Bark Grafting
To the left is a smaller diameter topworked tree that required only three scions. Each scoon has three buds. Two buds is usually considered the minimum per scion (but also the most common), although some grafters might use 3, 4, or even 5 per scion). Three steps remain for this bark graft
The bark graft to the right was on a larger diameter understock and required 5 scions. The diameter of the limb or stump determines the number of scions required. Some of the scions on this example have three buds and other have two. In step #2 athletic tape was wrapped tightly around the outside of all of the bark holding the scions in place against the cambium layer. Then in step #3 play dough was used around each scion to prevent the sealant from dripping down behind the scion. Finally, in step #4 Doc Farwell's Seal & Heal was used to seal all cut surfaces including the ends of the scions. |
Some Examples:
The photo to the immediate right is of a large pear tree that was successfully topworked without leaving a nurse limb. Although it is somewhat hard to make out in the photo, there are actually 6 successful bark grafts on this stump. The rule is the larger the stump or limb, the more scions that are needed because over time these must completely dover the cut surface of the stump or limb. The photo over on the far right shows pear trees that have been topworked for a longer period of time and now have about 8 foot of growth. They have been allowed to grow for a few seasons without pruning to rapidly cover the top of the stump. During the next pruning season limbs will be removed from the center to allow in more sunlight and give the topworked trees their final form. Limb spreaders could also have been used to let more light into the center as they were developing a new limb structure. |
When to topwork:
The extension bulletins on grafting all emphasize that the rootstock (in the the case of topworking, the established trees you are grafting on to) must be actively growing, while the scion to be grafted must be dormant. The reason that the tree must be actively growing is that in order for a union between the scion and the rootstock to take place there must be active cell division in the cambium layer (the region of dividing cells just under the bark) of the rootstock. Many of the bulletins also emphasize avoiding topworking when there has been a recent cold spell (which slows cambial activity). It is necessary to wait for about a week after the weather starts to warm up again so that the cambium cell division can become active again. It is important to only topwork when all danger of late heavy freezing is past.In Eastern Washington and North Idaho this means that grafting will take place sometime in mid-April.
Whitney Grafting Face Book content related to bark grafting:
Whitney Grafting, a Yakima firm that does grafting for commercial fruit and nut growers throughout the US, has maintained a Face Book page for its commercial customers since 2017. This FB page has some photographs and brief videos that can be very helpful to those of use with home orchards that need to graft from time to time, especially to topwork existing trees. You can get to that Whitney Grafting FB page here.
Below I have created an annotated listing of the FB dates where the picture or video illustrates the application of bark grafting to topworking established trees to change the variety.
1. May 29, 2022 Four grafts on stump about 6 to 8 inches across. If the stump were larger then more grafts would be needed. Eventually the grafts will grow to cover most of the surface of the stump. The stump would have been freshly cut the same day that that the grafts were applied. However, the larger limbs may have been cut and removed several days (but there would be a fresh cut the day of grafting).
2. May 4, 2022. This photo shows the results of not having living grafts all the way around the outside.
3. May 3, 2022 "Yes it will grow . . . " Shows 16 scions on an 18' diameter stump. See follow-up photo below of sprunted scions.
April 27, 2022 "Yes we do big trees . . . " Shows scions on main stump and also on large side limbs. Basically topworking the tree back into the same shape it was before, but with a different variety.
4. May 11, 2021 Really good closeup of knife movements used in bark grafting.
5. May 4, 2021 Video that shows all 4 steps (each done by a different person in large project like this for a commercial customer) Step 1 is cutting and placing the scions. The scions are tapered on both side to form a kind of wedge. The bark on the understock is cut clear to the woody material (heart wood) to provide a cleft for the scion to be slipped into. The pressure of the bark closing in on itself around the cut is what holds the scion in place. Step 2 is wrapping the outside of the bark with something like the fabric used in athletic tape (but without the adhesive - I actually use athletic tape with adhesive backing in my amature bark grafting). Step 3 is placing play dough around the top of the scions to prevent the sealant in Step4 from dripping down behind the graft and preventing the formation of a callusing union between the cambium of the understock and the cambium of the scion. Step 4 is covering all of the cut surfaces (including the tops of the scions) to prevent them from drying out. In this case the worker is applying Doc Farwell's Seal and Heal with a paint brush. It is preferred over the asphalt-based sealers.
6. April 11, 2019 Another good example (good detail) of the 4 steps used in bark grafting. Note that no "nurse" or "feeder" limb is left on the tree. All of the nutrients from root storage go directly and only to the scions. This why there can be so much new growth in a single season when an a mature tree is topworked.
7. May 29, 2018 Example of use of "feeder"/"nurse" limbs to deal with bleeding problem common in topworking.
8. May 31, 2018 Example of making a "relief cut" to deal with a bleeding problem common in topworking in Michigan.
9. May 4, 2018 Big stump with 12 scions. Each scion has two buds.
10. April 19, 2018 "Lots of this new apple (Cosmic Crisp) coming to market soon." Note that the undestock is about 3 to 4 inches in diameter (fairly young trees being converted over to new variety) in comparison to understock that is 12 inches across.
11. May 17, 2017 Video of side limbs as feeder limbs that will later be cut off after the topworked grafts in the center get established.
12. May 11, 2017 Video showing what the trees look like before getting a chainsaw and cutting back major limbs to topwork but leaving a few feeder limbs.
