salicina mandshurlca is a very hardy, vigorous rootstock likewise compatible with all three types of plums. Prunus americana, the native American plum, is best used with Japanese or American hybrid plums, and Myrobalan plum rootstocks are best for European plums.
  5. Peaches may be grafted to peach, apricot, or some plum rootstocks, e.g., St. Julian A.
  6. Apricots are grafted to apricot, peach, or some plum rootstocks.
  7. Viruses may cause incompatibility and graft failure.

 

  1. Role of temperature, moisture, and oxygen

 

  1. Production of callus tissue does not occur below 32F.
  2. Formation is slow even at 38F but increases up to 90F.
  3. Temperatures above 91F will kill callus tissue; that below 28F will injure it.
  4. Callus tissue is very high in water content. The water needed to form it is drawn out of the limited reserves within the scion and the somewhat greater reserves of the rootstock.
  5. For this reason, anything that causes or allows a loss of water from the scion will diminish the odds of getting a take.
  6. Storing scions above 40F will result in needless callus formation and probable budbreak, both of which will deplete the water in the scion.
  7. If no callus tissue forms, no graft union will form.
  8. Avoid asphaltic preparations such as pruning sealant for use in coating graft unions.

 

  1. Formation, of the Graft Union

 

  1. Soon after knife cuts are made, damaged surface cells brown and die.
  2. Freshly exposed eambial surfaces and parenchymal cells adjacent to the cambium will begin to form callus tissue, which is made from thin-walled parenchymal cells, if
  3. grafting cuts are well matched,
  4. scions are bound snugly to the rootstock,
  5. grafts are given proper aftercare.
  6. Parenchyma cells slowly form a healing tissue over any exposed scion surface from the cambial area.
  7. The first cell division in a fresh cut will occur after 24 hours.
  8. Under perfect conditions, callus tissue will form a new cambial bridge within 5 days. After another 5 days, there will be some differentiation into xylem and phloem within the bridge.
  9. Within 15-20 days after grafting, the vascular bundle should be well differentiated into xylem and phloem. After this, the scion’s buds can safely begin growing.
  10. With the passage of time, deposits will be laid down in the new cells to strengthen them and the union.
  11. The callus tissue cells cannot keep themselves from drying out. Hence, it is important to keep scion buds dormant and to keep the graft from drying out also.
  12. When preparing a scion, avoid using the top and bottom inch or two of a cutting.

 

  1. Making the Whip-and-Tongue Graft

 

  1. Preparation of the scion

 

  1. From a piece of first-year growth, cut a 3-5 inch long piece to serve as a scion. There should be a minimum of two, and preferably 3-4 buds on the scion. Also, make a label for the tree (listing the scion, rootstock, and date grafted, as for example, Red Delicious/Malling 26, 3-12-90) at this time.
  2. Begin on the side opposite to the basal bud on the scion, to make a tapering downward cut 4-5 times as long as the scion diameter. (Note: the buds point toward the apical or upward end of the scion.)
  3. The cut should he smooth, flat-surfaced to slightly concave. Note that longer cuts allow more area for matching the cambia.)
  4. Begin the tongue cut about halfway from the basal tip of the scion to the center of the cut surface. Pull the knife so the tongue is almost parallel to the original cut. The tongue should be about 1/3 as long as the first cut.
  5. The tongue serves to provide a more secure union between scion and rootstock and also more area for intercambial contact.

 

  1. Preparation of the rootstock

 

  1. Keep rootstock roots moist.
  2. Paine off suckers and lateral branches from the rootstock.
  3. Look for a smooth, straight stretch of trunk that is the same diameter as the base of the scion. Cut off the top of the rootstock above that.
  4. Next, make a smooth, slanting cut the same length as the cut on the scion, towards the apex of the rootstock.
  5. To form the tongue, begin a cut at a point halfway from the tip of the rootstock to the center of the cut surface and cut semi-parallel to the first cut. This cut should be 1/3 as long as the first cut.

 

  1. Fit scion and rootstock together so that the tongues interleave.

 

  1. Cut off any overlap of the tips of scion or rootstock beyond the cut surfaces,
  2. Align the cambia (the bright green oval on each cut surface). Ideally, both sides should match. At worst, one side should be matched as well as possible. Remember, the more the cambial tissues are matched, the more likely it is you will get a take. Align the cambia, not the bark!
  3. Wrap graft union spirally with 1/2-inch wide masking tape. The spirals should overlap only a little; the tape should be snug but not ultra-tight.
  4. Apply Tree-Doc over cut tip of scion and over the union, or dip the newly grafted tree upside down very quickly into a wax bath so the union and scion are sealed. The wax temperature should not be over 185F; 160 to 185F is best.

