- Growing Fruit: Grafting Fruit Trees in the Home Orchard [fact sheet]
- Why graft?
- What are the limitations?
- What can be grafted?
- When is the time to graft?
- What materials are needed?
- What grafting technique?
- Grafts with similar scion and understock sizes
- Grafts with small scions and large understocks
- Grafting tips
- Whip and tongue graft
- How to Graft Pine Trees
- Collecting Scions
- Whip Graft
- Cleft Graft
- Side Graft
- Is root grafting a positive, cooperative behavior in trees?
Growing Fruit: Grafting Fruit Trees in the Home Orchard [fact sheet]
Grafting as a means of propagating fruit trees dates back several thousand years or more. Grafting is used for two principal reasons: most fruit trees don’t come true to seed (seeds from a McIntosh apple won’t grow into McIntosh trees) and cuttings don’t root easily. The technique of grafting is used to join a piece of vegetative wood (the scion) from a tree we wish to propagate to a rootstock.
Grafting is a fun way to get more enjoyment from your home orchard. You can use grafting to create trees with several varieties or to introduce new varieties into your home orchard. Grafting can also be used to change varieties of trees in your existing orchard (see Cleft Grafting, below).
Remember that you are almost always limited to grafting within a species… most apple varieties are compatible with each other as are most pears. You cannot graft an apple scion on a pear rootstock or vice versa.
Choice of rootstock
Today we have a wide range of rootstock choices that will produce trees of varying sizes, from full-size “standard” trees to true dwarfs (less than 10 feet tall at maturity). Different rootstocks vary not only in final tree size, but also in their winter hardiness, resistance to certain insects and diseases, and performance in various soil drainage types. Most dwarf rootstocks are also precocious, meaning that they bear fruit early in the tree’s life.
Rootstocks are propagated either by seed (for seedling rootstocks), or by the process of rooting cuttings, known as layering. Dwarfing rootstocks are usually rooted cuttings (Fig. 1). Several nurseries offer rootstocks in small quantities to home growers interested in grafting, and many nurseries offer fruit trees on a wide selection of rootstocks. Descriptions of some of the common apple rootstocks follow.
Figure 1: Rooted rootstock layer.
Seedling: Seedling rootstocks produce large trees that are very difficult to prune, harvest and manage for pests. Seedling rootstocks are not recommended for use in home gardens. Few home gardens have space for these large trees and the wait until first fruit will discourage most growers. In addition, pest control with these large trees is very difficult, usually requiring power equipment for spray application. However, these trees may have value when used for wildlife plantings. They cost less than trees with dwarfing rootstock and will grow rapidly, soon outgrowing the browse reach of deer if provided protection for just a few years
M.7 (Malling 7): M.7 was the dominant dwarfing rootstock in NH orchards for many years. It produces a semi-dwarf tree that reaches 15 feet in height and needs 15 feet of lateral space. Fruiting usually begins by the fifth year from planting. M.7 has some weaknesses, for example, it produces numerous root suckers that must be cut each year. On the positive side, M.7 is tolerant of collar rot, a major soil-borne disease of apple. Further, most varieties grafted on M.7 are very fruitful. Apple trees on M.7 should be staked to provide trunk support for the first four or five years.
M.26 (Malling 26): M.26 is an excellent apple rootstock for home gardens. It is precocious, often bearing some fruit as early as the year after planting. It is quite hardy and should do well in reasonably well-drained soils throughout NH. It produces very few root suckers. It needs support (preferably a stake that will last the life of the tree), and it produces fleshy root initials (called burr knots) on the above-ground portion of the rootstock. These burr knots are attractive to borers. M.26 is also susceptible to the bacterial disease fire blight. Plant the tree with the graft union only an inch or so above ground so less rootstock is exposed. Most varieties on M.26 can be planted at an 8-foot spacing.
Bud 9 (Budagovsky 9): This is the number one choice for NH home gardens if a fully dwarf tree is desired. This rootstock is productive, very precocious and when mature, trees on this rootstock stand only seven to eight feet tall. It should be staked to provide support for heavy crop loads. It is very hardy and should do well throughout NH. Apple trees on Bud 9 rootstock can be set at 7-foot spacing in the home orchard.
Selecting and Storing Scion Wood
Several nurseries sell scion wood. Other sources of unique varieties are commercial orchardists in NH and other home fruit growers. Scion wood is collected while trees are still dormant (usually in late February or March in NH). Scion wood should be straight and smooth and about pencil thickness (Fig. 2). Water sprouts that grow upright in the center tops of trees are ideal.
Figure 2: Scion wood.
Once cut, trim to 12-18” lengths, and place in a food-grade plastic bag. Place a damp paper towel or sphagnum moss in the bag to maintain moisture, seal, and place in the refrigerator until you are ready to graft, usually in mid- to late April.
Many newer varieties of apples and pears are patented. Propagation of patented varieties requires the permission of the patent holder along with a royalty fee for each new tree created.
Whip and Tongue or Bench Grafting
A technique commonly used for spring grafting is whip and tongue grafting, also known as bench grafting. Whip and tongue grafting can be used to add multiple varieties to an apple or pear tree already growing in the home orchard. Because this technique involves joining wood of equal or nearly equal diameter, generally about pencil thickness, whip and tongue grafting is done near the ends of branches.
To complete this graft, you will need a sharp knife and either grafting tape, masking tape, or a plastic strip to seal the graft. The first cut is a smooth cut approximately 1¼ to 1½ inch long, made with a single knife stroke (Fig. 3). This cut is made on the rootstock several inches above the top root. A matching cut is made on the bottom of a 5-6 inch long piece of scion wood.