13. May 9, 2017 is a post about the differences in cultural practice in terms of low trees vs. high trees. The caption says, "This is how (high) we used to graft orchards before everyone wanted them cut off down low."
There are also some entries showing the positive results of using green wood scions (instead of the usual dormant wood which weren't available).
1. July 10, 2023 "We have been doing experimental grafting with green wood instead of dormant wood." Pretty amazing (unexpected) results.
2. July 18, 2019 "This tree was bleeding . . . " Replaced failing dormant wood grafts with green wood scions because dormant wood wasn't available.
3. April 20, 2019 Grafts made with green wood not only survive, but show strong growth.
4. August 25, 2018 Shows success of green wood bark grafting done about a month before on July 24th.
5. August 24, 2017 Shows use of green wood to make bark grafts in summer.
The extension bulletins on grafting all emphasize that the rootstock (in the the case of topworking, the established trees you are grafting on to) must be actively growing, while the scion to be grafted must be dormant. The reason that the tree must be actively growing is that in order for a union between the scion and the rootstock to take place there must be active cell division in the cambium layer (the region of dividing cells just under the bark) of the rootstock. Many of the bulletins also emphasize avoiding topworking when there has been a recent cold spell (which slows cambial activity). It is necessary to wait for about a week after the weather starts to warm up again so that the cambium cell division can become active again. It is important to only topwork when all danger of late heavy freezing is past.In Eastern Washington and North Idaho this means that grafting will take place sometime in mid-April.
Whitney Grafting Face Book content related to bark grafting:
Whitney Grafting, a Yakima firm that does grafting for commercial fruit and nut growers throughout the US, has maintained a Face Book page for its commercial customers since 2017. This FB page has some photographs and brief videos that can be very helpful to those of use with home orchards that need to graft from time to time, especially to topwork existing trees. You can get to that Whitney Grafting FB page here.
Below I have created an annotated listing of the FB dates where the picture or video illustrates the application of bark grafting to topworking established trees to change the variety.
1. May 29, 2022 Four grafts on stump about 6 to 8 inches across. If the stump were larger then more grafts would be needed. Eventually the grafts will grow to cover most of the surface of the stump. The stump would have been freshly cut the same day that that the grafts were applied. However, the larger limbs may have been cut and removed several days (but there would be a fresh cut the day of grafting).
2. May 4, 2022. This photo shows the results of not having living grafts all the way around the outside.
3. May 3, 2022 "Yes it will grow . . . " Shows 16 scions on an 18' diameter stump. See follow-up photo below of sprunted scions.
April 27, 2022 "Yes we do big trees . . . " Shows scions on main stump and also on large side limbs. Basically topworking the tree back into the same shape it was before, but with a different variety.
4. May 11, 2021 Really good closeup of knife movements used in bark grafting.
5. May 4, 2021 Video that shows all 4 steps (each done by a different person in large project like this for a commercial customer) Step 1 is cutting and placing the scions. The scions are tapered on both side to form a kind of wedge. The bark on the understock is cut clear to the woody material (heart wood) to provide a cleft for the scion to be slipped into. The pressure of the bark closing in on itself around the cut is what holds the scion in place. Step 2 is wrapping the outside of the bark with something like the fabric used in athletic tape (but without the adhesive - I actually use athletic tape with adhesive backing in my amature bark grafting). Step 3 is placing play dough around the top of the scions to prevent the sealant in Step4 from dripping down behind the graft and preventing the formation of a callusing union between the cambium of the understock and the cambium of the scion. Step 4 is covering all of the cut surfaces (including the tops of the scions) to prevent them from drying out. In this case the worker is applying Doc Farwell's Seal and Heal with a paint brush. It is preferred over the asphalt-based sealers.
6. April 11, 2019 Another good example (good detail) of the 4 steps used in bark grafting. Note that no "nurse" or "feeder" limb is left on the tree. All of the nutrients from root storage go directly and only to the scions. This why there can be so much new growth in a single season when an a mature tree is topworked.
7. May 29, 2018 Example of use of "feeder"/"nurse" limbs to deal with bleeding problem common in topworking.
8. May 31, 2018 Example of making a "relief cut" to deal with a bleeding problem common in topworking in Michigan.
9. May 4, 2018 Big stump with 12 scions. Each scion has two buds.
10. April 19, 2018 "Lots of this new apple (Cosmic Crisp) coming to market soon." Note that the undestock is about 3 to 4 inches in diameter (fairly young trees being converted over to new variety) in comparison to understock that is 12 inches across.
11. May 17, 2017 Video of side limbs as feeder limbs that will later be cut off after the topworked grafts in the center get established.
12. May 11, 2017 Video showing what the trees look like before getting a chainsaw and cutting back major limbs to topwork but leaving a few feeder limbs.
13. May 9, 2017 is a post about the differences in cultural practice in terms of low trees vs. high trees. The caption says, "This is how (high) we used to graft orchards before everyone wanted them cut off down low."
There are also some entries showing the positive results of using green wood scions (instead of the usual dormant wood which weren't available).
1. July 10, 2023 "We have been doing experimental grafting with green wood instead of dormant wood." Pretty amazing (unexpected) results.
2. July 18, 2019 "This tree was bleeding . . . " Replaced failing dormant wood grafts with green wood scions because dormant wood wasn't available.
3. April 20, 2019 Grafts made with green wood not only survive, but show strong growth.
4. August 25, 2018 Shows success of green wood bark grafting done about a month before on July 24th.
5. August 24, 2017 Shows use of green wood to make bark grafts in summer.