Having read many articles on how to graft grapevines, and having tried a number of processes that failed, I decided to test anew process using my seedless Concords. If this works I will post the results later this fall.
This weekend I discovered that one of my five Concord grapevines was seedless as I tested the grapes that were ripening. The seedless ones were a real treat, so I decided to risk a number of this year’s green buds to bud several of my other vines to convert them to seedless. Having read thru the portions of Plant Propagation Principles and Practice, by Hartmann & Kesters, that relate to summer budding, and realizing I am practically at the end of the summer grafting season, I used a test technique that I hope works.
To maximize cambium contact I used a modified chip bud by using a diagonal slice on the rootstock as well as the back side of the chip bud. Given that my bud wood diameter is quite a bit smaller that the root stock, the diagonal slice into the rootstock affords a neat way to match cambiums. Pic #1
Although my pic is blurred you can see how the bottom back side of the budchip is trimmed to fit under the overlapping bark. Pic #2
Once inserted, the chip is sealed with plastic tape, leaving the the bud and petiole exposed. In this case I am using a bud that also has a sucker sprouting. It will be interesting to see if either or both survives. Pic #3
Next to achieve a good level of compression I used a green rubber band to tighten down the graft. In about two weeks I will remove the rubber, while keeping the tape secure around the graft. Pic #4
Then I covered the graft with a clear plastic tent to create a greenhouse effect since our daily temps will be in the mid 60s to 70s over the critical next three weeks as the grafts callous. Pic #5
Today I completed 7 of these experimental grafts. Since the bark was not slipping, I chose to use the modified chip bud rather than trying to use a T bud. To increase compression I am applying a rubber band for at least 14 days. And to achieve a callousing temperature over the next three weeks I am covering the grafts to hold moisture and heat as high as possible. Since the vines are not pumping sap this late in the season, I may not need to cut the vines below the graft, but I will continue to monitor over the next few days. I will follow up later to show results, success or failure!
Today I checked my 6ea seedless grape grafts to find them all looking heathy, petioles fell off, buds not molding. I left the clear plastic covers off for an hour while sun was out to dry each out, re-sawed the bleed cuts below each (vines had built up a sap from bleeding recently, but the graft areas were free of sap). Each graft still sealed around the graft union with plastic tape. Plan to check each month for sap buildup, and mold, although vines are now dormant.
Spring of 2021 bud monitoring, update:
On 4/23/21: I noticed that my concord vines in general were well past bud break with leaves about 1”-2” in growth. Yet my 7 experimental chip buds were just beginning to open. So I began to consider forcing these new buds? I decided to wait and monitor given all 7 buds appeared to be breaking open their bud sheaths.
4/26/21: As I pondered notching over the weekend, I observed that my native seedless concord had been breaking bud, but at a much slower pace than the other grape vines. So it occurred to me that I could not expect this cultivar’s chip buds to open any sooner or faster than the mother plant! This factor as well as the placement position on the lower portion of my rootstocks giving them no apical dominance relegates them to a lower status of energy potential for bud growth. My picture on this date illustrates how the seedless plant buds are growing much slower than the other concord varieties. So I decided to postpone notching until daytime highs are above 70F.
4/30: All 7 buds tips are now light green. I removed all graft union seals to inspect. All but one had calloused completely. One was calloused on both ends but the center portion appeared to have a space open. I resealed all with a softer tape to prevent desiccation while avoiding girdling. The only question now is whether I will need to notch these chip buds? I am waiting to see if higher daily temperatures above 70F will bring them out before deciding to notch.
This technique far exceeds any process I have tried in past years. If I had only seen the below paragraph in the grafters handbook several years prior, I would have saved a lot of wasted efforts! If you have grapes to graft, I highly recommend this method of fall or early spring prior to bud break grafting.
