- The Science of Grafted Fruit Trees
- Graft Failure
- Normal Bulging at Graft Union
- Grafting Fruit Trees Step-by-Step by Z Grafting – YouTube Video
- Citrus Budwood from a Disease-free Source
- Sterilizing Grafting Tools
- Grafting the Valentine Pummelo Hybrid
- Rootstock Suckers
- Grafting a Large Diameter Scion to a Smaller Diameter Rootstock
- Cutting the Top off of the Rootstock
- Cutting a Strip in the Rootstock
- Cutting the Scion
- Fitting the Scion and Rootstock Together
- Cambium Contact
- Wrapping with Parafilm-M
- Wrapping with a Rubber Band
- Wrapping with a Second Layer of Parafilm
- Grafting a Backup Scion
- Citrus Z-graft Growing
- Pruning off the Original Variety
- Picking the Winning Graft
- Healing of the Winning Graft
- Staking the Tree
- Removing a Rootstock Sprout
- Finished Valentine Pummelo Tree
- Save Trees by Sharing
- Resources for Californians
- California Law Regarding Citrus Propagation
- Espalier Training Question: Can I Graft Two Living Trees Together? What Will Happen?
- Turn Your Favorite Tree Into Many, by Grafting
The Science of Grafted Fruit Trees
There are vast differences between grafted fruit trees and seed-grown fruit trees. Learn why you don’t get true-to-name fruit by planting seeds.
Have you ever wondered why you can’t always grow a true-to-name fruit tree from planting seeds? Folks often ask if it’s possible to take the seeds from an apple, plant them, and grow trees that yield the same exact type of apples the seeds came from.
Unfortunately, for most fruit trees*, this isn’t quite how it works. To explain, we’ll start by addressing the history contained in seeds and why it’s more reliable to plant and grow grafted fruit trees.
*There are exceptions that tend to have very little variation even as seed-grown trees, like pawpaw seedlings and certain types of citrus.
Reproduction in Fruit Trees
We’ll use apple trees for example here. Most apple trees are not self-fertile. This means they need another different apple tree blooming nearby (at the same time) to pollinate the blossoms that in turn become the fruit.
So, if you had a Honeycrisp apple tree, you would need a different apple variety, like a Golden Delicious apple tree, to pollinate it. From one tree to the other, the male flower parts’ genetic material pollinates the female parts of the flowers (with the help of bees, wind, etc.). The end result is fruit development in both mature apple trees.
History is Contained in Seeds
This cross-pollination is sexual reproduction in fruit trees. Even if a fruit-tree variety is considered to be self-pollinating, it is still receptive of other pollen — and the seeds of its fruit end up with all the history from past generations of both parent trees. The results of cross-pollination occur in the seeds, not the fruit. This is why cross-pollination can occur in your fruit tree’s flowers and not affect the color or appearance of the tree’s developing fruit.
The fruit is merely a vessel for the seeds. The seeds are what carry a history of traits from the parent tree and its pollination partner(s).
That’s a lot of potential, but it’s also unpredictable. If you were to plant the seed from a Honeycrisp apple, the resulting apple tree and its future fruit may display characteristics from anywhere in its lineage. The tree or its fruit may be similar to Honeycrisp or they may be throwbacks from somewhere in its genetic history, but – because they came from seed – they will not become a true Honeycrisp apple tree or true Honeycrisp apples.
Grafting for Consistency
One dependable way to ensure that the desired characteristics are maintained in subsequent fruit trees is through grafting. Grafting involves taking a scion or bud chip cut from the desired parent tree (for example, a Granny Smith apple tree) and physically placing it onto a compatible rootstock. The variety and the rootstock are calloused, or grown together, as the tree heals. All suckers are removed from the rootstock, and the Granny Smith scion is allowed to grow into the new tree, thus maintaining its Granny Smith identity. This process is called “asexual reproduction”. Since only one parent/variety is involved in this process, the grafted tree will be true-to-name — and a true-to-name tree bears true-to-name fruit.
Most of Stark Bro’s trees are either propagated through grafting — by joining a scion and rootstock together — or through budding. Budding involves placing a single vegetative bud into the side of the rootstock and wrapping it with cellophane tape until it heals together. The results of grafting and budding are the same: a true-to-name tree.
A grafted tree is consistent and has a reliable history of characteristics. It has a track record:
- It blooms at a certain time.
- It bears fruit at a certain time.
