Arborists and horticulturists toss the term around loosely. Grafting. What is it, and why do we need to do it? How do we do it? There are lots of answers to these questions, and we intend to answer a few of them. Along the way, we hope to give you some skills that will make your garden and orchard a more productive space.
So, why do fruit trees need to be grafted? Grafting is the technique of joining the tissues of plants in such a way that they continue their growth. Fruit trees need grafting for several reasons, some of which include:
- Dwarfing of the variety
- Easy Propagation
- Hardiness
- Disease/Pest resistance
- Genetic Consistency
There are many other reasons that fruit trees need grafting, but these are the reasons most cited by arborists, orchard managers, and home gardeners for grafting fruit trees. The techniques used are well known and documented and, for the home or hobby gardener, not hard to learn and practice.
What is Grafting?
Grafting is an ancient means of protecting and reproducing trees that have proven to have some unique attribute worth saving. The tree may exhibit resistance to certain diseases or pests. The rootstock of a tree may be more suitable for a particular soil type than the rootstock of the tree we want to cultivate. We may want to do something entirely different by producing a tree that will bear several different kinds of fruit
Grafting is useful for conserving or continuing a plant that exhibits some special characteristics. It could be a more flavorful fruit or a higher cold tolerance than usual. The beauty of grafting is that the grafted plant is a clone, a genetic copy of the original plant, and carries all those traits forward.
All these things are possible, and many more, by understanding grafting and developing some skills in the techniques of grafting woody plants, especially trees.
Put simply, grafting is the process of taking a cutting from one plant and joining it another plant so that the cutting and the host plant continue to grow and flourish. There are some terms that we will use as we discuss grafting.
- Rootstock – The rootstock is the lower part of the plant. Grafting done into an existing tree has exciting possibilities, as we will discuss later. You don’t need to cut the tree down to a stump to do a successful graft to the tree.
- Scion – When we refer to the scion, we will be talking about the new plant placed into the rootstock. Another term we may use for this is cutting.
- Cambium – Cambium is the internal woody parts of a plant that makes up the vascular system through which liquids and nutrients disperse through the plant system.
Grafting is that simple. The concept is to take a cutting or scion from one tree and graft it onto another tree so that the two join and continue to grow. The reasons for grafting are numerous, and we are about to learn more about why fruit trees need grafting.
Why Graft Fruit Trees?
Many grafting authorities cite a long list of reasons for performing grafting techniques on fruit trees. Some of these reasons are for research purposes or for hybridizing certain species to save or increase favorable traits in the plant. For the home or hobby gardener, there are some very basic reasons that you should consider grafting.
Dwarfing
If you garden on a limited space and want to have a few fruit trees, you may consider grafting your favorite varieties onto a dwarf variety rootstock. Grafting on to dwarf rootstock is a technique used by apple growers to increase the yield from their apple orchards.
Propagation
Some trees are difficult to start from seeds. Even if you manage to get a seedling started, some varieties take years to reach the point they will start producing fruit. Grafting can shorten the time for trees to produce fruit by eliminating the juvenile stage of the tree growth cycle.
Hardiness
Many fruit tree varieties are subject to soil conditions that make it impossible to grow a variety. Grafting the desired variety onto a rootstock that is known to flourish in the soil conditions present in the garden makes it possible to grow the desired variety in soil conditions that may not be supportive of the original variety.
Disease/Pest Resistance
Some areas contain soil-borne diseases and pests that make it impossible to get certain varieties of trees to grow. Grafting a variety of trees to a rootstock that is known to be resistant to these local pests or diseases Is a common practice. An example of this is the grafting of grape scions onto rootstock that is known to be resistant to phylloxera.
Genetic Consistency
Many fruit trees, especially hybrid varieties, are notorious for being genetically variable. Trees raised from seeds from these hybridized varieties may or may not carry on the desired traits and may even revert to producing fruit more characteristic of one of the original trees used to create the hybrid. Grafting is essentially a means of cloning the original plant and ensuring that the genetics of the plant reproduce consistently.
