Fruit Tree Propagation - Bark Grafting
As consumers change their preferences for the apples they most enjoy, growers can convert portions of their orchard to these exciting new cultivars.
This project is supported in part by the Agriculture and Food Research Initiative of the National Institute of Food and Agriculture, Grant # 2015-70017-22852.
- [Instructor] Grafting is a technique every fruit grower should be familiar with as it allows you to test a new variety in your own orchard or to replace an obselete variety.
Today we'll review a bark grafting technique that will allow you to quickly to tap work a block over to a new variety.
First we'll discuss some reasons for using a bark graft, then we'll go through the steps of performing a graft successfully.
The session will conclude with tips on caring for the trees in the year after grafting.
So to start why bark graft?
The industry has an increased demand for premium apple cultivars, varieties like honey crisp, fuji and pink lady which is driven by the consumer.
It is helpful if we can quickly convert portions of our acreage from the older varieties to the new and more popular cultivars.
Rather than ripping out the entire block and starting all over top working allows us to replace these old varieties quickly while keeping the old root systems in place.
Bark grafting has a high success rate which makes the technique an excellent option.
Keep in mind if you plan to propagate from your own trees all royalty should be reported and paid if you will be propagating any licensed scion materials.
To bark graft you will need a grafting knife, grafting compound and either a nail gun with wire nails or electrical tape, either one will do.
Bark grafting is best performed in the spring as buds in the orchard are starting to open and the bark of the root stock slips.
It can be done successfully up to the 30 days past full bloom.
Your scion wood should be collected from the most recent season's growth from fully dormant trees between January and February.
Make sure not to collect wood while frozen.
The best shoots are about the thickness of a pencil.
Larger or smaller pieces can also be used.
Begin by collecting 12 x 18 inch sections from straight growing vertical shoots and wrap them in moist but not wet shpagnum moss.
In addition to keeping the scion wood from drying out the sphagnum moss has antifungal compounds that help prevent wood rot.
Next place the scion wood and sphagnum in non perforated plastic bags and store it in a refrigerator or cold storage at a temperature just about 32 degrees Fahrenheit to keep them dormant until you're ready to graft.
Avoid storing the bud wood with apples or other crops that may give off ethylene as the ethylene produced may cause the buds to abort.
To prepare the stock cut the tree at a convenient height from the ground, leaving nurse limbs so the tree can supply carbohydrates to the root system while the grafts are becoming established.
The tree stock can be cut ahead of time but make a two inch fresh cut at the time of grafting to prevent the graft from drying out.
To prepare the scion cut an inch from the bottom to create a fresh cut.
Next make a diagonal cut below and opposite to the lowest bud so the cut surface will face towards the inside of the tree and the bud towards the outside.
Use your knife to ensure the cut is smooth as this will maximize contact between the scion and the stock.
Then remove the cut scion from the rest of the scion wood by cutting a quarter inch above the top bud.
The final product should be a three to six inch bud wood that has at least three vegetative buds.
Locate the cambial zone of the stock.
That's the area between the bark and the wood of the tree where new cells differentiate.
Make two vertical cuts into the stock between the bark and the wood approximately the width of the scion.
Using the tip of your knife peel back some of the bark from the wood to expose the cambium.
Peel back enough so that the exposed wood of the scion will be against the stock cambium.
Insert the scion into the stock keeping the cut side of the scion flush against the stock cambium.
Be careful not to damage the bark of the stock as the bark helps to keep the graft from drying out.
Next staple a wire nail through the bark and the scion to secure the graft in place.
Insert multiple scions, one for every two inches of stock circumference.
Inserting more scions will allow the wound stock to heal over faster.
Use grafting compound to seal all of the exposed surfaces.
Also apply the compound to the tops of the scions to prevent them from drying out.
Reapply the grafting compound if needed.
Instead of using nails electrical tape can be wrapped around the graft to secure it in place.
Wrap tightly and then apply the grafting compound as you would normally.
Once you've grafted all of your trees you will need to continue caring for them to ensure successful establishment.
You do this by trimming any fruit off the nurse limbs because young fruit compete against the growth of the scions.
In the first season we want the scions to grow vigorously so that we can secure them to the trellice.
In these trees grafted last year we see how vigorously the scions grew.
If you inserted multiple scions you may want to select the best two and cross them as this will relieve stress on the unions.
Leaving two will allow the wound to heal faster.
Use temporary stakes to provide support to the new scions.
Once the new tree is established remove the nurse limb.
After the first year you can select one liter and remove the other or you can train the weaker scion down to a horizontal position and treat it as a scaffold limb.
After another year the combined growth of the two scions should bridge together and begin to heal most of the exposed surface of the stock.
Scions should be growing vigorously and a small crop of fruit may be developing.
With this information you should now be able to go out and convert of your rows over to exciting new varieties.
For more information consult the Penn State extension publication Grafting and Propagating Fruit Trees.
Special thanks to the horticulture team at the Penn State Fruit Research and Extension Center for their help in the making of this production.