- It has predictable traits like disease-resistance or cold-hardiness.
- Its fruit can be expected to be a certain size, quality, and variety.
See the consistency in size and shape of these grafted fruit trees?
With this in mind, I will always recommend you plant trees that were propagated through grafting or budding methods. It’s worth the investment to know exactly what you’re getting!
— Elmer Kidd, Stark Bro’s Chief Production Officer (retired)
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- Frequently Asked Questions
Graft failure – Credit R. Heflebower
Graft incompatibility, improper technique, or environmental conditions, may cause graft failure. Graft incompatibility is not clearly understood but may be the result of genetic differences between the grafted parts. Abnormalities may develop in the vascular tissue at the graft union. Disease-causing organisms such as viruses or phytoplasmas are other possible cause of incompatibility. Care should be taken to use disease-free plant material when grafting.
The most pronounced symptom of graft failure is a smooth, clean breaking off of a tree at the graft union. This may occur one, two, or many years after the graft is made. Other symptoms of graft failure include general ill health of the tree or shoot dieback. Foliage may yellow in late summer, followed by early leaf drop. Vegetative growth of scion and rootstock may begin or end at different times. There is often a distinct difference in growth rate between scion and rootstock. Overgrowth may occur above, at, or below the graft union and results in a visible difference in the trunk diameters. Suckers can develop from the rootstock. While it is possible for trees to survive with one or more of these symptoms, a combination of many symptoms may result in premature death of the tree. Weakened trees may have to be removed.
Overgrowth may occur above, at, or below the graft union and
results in a visible difference in the trunk diameters.
Normal Bulging at Graft Union
A slight bulging, swelling, or “crook ” in a tree trunk, two to three inches above the soil line, is the result of normal healing at the graft union. Grafting is a method of propagation that joins a scion (upper portion) and rootstock (lower portion) of two similar species of plants. The site where the scion and rootstock meet is called the graft union. Swelling occurs as callus tissue is formed and new vascular cambium tissue develops in the callus bridge area. The graft union should remain above the soil line to prevent the scion from developing roots, losing the influence of the rootstock.
Nurserymen frequently use grafting as an excellent way to propagate plants not easily grown from seed or cuttings, especially cultivated varieties. It allows the grower to produce a saleable plant more quickly. This technique allows nurserymen to select and control desirable plant characteristics such as growth habit, growth rate, size, hardiness, and time required for fruit production.
This step-by-step guide to grafting fruit trees shows how to graft a tree using a very useful technique called the Z-graft.
This step-by-step guide shows how to graft fruit trees such as citrus trees with the Z-graft.
Z-grafting is a scion grafting technique that is very helpful for grafting trees in situations where the scion and rootstock have different diameters. I have found the Z-graft especially useful for grafting citrus trees when the scion diameter is greater than that of the rootstock. It is useful both for grafting new trees and also to add new varieties to established trees.
Grafting Fruit Trees Step-by-Step by Z Grafting – YouTube Video
In addition to this step-by-step grafting guide, I have also made a YouTube video (see below) showing how to graft fruit trees with the Z-graft.
Citrus Budwood from a Disease-free Source
Citrus cuttings have the potential to spread tree-killing diseases. It is often not apparent when a tree is infected with a fatal disease. This makes the source of citrus budwood for grafting very important.
In California where I live, we now have both exotic diseases that kill citrus trees and also the insects that spread the diseases. The situation is so severe that it now against the law in California to graft with cuttings taken from backyard citrus trees. To save our trees from deadly diseases, hobbyists in California no longer swap citrus cuttings with friends. We now instead order our budwood at a nominal cost from the Citrus Clonal Protection Program (CCPP), a program that exists to provide disease-free budwood for the grafting of citrus trees.
The CCPP will ship budwood anywhere in the world where the local government allows it. Many citrus growing regions where CCPP budwood is not allowed have their own disease-free citrus budwood programs. Here I have created a web page that lists some other programs: Citrus Budwood Programs.
The below YouTube video goes through in detail the process of setting up an account and placing a budwood order with CCPP.
Sterilizing Grafting Tools
In order to both maximize the probability that the graft lives and also to prevent the spread of disease from tree to tree, it is important to sterilize grafting tools between grafts. To learn more about sterilizing grafting tools, please see the following link: Sterilizing Grafting Tools.