Figure 3: The face cut should be made with a single stroke of the knife and come to a sharp point.
Figure 4: The tongue cut. A sharp knife is essential.
The second cut is a bit more difficult to make. Start by holding the wood as shown in Fig. 4. Starting at a point about ⅓ inch down from the tip of the cut surface, cut down into the center of the rootstock. This cut should be nearly parallel to the grain of the wood (Fig. 4). The bottom of the scion should be prepared in exactly the same fashion as the top of the rootstock.
Join the two prepared pieces, scion and rootstock (Fig. 5). Push the two together firmly to insure a snug fit and good contact. Finally, wrap the new graft union to protect tissue from drying. Masking tape is one option. Another is specially developed grafting tape. (Fig. 6). I prefer to use 1 inch wide strips of plastic cut from bread bags. Start below the newly formed union, stretching the plastic slightly as you wrap around and up over the union. This will help insure a moisture proof seal. Once the union is completely covered, tie the plastic strip off with a simple knot. A healed whip and tongue graft is shown in Fig. 7.
Figure 5: Scion and rootstock are joined to complete the graft.
Figure 6: The completed whip and tongue graft, sealed with grafting tape
Figure 7: A healed whip and tongue graft.
Newly grafted trees are set out in a nursery row to grow. The home vegetable garden is an ideal place to grow these trees out for a year or two until they are large enough to plant out in their permanent location. When planting grafted trees, be sure to set the graft union 2” (Fig. 8) or so above ground to ensure that the scion does not root.
Figure 8: Set trees so the graft union is a couple of inches above ground. If the scion (variety) roots, a large tree will result.
Cleft grafting is a technique that produces a union between a large rootstock trunk or limb and a much smaller scion. Using this method, an older tree can be top-worked to change to a more desirable variety.
For this method, scion wood is collected and stored as described for whip and tongue grafting. Again, this grafting is done in April in NH.
The first step in cleft grafting is to prepare the older tree for top-working. The tree is cut off at a convenient height, usually 30 inches or so above ground (Fig. 9). Alternatively, individual branches within an older tree can be top-worked using this same technique.
Figure 9: Older apple tree, cut off about 30 inches above ground in preparation of cleft grafting.
Using a hammer and either a cleft grafting tool designed for this use or alternatively, a hatchet or chisel, a split or cleft is made in the wood (Fig. 10). This cleft is then held open using the end of the cleft grafting tool designed for that purpose, or a screw driver or similar tool (Fig. 11).
Figure 10: A cleft or split made using a hammer and cleft grafting tool.
Figure 11: The cleft is held open using the end of the cleft grafting tool designed for that purpose.
Once the stock is prepared, scions are cut and inserted to complete the graft. Two scions are prepared using pieces of pencil-thick, year old wood, approximately five to six inches long. The bottom of each scion is prepared by making a single, smooth, sloped cut on each side (Fig. 12).
Figure 12: Bottom of scions used for cleft grafting. The thicker side should be set to the outside of the stock.
These scions are set into the cleft, one on each side, positioned so that the cambial zones of the stock and scion ‘line up’ or touch (Figs. 13, 14 and 15). It is important to note that the bark of the stock is much thicker than that of the scion. The key is to line up the cambial zones, not the outside edge of the bark of each.
Figure 13: The knife point marks the cambial zone of the stock. It separates the bark from the hard wood inside.
Figure 14: Scion properly inserted into cleft in stock, assuring cambial zone contact.
Figure 15: A completed cleft graft – sealing with grafting compound is the next step.
If the stock is larger than four or five inches in diameter, I like to insert additional scions using a technique called inlay or bark grafting. Scions are prepared as shown in Fig. 16. Again, a four to five inch scion is used. A one-inch long cut is made up the middle of the scion from the bottom, and one side is removed. The other side is often tapered at the tip to make joining the scion to the stock easier.
Figure 16: A scion prepared for use in inlay or bark grafting.
Place the flat, cut surface of the scion flat against the stock and trace the sides into the bark of the scion with a knife. Then cut the bark in all the way to the hardwood using the tracings as a guide. Carefully peel back the bark and slide the scion in until it seats (Fig. 17). Using the bark flap as a cushion, nail the scion in place using a wide headed, wire nail (Fig. 18).
Figure 17: Scion seated in slot cut in bark of scion.
Figure 18: Scion nailed in place.
Insert scions up to every four inches in stock circumference. After a scion has been placed in each side of the cleft and inlay grafts have been added, all cut surfaces must be covered to prevent drying of sensitive cambial tissue. Use a commercially available grafting compound for this purpose. Check newly made grafts for several days to insure that no holes in the grafting compound have opened (Fig. 19).
Figure 19: Grafting compound must cover all cut surfaces of the stock and scion. Be sure to cover the cleft or split in its entirety, including on the side of the trunk.
What Comes Next?
If the grafts were made correctly, most will grow, some quite vigorously. These grafts will be brittle for a few years, so proper training is important.
The spring following grafting, select two successful grafts and join them together by wrapping the weaker one into the stronger one and tying it off with black plastic electrical tape. Over time, these wrapped shoots will graft together and create a very strong, natural bridge (Fig. 20).
Figure 20: Wrapping the two successfully greafted scions together creates a very strong structure.
Proper tools and supplies make the grafting job easier. There are several good grafting compounds on the market. Those that do not need heating are easier to use. While a hatchet can be used to make cleft grafts, a cleft grafting tool is relatively inexpensive and makes the job easier. Lastly, A sharp knife is your most important grafting tool and it makes sense to purchase a high quality one.
Download the Resource for the complete fact sheet and a printable version.