 

VII.     After-Care of Grafts

 

  1. The roots of the freshly grafted trees should be kept moist by burying them in a bin of moist wood shavings or potting soil. Before burying, any broken roots should be trimmed off. The tips of sparsely rooted laterals should be cut off to encourage new root growth.
  2. The trees should be kept at a temperature of 40-50F for apples and pears, 50-60F for stone fruits.
  3. Remove suckers from below the graft union.
  4. Once leaves begin to sprout from the buds (typically 10 to 20 days after grafting), the trees may be planted in pots or in the ground.
  5. Causes of graft failure:

 

  1. Drying out of the graft union owing to an imperfect seal (most common cause),
  2. Poor alignment of cambial layers of scion and rootstock,
  3. Scion breaking dormancy; insufficient amounts of water available to form callus tissue,
  4. Viruses,
  5. (Later in the spring) Bridge of cambial tissue is too narrow to support leaves or vigorous growth.

 

VIII.    Chip Budding.

 

  1. Introduction

 

  1. Chip budding is the substitution of a scion chip (consisting of the bud, bark, and a sliver of wood) for a matching area of rootstock tissue. It offers an advantage over whip and tongue grafting by economizing on scionwood.
  2. Other advantages:
  3. It offers better contact of cambial layers than T-budding,
  4. it oftentimes gives 50 to 100% more takes on species with a low success rate using other techniques,
  5. It does not require that the bark “slip” on the rootstock,
  6. It offers greater resistance to cold temperatures for buds emplaced during the summer months.
  7. Chip budding is normally done in the summer at the same time as T-budding or in the spring just as the sap begins to rise in the rootstock.
  8. Scionwood selection is the same for spring chip budding as it is for whip and tongue grafting. For summer budding, choose new growth with plump buds, and cut off all but 1/4 to 1/3 inch of the leaf petioles after cutting the shoot.

 

  1. Techniques
  2. Choose an area of smooth, clean stem, 4 inches aboveground.
  3. Make a downward cut, 1/8 inch long, at a 45 degree angle to the bark.
  4. Make a second cut, 1 to 1-1/2 inches above the first and 1/8 inch below the surface, downwards to meet the first cut. Remove and discard the chip formed.
  5. The top of the cut should be like an inverted U rather than a V.
  6. The woody tissue should be exposed on the rootstock.
  7. To prepare the bud chip,
  8. Hold the budstick so its base points toward you.
  9. Make a cut 1/8 inch long at a 45 degree angle to the bark in a downward direction, 3/4 inch below the bud chosen.
  10. Begin 1 to 1-1/2 inches above the first cut and cut downward to the first, 1/8 inch below the surface. The object is to cut a chip that will be slightly shorter and narrower than the area exposed on the rootstock.
  11. Insert the chip on the rootstock so that it sits on the ledge formed by removal of the rootstock chip.
  12. Align the edges, or at least one edge, of the chip with the exposed cambium on the rootstock.
  13. Wrap the area of the chip spirally with Parafilm, a grafting rubber, or thin polyethylene film.
  14. Remove the wrapping material 4-6 weeks later. If the bud union has formed, the bud will not fail out when the wrapping is removed, and you should see the callus formation through the material.

 

  1. Spring chip budding

 

  1. Use the same criteria for scionwood selection as given in section IV.B.
  2. After making the chip bud union, keep rootstocks at 60F to cause growth and a good flow of sap.
  3. After 3 weeks, check to see if the chip has formed a union. If it has, the bud should be swelling, or at least firmly joined.
  4. If the bud is joined, cut the rootstock off about 4-6 inches above the bud. This will eliminate the rootstock’s apical dominance and suppression of the bud’s growing. Once a few inches of shoot growth have emerged from the bud, cut the remaining snag off 1/4 inch above the bud union.
  5. The roots should have a supply of moisture after the chip budding is done so that there will be ample amounts of sap flow and cambial activity.

 

  1. Last thoughts

 

  1. If after all effort, a whip-and-tongue or chip-bud graft fails to take, remember that the rootstock, especially if it is making healthy growth, can be re-used for another attempt, either of summer chip budding or of whip-and-tongue or chip budding the following spring. If the second attempt fails, it’s probably best to discard the rootstock and begin afresh on a new one.
  2. Scionwood is best cut as soon before use as possible to insure its freshness.