Grafting the Valentine Pummelo Hybrid
The fruit grafted in this article is the Valentine pummelo hybrid, a delicious fruit created by the citrus breeders at the University of California, Riverside by crossing the Siamese Sweet Pummelo with a hybrid of a mandarin orange and a blood orange.
I had neglected this Cara Cara pigmented navel orange tree after I realized that the previous owners of my house had already planted a Cara Cara tree. Normally I would prune off roostock suckers like these, but since I already had a Cara Cara tree I decided to graft to the roostock suckers to convert this tree into a Valentine Pummelo tree.
Grafting a Large Diameter Scion to a Smaller Diameter Rootstock
Since the diameters of the rootstock suckers were smaller than the diameters of my Valentine Pummelo scions, I decided to graft my tree with the Z-graft. When scion grafting fruit trees I usually prefer a cleft graft or a bark graft, but when the diameter of the budwood that I receive from CCPP is larger than the branch to which I would like to graft, the Z-graft is a good choice.
Cutting the Top off of the Rootstock
The first step is cut off the top of the rootstock sucker at about a 45 degree angle.
Cutting the rootstock.
Cutting a Strip in the Rootstock
The next step is to cut off a small piece of the longer end of the rootstock at a very slight angle. Then I cut a thin strip in the longer end of the rootstock and leave it attached.
Cutting a strip in the roostock.
Cutting the Scion
Next I cut off the bottom of the scion at about a 45 degree angle and cut off a small piece of the longer end. Sometimes scions have an angular shape such as this one does. With some tree grafting techniques this can cause a problem. With the Z-grafting technique I will use the angular shape to my advantage by cutting a thin strip from an angled part of the scion in the next step.
Cutting the scion.
I then cut a strip in the longer end of the scion. In order to make cambium contact with the rootstock, it is important that the width of this strip be less than the diameter of the rootstock.
Cutting a strip in the scion.
Fitting the Scion and Rootstock Together
Next I fit the scion into the rootstock to form the Z.
Inserting the scion into the rootstock.
The cambium of a tree is a thin layer of plant tissue between the bark and the wood. The goal with all grafting techniques is to connect the cambium of the scion to the cambium of the rootstock. Grafting fruit trees with the Z-graft creates many points of contact between the cambium layers of the rootstock and scion. This makes for a successful graft and a strong graft union.
Points of cambium contact are shown by the blue arrows. Two different views of the graft are shown.
Wrapping with Parafilm-M
I wrap the graft union with a product called parafilm-M to seal the graft and hold it in place. For cleft grafting and bark grafting I use a different type of parafilm, but I find that parafilm-M is easier to stretch. I felt it would be easier to keep the cambium layers lined up while wrapping if I used parafilm-M. The disadvantage of parafilm-M is that I had to cut it ahead of time to make strips of the appropriate width. To get a good seal, I gently pull on the parafilm as I wrap it. This makes it stick to itself.
Wrapping the graft with parafilm-M.
Wrapping with a Rubber Band
In order to ensure close contact between the cambium layers and to strengthen the graft while it is healing, I wrap the graft with a rubber band.
Wrapping the graft with a rubber band.
Wrapping with a Second Layer of Parafilm
Next I prune the scion to leave three or four buds and wrap the graft with a second layer of parafilm-M. I wrap starting from the bottom, overlapping as I go up. Overlapping the layers keeps the graft from drying out and will also keep out rainwater. Other than the buds, I completely wrap the scion, including the cut end.
Wrapping the graft with a second layer of parafilm-M
Grafting a Backup Scion
Since there were two rootstock suckers, I grafted two scions so that I would succeed even if one of the grafts failed. The graft that I showed above was my second graft (the backup). I am glad that I grafted the backup scion because I made a mistake on my first graft that is shown below. My mistake was to cut the scion such that the width of the scion was greater than the diameter of the rootstock. Because of this, the cambium layers did not touch on the top part of the Z.
Citrus Z-graft Growing
I moved the tree to a shady area for three weeks for the graft to heal. The second graft began to grow four weeks after I moved the tree back into the sun.
Citrus graft growing.
Pruning off the Original Variety
After the second graft put on a bit of growth I cut off the original variety.
Pruning off the original variety.
Picking the Winning Graft
The below photo shows the consequences of failing to connect the cambium layers at the top of the Z of the first graft. The graft was slow to grow because the cambium layers were only connected on the bottom. I pruned it off because the other graft did much better.
Removing the partially healed first graft.