“In areas where we have a high level of Verticillium, we are seeing increased yield with grafting, mainly because the non-grafted plants don’t yield well,” Miles says. “So we see an increase in fruit number at harvest.”
Miles is part of a national team of researchers focused on vegetable grafting funded by the USDA Specialty Crop Research Initiative (SCRI).
In this interview, Miles shares her research results with American Vegetable Grower® magazine on grafting watermelon and eggplant, including improvements in yield, the grafting process, benefits for growers, and more.
Q: How are the grafted plants responding to soilborne diseases?
Miles: The grafted plants are holding up well to Verticillium, and it really depends on the level of disease in the field. At relatively low levels, we don’t get a big difference due to grafting; but as the levels start to go up, you see a much greater difference between grafted and non-grafted plants.
The important thing to understand is that with watermelon, we don’t really have resistance for Verticillium wilt. What we have is tolerance. We get a three-week delay in disease onset and usually that gives us time to harvest the plant. At the end of the season, we do a stem assay of plants in the field. We look in the stem and we’re seeing the disease there, but it’s not necessarily exhibited by wilting or chlorosis.
Eggplant is more susceptible to Verticillium wilt than watermelon. We have not found a really strong tolerant rootstock. So, even with grafting, we have not prevented the disease. We’re still looking, but we haven’t found it. And at this point, unfortunately, Verticillium wilt is not simple to manage for eggplant.
Q: How are you grafting plants?
Miles: For eggplant, we use what’s called the splice graft.
Images courtesy of Washington State University
The splice is made below the cotyledons, and we do that at the seedling stage. It’s done at a 45° angle below the cotyledon so that both cotyledons are removed from the rootstock. That’s important because it removes the meristem tissue that’s in the leaf axil of the cotyledon, which would give you rootstock re-growth. You don’t want your rootstock to overgrow the variety you’re grafting on, so we remove both cotyledons from the rootstock.
And for watermelon, we use what’s called a one-cotyledon splice, which also is a splice graft, but it’s a little bit different because you leave one cotyledon on the rootstock. This is a 65° angle cut, so we leave one cotyledon on the rootstock, and then we scrape the base of the cotyledon with the edge of the cutting blade to take out the meristem tissue to prevent the regrowth.
Images courtesy of Washington State University
All of the grafting is done by hand, and we don’t do a lot of plants. We just do the plants for our research trials, which is maybe 500 or 600 plants per project.
Q: Is there any talk of automation for grafting plants?
Miles: A lot people are interested in automation. There are definitely grafting robots or grafting aids out there; however, they are still relatively expensive. It comes down to volume, and you have to be producing a relatively high number of plants to make it worth the investment. In our case, and for most small-scale growers who are grafting their own plants, it’s definitely not worth it.
Furthermore, a lot of these machines still require people to manage them, and the reality is that people can work pretty fast doing it by hand. In most cases, people can graft up to 300 eggplant or tomato plants per hour by hand and up to 250 watermelon plants per hour.
Q: What is the cost/benefit analysis to use grafted plants?
Miles: What we’re finding here in Washington is that you can use a grafted plant to control a disease, so you don’t necessarily have to use a fumigation application. If you look at using grafted plants instead of fumigation, then you can compare those costs. Also, for organic growers who don’t have access to fumigation, grafting provides them with an alternative disease management that they don’t have at all. Grafting is a very effective technique, and at a very low cost.
Q: What has been the grower reception with grafted plants?
Miles: There are a lot more grafted plants used in the U.S. today than there were even a couple of years ago; however, the U.S. has been slower to the game than our neighbors in Canada and Mexico.
What we need are really good demonstrations with various growers to show what a field of grafted plants looks like. Whereas in other areas in the world, they have maybe 10 acres, our growers have hundreds of acres. and we don’t have the capacity to make that number of grafted plants and demonstrate particular combinations.
However, this year, we’re going to start to see the beginning of more grafted plants and combinations as there are more grafters that can customize plants for growers.
Q: What are the research plans moving forward?
Miles: With watermelons, we’re interested in increasing the efficiency of grafting. We also want to increase the survival of grafted watermelon transplants in the grafting room.
One simple change we’ve made with watermelon is that we’ve gone from cutting at a 45° angle to a 65° angle. We feel the larger cut surface area gives a better take on grafting. We think this allows the vascular bundles to conjoin more quickly and completely between the rootstock and scion, providing water and nutrient transport between the top and bottom of the plant.
Alexander is a freelance writer and regular contributor to American Vegetable Grower® magazine.
Alexander is a former associate editor with American Vegetable Grower® and currently a contributing writer in Denver, CO. See all author stories here.
Ray R. Rothenberger and Christopher J. Starbuck
Department of Horticulture
Grafting is the act of joining two plants together. The upper part of the graft (the scion) becomes the top of the plant, the lower portion (the understock) becomes the root system or part of the trunk. Although grafting usually refers to joining only two plants, it may be a combination of several. A third plant added between two others becomes the trunk or a portion of it. This is called an interstem. Multiple grafts may produce an apple tree with several varieties or a rose-of-Sharon shrub with several different colors of flowers.
Some cultivars (varieties) of plants do not come true from seeds. Others are difficult or impossible to reproduce from cuttings or other propagation techniques. Grafting (topworking) is a way to change a large tree from an old to a new variety. It is also a method of using a root system better adapted to soil or climate than that produced naturally by an ungrafted plant. By using special understocks or interstems, grafting is a way to produce dwarf plants.
What are the limitations?
Not all plants can be grafted. Generally, only plants closely related botanically form a good graft union. Grafting is not a means of developing new varieties. The stock and scion must be compatible. Incompatible grafts may not form a union, or the union may be weak. A poor union results in plants that either grow poorly, break off or eventually die.