Grafting is used for many other purposes as well. Repairing trees by performing grafting is common among arborists specializing in damaged tree repair. Many orchard owners who want to change the cultivar in their orchard may graft new varieties onto the existing rootstock to get the orchard into production faster. Some fruit trees require a pollen source from another variety to fruit successfully. Grafting this pollen source into the tree makes the tree self-pollinating.
How to Graft Fruit Trees
Grafting is not difficult in most cases. However, there are some tools you need and some knowledge that will get you on your way to grafting like a pro. Like any skill, there is a learning curve that you must traverse to become skilled.
What You Need to Produce a Successful Graft
There are several factors to consider before grafting two plants.
Plant Compatibility
The first is the compatibility of the plants. When you graft plants, the plants must connect tissues. If the plants are not at least similar in their tissue structures, the graft won’t take. Ideally, the plants you are grafting will be as close genetically as possible. Grafting two entirely different families of plants is next to impossible.
Timing
Timing is essential in grafting as well. For the graft to complete, both parts of the graft must be at a stage when they can produce wound-healing responses such as callus. Ideally, the scion should be dormant when making the graft to prevent the scion from producing buds, which can damage the grafting site.
- Take the scion portion of the graft when the contributing plant is dormant. Cutting during dormancy will prevent the scion from trying to bud after the cutting. Late winter is a good time to take scions. Scions can be stored by wrapping them in damp paper towels and putting them in an airtight container. Poly Ziplock bags work well for this. Store the scions in a refrigerator between 33- and 40-degrees Fahrenheit.
- Grafting to the rootstock is usually performed during the growing season when the bark of the rootstock slips. This condition is easily recognizable when the bark is readily detached from the underlying wood easily without tearing or breaking.
Cutting and Protection
Cuts made for grafting must be smooth and uniform with no gouges, irregular surfaces, or tears. The success of grafting depends on the cambium of the scion and rootstock mating and joining during the healing process.
Protecting the graft site is an important part of grafting skills. Water is the big enemy as it can invade the graft and cause rot or other damage. Depending on the size of the scion, you may need to provide additional structural support at the graft site.
The Proper Tools and Habits
Perhaps the most important tools required for good grafting are the cutting tools. Grafts are made using special knives and grafting tools. The choices are many, and your personal preference is the key. Whichever type of tool you choose, keep it sharp and clean.
Cleanliness is imperative. Remember that you are creating open wounds on two plants. It is easy to transmit diseases between plants with dirty tools. You should make it a practice to disinfect your cutting tools after each use and when you move between plants.
It is a good idea to keep a supply of crafting materials on hand. You should have a collection of tying and support materials, as well as sealing material. These come in a variety of forms, from tapes to waxes.
The Many How To’s of Grafting
There are almost as many ways to make grafts on fruit trees as there are varieties of trees. We can’t cover them all. You should explore the possibilities and settle on two or three methods and become familiar and practiced at those methods, then expand your repertoire with other methods. We have picked some of the most popular and easiest to learn methods of grafting.
Wedge Grafting
Wedge grafting grafts a new scion onto old rootstock and is a great technique for changing the cultivar or variety in an orchard. Using established rootstock and scions from known trees can quickly re-establish a producing orchard in a much shorter time.
Late winter is the usual time for performing wedge grafting on trees. Both the scion and the rootstock should be dormant, with no growth occurring on either side.
- Prepare the scion by selecting a specimen that is the same diameter or just smaller than the diameter of the rootstock. Select a specimen and cut a length sufficient to capture at least three buds. Trim the lower end of the specimen to form a tapered wedge shape.
- Prune the rootstock to at least 6 inches above the ground. Prune the rootstock flat and smooth across the top. Make sure your cutting tool is sharp and clean and try to avoid any splintering or tearing of the bark or outer portions of the rootstock trunk.
- Split the flat pruned top surface of the rootstock to the same length as the wedge you prepared on the scion. This step is very important so that the two surfaces on the scion and the rootstock mate as tightly as possible without any exposed inner plant material on either part.