Healing of the Winning Graft
The winning graft healed well on the top and the bottom of the Z.
Staking the Tree
Next I staked the tree.
Staking the tree
Removing a Rootstock Sprout
By the following spring the tree had put on more growth including a sprout from the rootstock. Rootstock sprouts must be removed before they take over and crowd out the grafted variety.
Removing the rootstock sprout.
Finished Valentine Pummelo Tree
Finished Valentine pummelo tree.
Here is the finished tree ready to plant after a few more months.
Save Trees by Sharing
Please share this article with anyone that you think may be interested in grafting fruit trees. Knowledge of the importance of using a registered disease-free budwood source when grafting citrus will help to prevent the accidental spread of deadly citrus diseases and will save trees.
Resources for Californians
Please visit CaliforniaCitrusThreat.org for more information on how to stop the spread of deadly citrus disease.
California Law Regarding Citrus Propagation
In California, the collection of any citrus propagative materials, including budwood and seeds, from non-registered sources is illegal. Any citrus trees grown or grafted in California must come from source trees registered with either:
- The Citrus Nursery Stock Pest Cleanliness Program, administered by the California Department of Food and Agriculture, or
- The Citrus Clonal Protection Program, located at the University of California at Riverside.
This article was funded by a grant from California’s Citrus Research Board.
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Espalier Training Question: Can I Graft Two Living Trees Together? What Will Happen?
If you look up some of the Bonsai techniques you will see various techniques for grafting two separate plants of the same species , most are done by removing bark carefuly
Doing it as they grow from young plants that are already established is one way .
You are best to decide how far apart your ” fence posts ” will be , then plant the young trees that far apart . Put your post mid way in between the saplings & run the straining wires between the posts without too much tension on them .
Start to train a ” leader branch ” in spring wern things are supple & full of sap . Make them lightly & softly fastened to the the wire guide to the adjacent trunk at the height that they grow or gently use the straining wires as anchors to secure a cord tied lightly to a branch thats at a slightly different height . It’s up to you how you do it , two low leaders off one trunk supplying a tree on either side or only taking one leader off each trunk & taking it to just one sapling at each level .
One interesting way is to use a slow speed battery drill or a sharp hand borer and bore a hole with a wood boring twist drill an inch or so into the trunk the diameter of the leader that you have decided to grow where it will enter the new trunk .
You usually take it off an adjacent tree using grafting wax & self amalgamating rubber tape to seal the hole & keep the leader in place in the new trunk .
A demonstration I saw was where a long leader from the top of a young tree it was gently slowly but surley has been pulled right down in a letter ” P ” by hand then pulled through the hole that went right through the trunk , sealed with grafting wax , braced with 5 mm dia Bonsai soft wire that had bee run through some soft plastic tube to stop it cutting in at the points of contact to secure it and left to grow .
This was done to make two new low down branches to balance th tree in later years . It can also be used to put two lateral leaders in low down .
Again where the leader passes through the drilled trunk you will need to remove outer & the inner bark in the prescribed manner so you have only exposed the Cambian layer showing . Don’t over do it and cut too much out so you only have wood left …they won’t grow .
One side of these cleaned of bark ( At the point of joining only ) leader must be a good contact fit to the cambium layer of the host tree so use a caliper to measure the diameter to discover what drill size you will need .
It’s worthwhile spending a few hours or so learning how to cut the outer bark off then shaving the inner bark to understand what the cambium layer looks like on each particular tree.
If you go too far and cut everything out till you only have the wood of the tree , there will not be any path of nutrients to pass through & the cutting / graft will fail
Most of these sort of graftings are done in early spring when the sap starts to rise in the host plants as the growing season then gives you a far greater chance of the host pant accepting the newcomer .
Re disease on your tree fence ..
If there is any disease that will totally kill a single tree off in a single attack then yes it could be a problem ..happily there are not many such diseases that cannot be treated using natural products that fully comply with the sites ethos .
As you’ll have many trees close together most of the time any other disease can be cut out and the bare wound sealed with a simple sealing compound .
Want to try your hand at grafting?
Want to practice other kinds of grafts? The University of Minnesota Extension Service has a good online guide, including illustrations, for many kinds of grafts.