The compatibility of plants has been determined through many years of trial. There is no other way to determine whether or not two plants will produce a good graft union. This publication will help you make a decision about the possibility.
What can be grafted?
Most varieties of a particular fruit or flowering species are interchangeable and can be grafted. Because of differences in vigor, some are better able to support others as understocks. For example, although a union is possible, sour cherry is not a good understock for sweet cherry. Sweet cherry is more commonly grafted onto Mazzard (Prunus avium) or Mahaleb (P. mahaleb) seedlings.
Plants of the same botanical genus and species can usually be grafted even though they are a different variety. Plants with the same genus but of a different species often can be grafted. But the result may be weak or short-lived, or they may not unite at all.
Plants of different genera are less successfully grafted, although there are some cases where this is possible. For example, quince, genus Cydonia, may be used as a dwarfing rootstock for pear, genus Pyrus.
Plants of different families cannot be grafted successfully. Although it has been reported that relatively short-lived grafts of herbaceous plants of different families have been made, there is no successful practice for commercial or home grafting of woody plants of different families.
It is sometimes believed that two plants can be made into a genetically different plant by the process of grafting. However, there is no basis for this idea. Although there are cases where a different type of shoot develops from the graft union, this is the result of a chimera, a type of mutation. This is not a true intermingling of the genetic structure of two different plants as occurs in seed-produced hybrids.
When is the time to graft?
Most grafting is done in late winter or early spring before new growth begins. The best time is after the chance of severe cold has passed but well before hot weather arrives. Scion wood may be collected during the winter. Store it in a cold, moist place at temperatures close to 34 degrees Fahrenheit. At home, a few scions could be stored in a plastic bag in the refrigerator with moist paper towels, or they could be dipped in paraffin so they retain moisture.
What materials are needed?
A good-quality knife, able to hold a sharp edge, is the key to good grafting. Although special grafting and budding knives are desirable, you can use almost any good pocketknife. Keep material to sharpen the knife handy.
- Grafting wax
After the graft is made, some covering must be used to keep it from drying out. Either hand wax or brush wax may be used. A hand wax is most commonly used for home grafting. It is softened by the heat of the hand and can be easily applied. Heated waxes may be brushed on, but make sure the wax is not too hot. Heat could damage the tender cambial tissue.
- Grafting tape
This is a special tape with a cloth backing that decomposes before girdling can occur. Tapes may be used for binding grafts where there is not enough natural pressure. Electrical and masking tapes are also used. Masking tape is suitable where little pressure is required, as in the whip graft.
- Budding strips
Budding strips are elastic bands. They look like a wide rubber band that has been cut open. Budding strips secure several types of grafts with small stocks and scions.
Veneer, bridge and inarching grafts require long, thin nails. Half-inch nails are long enough for most grafts, except for bridge grafting, which may require 3/4-inch nails.
- Grafting tool
Specially designed tools have been developed for grafting. The most common one is used for cleft grafting. It has a blade used to split the stub and a wedge to hold the split open while the scions are inserted. If this tool is unavailable, use a heavy knife and a fairly wide wedge, at least 2 inches long, for cleft grafting. Use a mallet or hammer to pound the grafting tool or heavy knife into the stub. Split the stub and insert the wedge to open the split.
What grafting technique?
Grafting techniques can be divided into two basic types, which are largely determined by the size of the understock. In some cases, a graft may be made to join a scion and understock of nearly equal size. The other type attaches a small scion to a much larger understock. In this case, several scions may be attached to the understock as in cleft or bark grafting.
A. Cuts for the whip graft must be smooth and straight.
B. Cut again to form the tongue.
C. Push stock and scion tightly together.
D. Wrap graft to keep cuts tight and to prevent drying.
E. Whip and tongue graft with scion attached to root system.
Grafts with similar scion and understock sizes
Whip graft, bench graft
The whip graft (Figure 1) is fairly easy and heals rapidly. It works best when the stock and scion are of similar diameter, preferably between 1/4 and 1/2 inch.
The stock can be either a plant growing in the field or a dormant bareroot plant as in a bench grafting. The stock should be smooth and straight-grained. Do not graft near a point where side twigs or branches have developed.
The scion should be 1-year-old wood, preferably the same size as the stock. If the stock is larger than the scion, contact can be made on only one side. The scion should never be larger than the stock.
- Preparing the stock and scion
For this technique, the cuts made in both stock and scion should match. On both parts, make a smooth sloping cut 1 to 2-1/2 inches long depending on the thickness of the material (Figure 1a). Make the first cut with a single, smooth cut with no waves or whittling. The beginner should practice by cutting extra twigs. A good-quality, sharp knife is essential.
- Cutting the stock
The stock may be (for a bench graft) a stem and root system of a young plant or a piece of root. Make a slanting cut about 2 inches from the butt (start of root system) of the young whip.
Although grafts may be made with a simple union of two slanting cuts, the strongest graft results from a whip-and-tongue system (Figure 3). To form the tongue, hold the one-sided, slanting cut facing you and support it with your finger. About one-third down from the tip of this cut, make a downward cut about 1/2 inch long as close to parallel with the grain of the wood as possible (Figure 1b).
- Cutting the scion
The cutting procedure should be exactly the same as that for the stock. The only difference is that the cuts are made at the bottom of the scion piece, whereas they were made at the top of the stock. The more similar the cuts on the two pieces, the greater chances of a successful graft union.
- Fitting the stock and scion
After the cuts are made on both parts, push them together tightly enough so that the cut surfaces match as closely as possible (Figure 1c). The cambial area (area immediately under the bark) of both pieces must be aligned for a union to develop. If the scion and stock are not the same size, match the cambiums on one side only. The lower tip of the scion should not hang over the stock.
