Grafting and Budding Fruit Trees

Asked March 17, 2016, 8:09 PM EDT

Regarding this article, You give no advice about aftercare of grafted rootstock-scion material, with regard to whether the rootstock on which one is grafting is bare root (which is my parameter, grafting various apples on Bud-9 rootstock), or in-ground rootstock (and I have some of this too, that I plan to deal with shortly).

My friend and I just did a bunch of cleft and whip grafts of a variety of apples onto Bud-9 stock. We're hoping Bud-9 is hardy enough to handle at least protected Otter Tail County environments - wish us luck! But now that we've done what we think is a pretty good job of grafting, we're not certain of how to proceed next. My inclination is to pot these grafts up and store them cold - 35-45° - then bring them out into post-frost outdoor growing conditions in early May. My friend's (and he's the nurseryman, with more experience than I) is to store them wrapped in plastic, roots nested with damp peat, in cool conditions for 3 or 4 weeks, with the idea that this allows a callus to form on the cut spots; then pot and move into growing conditions. Being we covered all the cut spots with grafting compound, I'm not sure what the beneficial effect of this storage interval might be (won't the grafting compound obviate the need for callus development?), while I *would* be concerned about lack of air movement inside the plastic bag. Nor do I think the callus would be any less likely to develop in the open, cold, but vaguely moving air, than inside the confines of a plastic bag. The main difference that I can see would be humidity: plastic bag/cold storage means more humidity around the graft. (Potential for fungi/mildew development, yet prevention of drying out of the cut surfaces of both rootstock and scion?) Potted but in open air/cold storage means more air movement around the graft (perhaps too much in this critical zone?), meanwhile supplying well-controlled humidity around the rootstock's roots. Is this general outline correct? Which of these conditions tends to be more beneficial for the future apple tree? And does it *really matter,* until both rootstock starts to send growing signals, and scion pull that energy, hopefullsy at the same time?

Furthermore, there is the question of how to handle the rather long, trailing roots on the Bud-9 rootstock. These youngster trees will be small for a while, and surely should fit easily into gallon-size pots. But if we do that, should the roots be cut back, trimmed, so that they don't do that circular (deadly under stressful conditions) thing that so many pot-grown trees do? And is it the critical thing for ultimate success that all young trees be constantly moved up to higher-sized pots as required, until they can be planted out, so that their roots never start growing into circles?

At any rate, I would request that the above-cited article be refined and extra detail added, with regard to the condition of the rootstock (bare root, vs in-ground), and follow-up handling. I would also appreciate advice about truly ideal conditions - even if expensive, if one were to do this for commercial production - such as potentially always up-potting when new root growth reaches the edges of an existing pot. Production of premium-health trees is my ultimate goal. I may only do this as a private hobby orchard; but it would still be great to know what would actually be BEST.

With all thanks,

Joan Covington

Otter Tail County Minnesota

5 Responses

You questions are beyond my expertise but I can suggest how to proceed and comment on several of your proposed actions. Putting plant material at -35 F will kill it. Trees need to be dormant to survive freezing temperatures and entering dormancy is a process that takes time. Cool storage is enough to suppress growth. The graft does need to form callius tissue, that is how the plant makes a union between the two pieces. Grafting compound promotes growth. Keeping it moist keeps the tissue from drying out and being killed by dehydration. I highly recommend watching YouTube videos about grafting fruit trees. If you stick with it and watch at least 5 you will learn what the common practices are and what has been successful. Then divide your collection into several groups and give each group a different treatment that others have had success with. See what works for you and continue your experiments next year. Grafting is an art that often takes a bit of practice. Also the library has books on grafting fruit trees and there are probably methods and procedures to learn about that will work for you and your climate. I will see if I can find some resources for you and add them to this response if they look like they will be helpful. Good luck with your fascinating project.

Oh no, I didn't mean 35 below! That was a dash, indicating temporary initial storage temperature of between 35 and 45 *above*, until it's time to start encouraging growth. We're not so concerned with the grafts themselves - we actually think we did a pretty good job with that part. The question is more about what to do *next* with these young trees. Maybe I'll try a few YouTubes, although generally I find them to be pretty elementary or not applicable to Minnesota conditions.

I don't know who writes the articles that go on the UM Extension website, but again, I do think the article I mentioned above leaves a sort of hole, with regard to what to do once you've finished the grafts. Maybe someone from the University's apple research department could address that.

Thanks for your time!


Here are a couple of references that maybe useful.

I am glad you weren't planning on storing them at -35, I was puzzled, but one never knows, and you might have access to a essentially a dry ice freezer.

I have found Youtube videos from nurseries, PBS, webinars etc to be useful,
although I agree, there is lots of junk to sort through.

Extension staff update the information online and unfortunately there is lots to do and not many people to do it. They also are limited by what has been verified in a research trial. They can't publish
anecdotal information.
Your local extension office can be contacted and so can the fruit breeders. They get many inquiries so it may take some time for an answer.

Hi Jennifer, I found someone who has had some success. Here are his suggestions.

I did some of this for my Plant Propagation lab work at the U a little while back. She should follow the nurseryman’s advice if these are to be either field planted or better heeled-in for the first year in a sand or pebble rooting bed. If however they are destined to be container grown from spring planting on, then she can also just pot them up now and cool store in the manner she indicated. The wax or other grating compounds are intended to promote better callusing results, by preventing drying at the wound site. She should use air pruning slotted containers or fabric root pruning pots for the stock and trim all roots back to the container dimensions so they don’t begin to circle and girdle whatsoever.
Here’s a good article on bench grafting.