Fruit Tree Propagation - Bench Grafting
Have an old heirloom tree that you would like to plant on modern, dwarfing rootstocks? Find a chance mutation that you would like to evaluate? Bench graft these varieties onto the rootstock of your choice.
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.
- [Voiceover] Grafting is a technique every fruit grower should, at least, be familiar with.
Today we'll take a closer look at performing a bench graft, so you're able to propagate your favorite varieties onto the rootstocks of your choice.
We'll start by discussing some reasons why we would want to bench graft.
Then, we'll go through the steps of performing a successful graft.
We'll conclude by talking about what to do with the bench graft once the union is formed and you have a new, two-part tree.
Let's begin with the reasons for bench grafting.
First, bench grafting allows for optimal cambial contact between the scion and rootstock, making for a strong union that heals quickly.
It allows us to preserve scion wood from older varieties that are hard to find, or new chance mutations we'd like to test.
By grafting to a dwarfing rootstock that comes into production much earlier than a standard or semi-dwarf rootstock, we can evaluate or enjoy eating the new fruit more quickly.
Keep in mind if you're working with an older variety, it could have latent viruses, so it's best to order certified virus-free wood from a reputable nursery, and, if you plan to propagate from your own trees, all royalties should be reported and paid if you will be propagating any licensed scion materials.
In addition to scions and rootstocks, you will need: a sharp grafting knife, grafting compound or grafting wax, and some grafting tape.
The best time to bench graft is from late March to early April.
You want both the stock and scion to be dormant.
Your scion wood should be collected from the most recent season's growth, from fully dormant trees between January and February.
Make sure you do not collect wood when it's frozen.
The best shoots are about the thickness of a pencil, though bench grafting can be performed successfully with scions up to one inch in diameter.
It is important that the scion and stock have similar diameters so the cambiums overlap each other.
Start by collecting 12-18" sections from straight growing, vertical shoots and wrap them in moist, but not wet, sphagnum moss.
In addition to keeping the scion wood from drying out, the sphagnum moss has anti-fungal compounds to prevent the wood from rotting.
Place the scion wood in sphagnum moss in a non-perforated plastic bag and store in a refrigerator or cold storage at a temperature just above 32 degrees Fahrenheit to keep them dormant until you're ready to graft.
Avoid storing the scions with apples or other crops that may give off ethylene, since ethylene can cause the buds to abort.
Stocks can be purchased from nurseries and usually come in bundles of 50-100.
Order ahead of time so that you will have them by the time you're ready to graft.
Keep them in moist sawdust and plastic, storing them in a refrigerator or cold storage close to 32 degrees Fahrenheit until you're ready to graft.
To prepare the scion, make a one to two inch diagonal cut from the lowest bud that will be on the graft.
Each scion should have two to three buds.
Then, make a downward cut starting a third of the way down the scion from the first diagonal cut.
It should be about half as long as the first.
Make similar cuts to the top of the stock, starting with the diagonal cut up through the stock.
Then, make the tongue cut similar to the one you made in the scion.
Here we can see the two cuts on the scion and stock.
The first cut is sloping, and the second cut starts about a third of the way down, and is half the length of the first cut on both.
The same cuts were made on the stock.
This graft is also called the whip and tongue graft.
The second cut creates the tongue which holds the scion and stock together.
When we bench graft, it's important that we try to match the thickness of the scion with that of the stock, as this will help ensure that the cambium layers of the stock and scion line up when they're joined.
If sizes differ, be sure the cambiums line up, as this will ensure good callous growth and healing of the wound.
Once you have made your cuts, insert the scion into the stock.
The tongues of the stock and scion should interlock, bringing the two into close contact.
Cut off the top of the scion, leaving two or three buds.
Once combined, the graft should be wrapped with tape to hold the graft firmly in place while the callous is forming.
The tape also helps keep the union from drying out.
From here, you may choose to wrap your unions using rubberbands.
These will provide a little extra pressure to keep the union in place.
It's important that the two pieces stay in place so that the callous tissue can join the scion and rootstock together.
Once wrapped with tape, dip the unions into warm grafting wax.
Make sure the wax isn't too hot to avoid damaging the cambium cells.
The wax will help seal the union and prevent the graft from drying out.
Rather than using wax, another option is to seal the graft using a latex-based grafting compound.
The wax will also help keep the union from drying out.
Once you've grafted your trees, store them in a cool, moist area for seven to 10 days in moist, aged sawdust.
After a week, the stock and scion should begin to produce callous tissue.
In the photo on the left, we see how the union looks about a month after grafting.
In the middle photo, this scion bud has already broken.
Bench grafts can be planted in the garden or a small nursery at a close spacing for a year or two before being planted in the orchard.
Extra care should be taken to ensure the trees remain well watered to prevent desiccation of the union.
After a year or two, the union should be completely healed and your tree should be ready for planting in the orchard.
With this technique, you can now go out and graft different heirloom or other unique varieties in your orchard onto the rootstock of your choice.
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.