- Wrapping the graft
In most cases, it is safer and better to wrap the graft to keep it tight to prevent drying (Figures 1d and 1e). Wrap the graft with a rubber budding strip, grafting tape or a plastic tape such as electrical tape. If the wrapping material does not decay naturally, cut it about a month after growth begins.
To prevent the graft union from drying, the area should be waxed. Cover the wrapped area with wax as uniformly as possible. In wrapping and waxing, be careful not to dislodge the aligned cambial areas.
A. Cut stock smoothly. Trim any rough edges with a knife.
B. Split stock, and open with a grafting tool.
C. Make a long, smooth cut to prepare scion.
D. Cut again to make a pie-shaped wedge.
E. Promptly insert scion into stock after cutting.
F. Cambium layers must match closely.
G. A very slight slant can ensure cambial contact.
H. After insertion, wax thoroughly to prevent drying.
I. After the first year, shorten one scion to allow the other to develop.
Grafts with small scions and large understocks
The cleft graft
The cleft graft (Figure 2) is most commonly used to topwork a tree; that is, to change from one variety to another. It can be used on either young or mature trees. Young trees may be cleft grafted on the trunk, while older trees are grafted on branches not more than 2-1/2 inches in diameter. Branches fully exposed to sunlight and in the main stream of sap flow are more successful than those in shaded or inactive areas. Grafts on upright branches grow better than those on horizontal branches.
- Preparing the stock
Branches of large trees or the trunk of a small tree must be sawed off to provide a stock for the scions. Select a smooth, knot-free, straight-grained section. Saw the branch off at a right angle to the grain (Figure 2a). Don’t tear or split the bark. If the saw cut is not smooth, use a knife to trim off the rough edges. The bark must be tight to form a successful graft. Using a grafting tool, or a heavy knife that may be tapped with a mallet, drive the blade into the stub to split the stock through the center so a split extends about 2 inches into the branch (Figure 2b).
- Preparing the scion
The scion for the cleft graft should be made from 1-year-old wood about 1/4 inch in diameter. Usually, it is best to cut the scion long with three buds so it can be inserted with the lowest bud just above the stock. Always note which is top and bottom of a scion stick. A scion will not grow if inserted upside down.
Start below the lowest bud, and make a long, smooth cut toward the base(Figure 2c). The cut should have a surface 1 to 1-1/2 inches long. Turn the scion to the opposite side and make a second smooth cut of the same length so that one side (the side containing the lowest bud) is slightly thicker than the other side (Figure 2d). The wedge that is formed does not need a sharp point; a blunt point is preferable. Do not use more than three buds. If wood is scarce, two buds should give good results.
- Inserting the scion
With a grafting chisel or a small wedge, open the crack wide enough to insert the scion easily (Figure 2e). Insert the scion with the thicker side toward the outside with the cambiums in contact (Figure 2f). Although maximum contact is obtained with straight positioning, a slight slant may help ensure contact (Figure 2g). The best contact point is about 1/4 inch below the shoulder of the stock. After properly positioning the scion, remove the wedge or chisel from the slit. The pressure of the stock against the scion should be greatest where the cambiums touch. When the scion is placed in the crack, the cut surface of the scion wedge should be almost entirely hidden.
Two scions are usually inserted in each slit, one at each side. This gives a better chance for getting at least one graft to grow.
- Waxing the cleft graft
The cleft graft should be waxed so that all cut surfaces are covered (Figure 2h). Cracks sometimes develop as the wax sets. Check wax after a few days and again after several weeks to ensure that all surfaces are kept covered.
- Caring for the graft
After the graft begins to grow, it must also be given attention. During the first season, don’t prune branches that grow. Grafts that grow vigorously may need to have the tips pinched out to stimulate branching. Very long shoots may break loose during strong winds. Cleft grafts should grow vigorously and need only light pruning to shape their development (Figure 2i). Never prune heavily.
After the first year, some training and branch selection may be necessary. Do this at the usual pruning time in late winter or early spring. If both scions in a cleft grow, shorten one to allow the other to develop and become dominant. Do not remove the second graft until later, because it will help to cover the wound faster.
In topworking large trees, it is best to graft about half the branches the first year and the second half the next. Start with the upper center limbs the first year. The best time to topwork is just as growth begins in the spring; however, it can be done several weeks earlier or later.
A. Stock may be prepared with a single cut, left, or a double cut.
B. Cut scion to form a shoulder.
C. For single cut, left, insert scion under bark, making a tight fit. For double cut, use small nails to secure scions.
Bark graft (veneer graft)
Bark grafting (Figure 3) is relatively easy and requires no special tools. It is similar to cleft grafting and may be performed on branches ranging from 1 inch to several inches in diameter.
- Stock preparation
The branch or trunk is cut off at a right angle in the same manner as described for cleft grafting. The bark graft can be made only when the bark slips or easily separates from the wood. This usually is in early spring as growth begins.
Several techniques can be used on the stock for the bark graft (Figure 3a):
- Make a slit in the bark about 3/4 inch long.
- Make two slits in the bark separated by the width of the scion.
- Scion preparation
The scions should be dormant, so gather deciduous plants before that time and keep them wrapped in plastic under refrigeration to prevent drying.
The scion should be 4 to 5 inches long with two to three buds. Prepare the base of the scion by cutting inward 1-1/2 to 2 inches from the base then downward, forming a shoulder and long, smooth cut (Figure 3b). The long cut should extend about one-third through the twig, keeping its base strong enough to insert but not too thick. On the side opposite the long cut, make a short cut to give the base of the scion a wedge shape for easier insertion.