Grafting is, at its simplest, wounding and healing. It’s the gardener’s way of taking advantage of a tree’s natural repair mechanisms. The growth of a trees trunk and branches occurs in a layer called the cambium, a greenish tissue that lies just under the tree’s protective bark. One unique talent of the cambium layer is that if it’s cut or torn, the two pieces will grow back together again. Grafters make use of this by cutting parts of the trees they want to graft together—taking a branch cut from one tree and putting it over the spot where a branch has been removed from another—and securing them in such a way that their cambium layers are in contact with each other. Over time, these layers will grow together, and the grafted part will become just another branch of the tree.
There are some good reasons to put a tree through all this injury (besides getting it to grow three different fruits). Consider orange trees: the roots of the tree that produces the sweet orange that we know and love can take up a virus that effects the growth of tree bark. The roots of the less-loved sour orange, however, won’t accept this virus. So by grafting sweet orange buds onto sour orange trees, growers in places like Texas protect their crop from disease. Grafting can make trees resistant to a variety of factors, including cold, drought, and microbes.
A second reason to graft is that some tree families, such as citrus, don’t reproduce reliably. Oranges, for example, are either seedless, or are hybrids that may produce a tree that is somewhat different from its parent. Grafting gives growers a simple way to reproduce fruit trees without having to rely on seeds.
© Bonfante Gardens
Ancient farmers and gardeners probably got the idea for grafting from nature itself. Young trees that sprout close together may graft as they grow up. Occasionally the branch of one tree will grow into the crook of another, and the pressure will injure the bark enough to allow the trees to graft. The creeping fig tree will graft its own branches in a tangle around another tree it uses for support. Other plants, such as rubber trees, are known to graft with each other at the roots. There are records of gardeners grafting in China and Mesopotamia as early as 2000 BC. Grafting was common in ancient Greece. In Renaissance England, grafters began making tree sculptures, and some artists and horticulturists continue the tradition today.
For pictures of some fanciful grafts, check out the Circus Trees at Bonfante Gardens in Gilroy, CA:
Turn Your Favorite Tree Into Many, by Grafting
WOOSTER, Ohio — There’s a gardening skill called grafting. It’s used a lot on apple trees. And it can help you turn a favorite tree — whether an apple, a pear, a dogwood or another — into more new trees just like it.
When someone grafts a tree, they splice a scion — typically a twig or other cutting — from one tree onto the rootstock — the roots and stump — of another. It turns them into a single new tree that features the best traits of both.
“There’s satisfaction in watching a plant you grafted turn into a large tree,” said Paul Snyder, program assistant at Wooster’s Secrest Arboretum, who’s giving an upcoming workshop on the topic.
The arboretum, part of the Ohio Agricultural Research and Development Center, is holding its annual Summer Grafting Workshop from 8 a.m. to noon July 20.
The rootstock of a grafted tree typically provides helpful basic features such as resistance to disease or hardiness in winter.
The scion, meanwhile, is usually cut from a favorite or outstanding tree — a tree that a gardener wants to duplicate. That tree might produce especially tasty apples, for instance. The new grafted version benefits from the stronger rootstock. It also will flower or bear fruit much sooner than a tree started from seed.
Skill works on ‘almost any deciduous tree’
Snyder said he grafts new trees every year, especially some of the arboretum’s rarer crabapples. He said it’s fun, challenging and fairly inexpensive.
“It’s a skill a home gardener can apply to almost any deciduous tree,” he said.
The workshop will emphasize chip budding, which Snyder called a “nearly universal graft” that’s easier to learn than other methods.
Chip budding, according to its Wikipedia entry, involves splicing a chip of wood containing a bud from a scion into a cut that’s made in a rootstock. The bud grows to become a tree.
Bring your own scions if you want
Snyder will provide scions and rootstocks for the workshop’s participants, who can take home the trees they create.
But he’s also encouraging participants to bring scions from trees in their own gardens, especially apples. There’s big interest in grafting fruit trees at home, he said. Plus, sometimes those trees have a history.
“A lady brought scions from a Johnny Appleseed apple tree last summer,” he said.
How to register
Registration for the workshop is $35 for members of the Friends of Secrest Arboretum and $45 for nonmembers. Details and a link to register online are at go.osu.edu/2017SummerGrafting. Call 330-263-3761 for more information.
The workshop will be in the arboretum’s Jack and Deb Miller Pavilion on Williams Road. OARDC’s main entrance is at 1680 Madison Ave.
OARDC’s rootstock, as it were, is the Scarlet and Gray: The center is part of The Ohio State University — specifically, its College of Food, Agricultural, and Environmental Sciences.