- Insert the scion wedge into the split in the rootstock. Make sure the surfaces mate well. They two surfaces must be in close contact with one another to have proper healing. Once you are sure that the surfaces are tight, tape the graft securely.
- Start wrapping the tape from a few inches below the graft and continue upwards, making sure that you overlap the tape generously. Wrapping from the bottom helps keep excess moisture from seeping into the grafted joint. End the wrap a few inches above the graft.
- Wedge grafted plants should be supported to protect the graft from structural stress. Use a stake that extends up past the graft. Some experts suggest making the support stake a few inches taller than the total height of the plant with the graft to provide a roost for birds. The extra height will encourage birds to roost on the stake and keep the weight of the bird from damaging the graft.
Whip or Spliced Graft
The whip graft is probably the easiest of the graft techniques to make. Whip grafting is probably one of the oldest methods of grafting trees. It is commonly used on apple, pear, and pecan trees in orchards today. The principal tool used in whip grafting is a sharp pruning knife.
The scion and the rootstock graft site should be as close to the same diameter as possible. Keeping the diameters close matched makes mating the scion and the rootstock much easier and leaves no exposed inner plant material for insects or disease to attack.
- Make the cuts on both the scion and root stock by slicing upwards through the plant material cleanly. The sharpness of your pruning knife is critical, as is its cleanliness. The cut must be flat, smooth, and without a ragged or torn edge. The angle of the slices must be as close to the same as possible, as must the length. Experts suggest that the length of the slice be close to twice the diameter of the scion and rootstock.
- To make the graft, place the two cut faces together so that they mate flat. Using twine or tape, wrap the graft, starting below the graft site, and work your way back up the graft. The wrapping must be tight enough to hold the grafted surfaces securely together, but not so tight as to damage the bark of the tree.
- If the scion is slightly smaller than the rootstock diameter, offset the scion to the edge of the rootstock rather than center it. Offsetting the scion on the rootstock will promote a better match between the tissues and promote faster healing of the graft.
Whip and Tongue Graft
A variation on the whip graft, the basic concept is the same. The scion and rootstock should be as near as possible to the same diameter. The initial cuts are made the same way and at the same angles. Remember to use a sharp, clean implement to make your cuts
- Once you complete the initial cuts, make a second on the scion and the rootstock. This cut should be into the flat side of the angle but starting at about the mid-point of the flat side of the angle. The second cut should angle into the center of the rootstock and scion, leaving a forked joint.
- This forked joint doubles the mating surface and increases the structural stability of the graft. The whip and tongue graft is a bit more difficult to execute than the whip graft since the second cuts must be precise so that they can mate together seamlessly when the graft is complete.
- Making the graft requires that the two cuts slip together so that the three cut surfaces meet firmly and flatly. With the graft firmly fitted together, wrap the graft joint with twine or tape starting below the joint and working your way up over the joint.
- If using tape, make sure the tape overlaps. Keep the wrapping tight enough to stabilize the grafted joint, but not so tight as to inhibit the healing growth that will occur.
Four-Flap Graft
The four-flap graft is a more complicated type of graft than the whip graft or whip and tongue graft. However, even the most novice grafter in the garden should have this graft in their grating kit. It is a perfect method of grafting smaller trees up to one inch in diameter
In preparing for this grafting technique, selecting your scion and rootstock is an important step. The two should be as close to the same diameter as possible, or the scion is slightly larger than the rootstock. Using the four-flap graft requires a bit of pre-planning.
The scions should be collected from the contributing trees while still dormant. Late February or early March are perfect times in most growing zones. The key is to make sure the trees are dormant and haven’t started to bud.
The best options for scion wood are no larger than 3/4 inch in diameter. The cutting should be healthy one-year-old wood and should have well-developed buds along the length of the scion. After making your cuttings, wrap them in a moist paper towel and place them in an airtight container. Plastic kitchen bags are great for storing scions. Keep the scions in the refrigerator until time to make the grafts.
The best time to make four-flap grafts is when the rootstock is actively growing. April to mid-May is a perfect time in most climates. One key to knowing a good time to graft using this technique is to test for wood slippage on the rootstock. If the tree is ready, the bark will lift or “slip” easily from the tree when cut.