- Inserting the scion
A knife may be used to lift the bark at the top of the slit but may not always be necessary. Push the scion down and center it in the slit or between both slits if the double slit method is used. Insert the scion until the shoulder rests on the stub (Figure 3c). If the scion is large enough, one or two small nails may be used to tighten the scion to the stock. Some prefer to use electrical tape or masking tape to pull the surfaces tight. In some cases, the bark may not split or tear and nailing or wrapping is not necessary. In all cases, the graft should be thoroughly protected with wax over all open surfaces after it is completed.
A. Cut scion to form a short, smooth edge.
B. Make a slanting cut into the stock.
C. Insert scion so that cuts on thicker side match the cambium of the stock.
D. Cut off the top of the stock only after growth begins.
Side graft, stub graft
The side graft is relatively simple and is suitable for plants that are too large for a whip graft but not large enough for cleft or bark grafts (Figure 4). The plant or branch that will serve as the stock should be between 1 and 2 inches in diameter. The material for the scion should be about 1/4 inch in diameter.
- Preparing the scion
The scion should contain two to three buds and be about 3 inches long. Make a wedge at the end of the scion similar to that made for cleft grafting, but it should be shorter (Figure 4a). Make one side slightly thicker than the other. It is not necessary to make the cuts more than 1 inch long. As with all grafting cuts, they must be made straight and smooth, with a single movement of a sharp knife.
- Preparing the understock
Select a smooth area near the base. Use a sharp knife to make a slanting cut into the stock cutting (Figure 4b). The cut should angle downward and extend about halfway through the branch.
- Inserting the scion
Pull the upper part of the stock back to open the cut. Insert the scion into the open cut with the slightly thicker side lying along the cambium. Set the scion at a slight angle to give maximum contact (Figure 4c). When the top is released, the scion should be held in place, so no tacking or wrapping is necessary. Some people prefer to tack or wrap the union. Do this carefully, so the cambial alignment is not disturbed. The stock or stock branch should then be cut off 5 to 6 inches beyond the graft. Also, remove any lateral branches on the stub that might crowd the graft as it begins to grow. Wax the graft carefully so that all cut surfaces are covered. The tip of the scion, as well as any open wounds made by removing lateral twigs on the branch, should also be waxed. After several weeks, when the scion has started growth, the remainder of the stock should be carefully cut closer to the graft, and the new cut should be waxed (Figure 4d).
Scion wood should always be dormant. Scion wood should be made from previous season’s growth and have a diameter of 1/4 to 3/8 inch. Store the scion in moist sphagnum moss, sand or a plastic bag in a cool place. It must be kept moist and cool until used. After the cuts are made, scions must be inserted immediately, or cuts should be kept moist until used.
Scion wood should be made of twig sections with two to three buds each. Discard the tip of scion wood and recut the base before grafting.
The best time for grafting is in the spring just as growth starts. When necessary, grafting can start several weeks before growth is expected and can continue a few weeks after growth has started, if you have dormant scion wood in storage and if weather is not exceptionally warm.
The stock and scion must have cambial contact for union and growth to take place. All cut surfaces must be covered and kept covered with grafting wax until complete healing has occurred. In a few techniques, alternate methods for maintaining moisture in the union are used. But if you are grafting only a few plants, you will find waxing the graft most satisfactory.
After the graft has taken and growth has started, cut off any side shoots or competing twigs that would shade or compete with the development of the new graft.
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Audio clip 1
The banana graft can be used for slightly older plants where stock and scion are about the same size. The stock is peeled as shown and the wood is cut.
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Audio clip 2
Here the wood has been removed from the stock and is ready to receive the scion, which is being prepared.
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Audio clip 3
Apple plants joined by whip-and-tongue grafting.
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Audio clip 4
After the stock and scion are fitted together, they are wrapped to keep the union tight and moist. After healing through the winter, they will be ready for the field by spring.
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Audio clip 5
For a cleft graft, where the stub is split, two scions are normally used.
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Audio clip 6
This scion of pecan being prepared for bark grafting will be fit on a section of the 1-1/2-inch pecan seedling rootstock that has been cleared of bark.
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Audio clip 7
After completing the grafting process, promptly cover the union to keep the graft cool and moist.
Whip and tongue graft
Download whip and tongue graft doc
The ‘whip and tongue’ graft is probably the most widely adopted method of bench grafting. Ideally choose rootstock and scion material of the same thickness as this maximises the chance of cambial contact all the way around. However, if your scion wood is thinner than your rootstock you can adjust the graft slightly to accommodate this.
The cambium layer, the slimy layer between the wood and bark, is where active growth occurs. Joining the cambium layers of the root and scion is crucial to the success of the graft. In whip and tongue grafting this is done when corresponding cuts through rootstock and scion material are joined end to end and then bound. The interlocking ‘tongues’ add structural support to the join as the cambium layers heal and fuse together, as well giving a larger surface area of cambial contact.
This graft is best done in late winter or early spring and it is extremely important that the scion wood is dormant, with no signs of growth. Dormant scions stored in an airtight container or bag in the fridge can be grafted later in the year onto actively growing rootstocks. This is useful for the stone fruits such as plums and cherries because they need more warmth to start the healing and bonding process. You could also consider hot-piping these.
Some rootstocks have compatability issues, in particular pears on Quince A or C. These will need an inter-stock, also known as a stem-builder, of a variety known to be compatible (Comice is frequently used).
Before starting, it is worth practicing on some spare pieces of wood to ‘get your hand in’ and increase your confidence. Hawthorn makes good practice wood if you are short of scion material.
Be careful not to touch the cut surface of either your scion or rootstock, as oils from your skin can interfere with the healing of the graft.
You will need
- Scion wood of your chosen variety – see scion selection guide
- Grafting knife or similar sharp knife
- Grafting tape – florist tape or strips of freezer bag will do if you can’t get hold of grafting tape
- Grafting wax – candle wax mixed with a little petroleum jelly to reduce melting point works
- Tree label
- Waterproof marker pen
- Make a slanting cut through the scion wood with a sharp grafting knife. Aim to create a flat oval cut face between about one and two inches long. This cut should ideally be done in one go, as this slice needs to be smooth and flat. Longer cuts will give better support, but are more difficult to get completely flat, as well as to bind tight along the length of it.
The best way to make this cut is by holding the knife in your dominant hand, the wood in the other, and cut with a pulling motion parallel across your chest and away from the hand holding the wood. Try to make this cut with a single slicing motion using the length of your blade. Using a straight edge, like the back of your grafting knife, you can assess whether your cut is roughly straight, if not then try doing again. It is worth getting this bit right.
- Make another cut downwards into the scion wood, about one third of the way from the top of the cut face, about half an inch deep. This is a dangerous and difficult cut, as you are often cutting towards your hand that is holding the work. To minimise the risk of damage, place the outside edge your cutting-hand thumb over the end of the thumb of the hand holding the material to ‘lock’ them in a figure ‘T’. This will give you more control and reduce the chance of the knife slipping. This creates one of the ‘tongues’ that will interlock and hold the join fast.
- Make a corresponding slanting cut in your rootstock. Match up these cut surfaces, to check that they are the right length, and that if held together the cambium layers meet. Make any adjustments to your cuts if necessary. A small gap is acceptable as the binding will pull the two pieces together.
- Make a matching tongue cut of equal depth in the scion wood. Line the cuts up, and slide them together, making sure to interlock the tongues. Check again that the cambium layer of each is in contact with the other. This is crucial to the success of the graft.
- Wrap the graft tightly with grafting tape or something similar. This helps keep the cut sides pressed firmly together, and also reduces the loss of moisture from the cuts. Tie off with a half hitch knot unless you are using self-adhesive grafting tape. Alternatively you can tie your graft together with strips of freezer bag, florist tape, string or even elastic bands, but for the latter two make sure to cover the grafted area with grafting wax afterwards to make it watertight.
- Cut the scion wood at a slanting angle away from the third good bud above the graft. Cover this cut surface with grafting wax to seal it. Make sure the wax isn’t too hot otherwise you can damage the top bud, just melted will do.
- Label immediately with the variety, the rootstock, and the date of grafting. It is all too easy to forget what you have by the summer.
- Dig your tree in to a pot of soil or a bed in a sheltered position out of the sun while the graft heal.
- The graft needs to heal before your new tree will start to grow. This can take anywhere from a couple of weeks to a couple of months, depending on the conditions. Once the top bud has grown an inch or so you can be happy your graft has taken and you can move the plant into a sunnier location.
- Once it is clear that the graft has successfully taken cut off all but the strongest shoot, usually the top one, as well as any growth below the graft. Remove any other shoots for the first few years of growth.
- Carefully remove the tape around mid-summer. If it has taken the graft should be healed and the young tree growing. If you wait too long to remove the tape, you can strangle and kill the graft.
- Grafts that have taken and grown over the summer can be planted over the winter, or grown on for another year first. If you plant them out the winter after grafting, make sure to clear the area of plants as these will compete for water and may grow to out-shade your young tree or create a microhabitat that is too humid. If you grow them on for another year before planting out, pot up after the first year to refresh the soil and give the roots space to develop outward rather than forming a tight ball or winding around the container base.
Modified whip and tongue graft
It is best to do your whip and tongue graft using scion wood that is the same diameter as your rootstock, however this is not always possible as sometimes you have larger rootstocks than scions. This is absolutely fine as you can modify the cuts of your whip and tongue graft to accommodate the difference.
Start by cutting the wood of the smaller diameter as in step 1. Normally this will be the scion wood. Use this as a template for the size and shape of the cut to your larger piece. Cut away only the side rather than going all the way through so that the cut surface is the same size as the first piece. Make sure that you cut deep enough to reach the cambium layer because as with any graft, it is the contact between the cambium layers that heals and creates the union. Once you are happy that the two cut surfaces match in size and shape, carefully put the tongue cuts in, interlock these tongue cuts and bind as you would with a standard whip and tongue graft.
Download a Word version of this whip and tongue graft guide
Grafting is also performed to produce dwarf plants that are true to their variety. A less desirable plant can be changed by grafting a more desirable species to the rootstock.
Multiple varieties can be grafted to the same rootstock to produce a novelty tree that will produce several different fruits on the same tree. Most roses are also a product of grafting to a different rootstock.
Grafting can be performed either through a stem cutting graft to the rootstock or through budding, which is a process where a bud, but not an entire stem, is grafted. This is often the preferred method for apple trees, but is also used with other fruits as well. Wax is used to cover the grafted area and then it is wrapped with growing tape to protect it during the healing period.
A number of different plants can serve as the rootstock, but often hardy flowering quince is preferred because of its tolerance in northern climates. Grafting to a hardy rootstock enables plants to grow in a colder climate without suffering root freeze.
A plant produced through grafting can usually be spotted by a lump or ball-like growth at the base of the stem where it attaches to the rootstock. The grafted point should never be buried, or the rootstock will grow instead of the grafted upper portion of the plant.