- Prepare the rootstock by making a flat straight cut across the trunk. You may leave one or two lateral branches below the cut, but they should be pruned back to six inches. If you have problems with cattle or other grazing animals, make the graft cut as much as 8 feet above the ground. More reasonably, prepare the graft site on the rootstock at a comfortable working height.
- At the top of the rootstock, make four cuts in the bark of the tree vertically, starting about 2 inches below the flat cut surface. Space the cuts equally around the trunk of the rootstock. Carefully peel the bark down, exposing the inner wood material and leaving the flaps attached.
- Now do the same procedure with the scion. Choose a scion approximately the same diameter or slightly larger than the diameter of the roots stock and peels the bark up the scion from the horizontal cut. Leave the flaps attached.
- Using a pair of sharp, clean pruning shears, cut the inner wood of both the rootstock and scion just above the point the bark flaps are attached. This cut must be smooth and flat so that surfaces will have full contact with joined.
- Put the scion on top of the rootstock, making sure that the surfaces have as much contact area as possible. Pull the four flaps of the rootstock up over the joint and secure them with a bit of florist tape. Work the flaps on the scion between the flaps on the rootstock and pull them down, securing them below the graft with florist tape.
- Begin below the flaps of the scion on the rootstock and wrap upwards with floral tape or some other material that will allow expansion of the graft as it heals but will protect the graft from insects, disease, and excess moisture.
Saddle Graft
The saddle graft is another form of wedge grafting. It is best when the scion and rootstock are nearly identical in diameter. Like most grafts, the scions should be taken when the contributing plant is dormant and stored properly.
- Prepare the scion for grafting by cutting upwards through the bark and into the woody core of the plant. The upward cut should move half the diameter of the plant and a corresponding upward cut made on the opposite side. The result should be an inverted V shape in the lower part of the scion.
- The rootstock cut should be the inverse of the cut on the scion, forming a wedge shape that fits into the inverted V shape, or saddle, on the scion. The two surfaces should fit together tightly to maximize the contact area of the woody core of the plants.
- Starting below the graft, wrap the join with twine or florists tape to above the grafted joint. The saddle graft is an extremely secure graft when made properly but, on larger grafts, supporting structures may be necessary to reinforce the graft until healing is well underway.
Unusual Grafting Ideas
Don’t let the concept of grafting keep you from thinking outside the box. Grafting can create some unusual and spectacular additions to your garden and orchard. If the plants are related, the grafting can be successful. Grafting doesn’t have to be just for propagation.
One example of this is the “salad tree.” Imagine having a citrus tree in your garden, greenhouse, or sun porch that produces several different kinds of fruits on the same tree. It is possible to graft several different types of citrus onto a single rootstock resulting in a single tree that bears limes, lemons, grapefruit, and oranges.
The same process works with apple trees. Grafting different varieties of apple trees to a single roots stock can produce a single tree that is self-pollinating and produces an apple smorgasbord. Add pears to the mix for more variety.
If fruit trees are not your passion, don’t despair. Grafting will work on flowering trees and even roses. Grafting multiple varieties of roses can result in a stunning display of colors and styles of rose on one plant. Imagine a tree that flowers in multiple colors or even different shades of the same color. Grafting can be as artistic as it is horticultural.
A Few Tips for Getting Started
It’s easy to get started grafting. All you need is some contributing plants for your scions, some rootstock, and a few simple tools. Our suggestions for a budding grafter (pun intended) are:
- A good pruning knife and sharpener;
- A pair of sharp pruning shears;
- Florists tape;
- Garden twine;
- Plastic bags; and
- Some time
When you do start grafting, keep a few things in mind for your best chances of success.
- Choose the strongest and healthiest parts of the plant from which to take your scions
- Prepare them carefully and store them correctly
- Keep your tools sharp and clean. Disinfect them regularly.
- Make your grafts when the bark slips on your rootstocks.
- Don’t expect 100 percent success. Even the best grafters suffer losses.
The more you try, the more you will learn. Get into your garden and get started!