How to Graft Pine Trees
pine cone on a pine tree image by MAXFX from Fotolia.com
Most trees that are grafted are hybrid trees; they do not reproduce seedlings that are exactly the same as their parent trees. But there are a handful of reasons for grafting a pine tree. Reasons for grafting pine trees range from filling in bare spots on ornamental or Christmas trees to creating trees that are more disease-resistant or that have accelerated breeding cycles. Several different grafts are suitable for grafting pine trees.
Cut a scion from a pine tree that is less than 5 years old.
Position the pruning shears at a spot on a branch that is 6 inches from the end of the limb.
Cut the scion away from the limb by making a slice crosswise to the limb.
Place the scion in a plastic freezer bag with 1 tbsp. of water. Put the bag in a refrigerator at 40 degrees Fahrenheit. Store the scion through the winter.
Graft the scion onto a pine tree’s trunk, known as the rootstock, in early spring, using one of the methods below.
Cut the bottom of the scion so that the cut end makes an angle that is approximately 1-½ inches long.
Cut a tongue into the scion about halfway up the slice made in Step 1, using a draw cut, which is a single cut with a grafting knife. Carefully control the cut so that the branch does not split under the pressure. Pull the blade down the center of the branch to a point that is even with the start of the cut in Step 1.
Make an identical set of cuts into the rootstock tree’s trunk or branch. Make cuts in the rootstock that mirror the cuts in the scion so that the two pieces fit together like pieces of a puzzle. The trunk or branch of the rootstock should be the same size as the scion branch.
Press the scion onto the rootstock. Make sure that the bark layer of the scion and rootstock touch. Bind the two parts together with polyethylene grafting tape.
Remove the tape in a few weeks when the scion and rootstock heal together.
Cut the end of the scion to a blunt point in which one side of the point is thicker than the other.
Remove a thick branch or the top of a pine tree with a saw.
Create a cleft in the exposed rootstock cut with a clefting chisel. Do not allow the bark to split at the ends of the cleft.
Slip the blunt point of the scion into the cleft. Ensure that the bark of the rootstock and scion touch.
Cover the union between the scion and rootstock with asphalt water emulsion compound.
Cut the end of the scion to a blunt point in which one side of the point is thicker than the other.
Select a smooth portion of a rootstock branch located at least a foot from the trunk of the pine tree.
Make a slanting cut at an angle that extends almost to the core of the tree branch.
Bend the rootstock branch back and insert the scion limb into the cut. Ensure that the bark of the scion and rootstock limb touch. Wrap the bark with polyethylene grafting tape to secure the union and keep it from drying until the union heals.
Remove the tape when the union heals. Remove the rootstock limb at a point beyond the graft.
Is root grafting a positive, cooperative behavior in trees?
Natural root grafting between individuals has been observed in over 150 species of plants around the world. However, while much is known about benefits of merging stem tissues (primarily from horticultural practices), little is known about why plants may merge, or graft, their root tissues with one another.
Emilie Tarroux and Annie DesRochers, from the Université du Québec in Abitibi-Témiscamingue, Canada, were interested in determining if root grafting conferred any advantages to individual jack pine (Pinus banksiana) trees. Although the joining of tree root systems can confer advantages such as increased wind stability and sharing of resources e.g., water, photosynthates, or nutrients, Tarroux and DesRochers are the first to show how root grafting affects the growth of trees. They published their findings in the June issue of the American Journal of Botany.
“Trees, even seed-regenerated ones like jack pine, are not independent individuals,” DesRochers commented, “and may directly affect growth of their neighbors by forming root grafts.”
After felling select jack pine trees in three natural stands and three plantations, Tarroux and DesRochers hydraulically excavated their root systems using a high-pressure water spray to determine if the trees had root grafts. They then aged the trees, roots, and grafts by counting and cross-dating their respective growth rings.
Interestingly, the authors found that radial growth patterns differed between jack pine trees growing naturally versus those grown in plantations. In the natural stands, there were more root grafts per individual tree than in the plantations, and growth of these trees slowed down when they were forming root grafts with other trees, but then resumed or gradually increased their rate of growth once the root graft was established. In contrast, root grafting in the evenly spaced plantations seemed to have less of an effect on growth rates.
The authors also discovered that trees which would later form root grafts tended to have better growth rates compared with trees that did not form root grafts, even prior to graft formation. Individuals may need to become large enough in order to have enough energy to complete a root graft, or so their root systems are able to come into contact with those of other trees. Conversely, smaller, weaker trees may lack energy to form root grafts, or they may not have very extensive root systems.
So what are some of the advantages of joining root systems with another tree?
“Root grafting could give an evolutionary advantage to the species,” said DesRochers. “For example, it could allow well-located trees to support trees that grow in drier or poorer environments. This has been known for herbaceous species that propagate vegetatively, but has rarely been addressed in trees.”
Indeed, if the larger trees facilitated acquisition of resources among conspecifics in the stand, they could maintain stand integrity; supplying carbohydrates to suppressed trees could deter tree death that would create gaps in the stand which would then allow other species to invade. Such root grafting behavior could be viewed as the formation of a communal root system, enhancing conspecific growth within the stand. This challenges the typical competition outlook, and could be interpreted as an intraspecific cooperative behavior that maintains stand integrity.
“Interestingly, we also found a couple of root grafts between jack pine and black spruce during the excavation of the sites,” noted DesRochers. “Mentions of interspecific grafts are absent from the literature and makes us question the evolutionary significance of these grafts. Unfortunately, we haven’t found any more since — and we have searched!.”
“The next step in our research is to study the ecological significance of these root grafts,” concludes DesRochers. “Among other things, we’d like to see how much, how far, and what substances (photosynthates, water, hormones, etc.) are shared between interconnected trees.”