I’ve been using a teaspoon of vitamin C for the past few years when rehydrating scions, along with Superthrive, and I’m curious to hear others’ thoughts. Here’s my reasoning:
Vitamin C (ascorbic acid) has been shown, in certain plants, to increase grafting success by acting as an antioxidant that prevents cell damage from phenols and oxidative stress. This, in turn, promotes callus formation and enhances vascular connections. All of the studies I’ve seen have been conducted on herbaceous plants, and vitamin C is used commercially in some instances for this purpose. To my knowledge, there are no studies specifically examining vitamin C use in grafting fruit or nut trees.
I can’t say definitively that it helps, but I have used it for several years when rehydrating scions for grafting numerous Rosaceae, mulberry, and others, and I can say that it certainly doesn’t seem to hurt. Depending on which AI you ask, it will either say it helps significantly or has no effect at all. Since grafting difficulty generally increases with higher phenolic content—and vitamin C helps reduce phenol-related cell damage—I could see this being particularly useful for more difficult-to-graft trees. Nothing I graft is considered especially difficult, so it probably provides little to no benefit for me, but I have a large bag of it, so I figured I might as well use it.
Horticultural micropropagation work demonstrates that very low-dose ascorbic acid (~0.5 mM, ~88 mg/L) improved survival and rooting in sweet cherry microshoots, suggesting physiological benefit without toxicity:
In Prunus avium microshoots, 0.5 mM (~88 mg/L) ascorbic acid improved establishment/survival.
I first fully dissolve one teaspoon of ascorbic acid in a small amount of water. I then add this solution to a glass baking pan, where the scions are fully submerged in approximately eight cups of water with one drop of Superthrive. The length of time the scions remain submerged depends on their condition. I follow the procedure outlined by @Barkslip with the addition of ascorbic acid.
I’m not certain that it helps, but it certainly doesn’t appear to hurt.
Nice find—that’s an interesting article. The doses mentioned are extremely low. I imagine the beneficial dose for grafting scions would be significantly higher than what’s used for rooting microshoots, as described in the article, though I can’t say for certain. I do know some pepper grafters who make a paste of vitamin C and dip both ends into it before grafting. The dose at which vitamin C is beneficial is probably very different from the dose at which it becomes detrimental. You’ve made me realize that I should have included a disclaimer in my original post.
I hope no one takes anything in these posts as advice in any way. Just because something hasn’t been detrimental for me doesn’t mean it won’t be detrimental for you. My only goal is to encourage discussion and possibly experimentation.
A patent application doesn’t mean much on its own, so take this with a grain of salt, but it does mention vitamin C as an ingredient in a “grafting cream” said to be beneficial for grafting persimmon and Chinese chestnut.
“The tissue juice that vitamin C can alleviate the kind such as persimmon, Chinese chestnut grafting mouth forms polyphenols because of oxidation and affects the healing forming interlayer; 6-BA plays the effect accelerating cambial cell division and the healing of grafting mouth; Carbendazim can suppress the germ of grafting part to grow.”
“The main component of this grafting cream is starch, rosin, water, alcohol, vitamin C, 6-BA, carbendazim.”
Vitamine C is an antioxidant, but so are polyphenols. So, the notion that it antagonizes the action of phenols does not make sense to me.
Wounding is necessary for callus formation and oxidative mechanisms via the formation of reactive oxygen species play a role in this. So, one would think that Vitamin C would counteract this. But Vitamine C solutions are also acidic, so, they have some anti microbial effect, which may be what is driving the effect (if there is one). Some people dip scions in dilute bleach or hydrogen peroxide to get a sterilizing effect. Probably not necessary IMO, unless your scions got mold.
You’re right—both ascorbic acid (vitamin C) and polyphenols are antioxidants, and antioxidants can have powerful effects.
When you cut into an apple, the exposed tissue often turns brown fairly quickly. This browning is largely due to the oxidation of phenolic compounds in damaged cells, a reaction catalyzed by enzymes such as polyphenol oxidase. One common way to slow this process is to soak sliced apples in a solution containing vitamin C or lemon juice. Ascorbic acid slows the oxidation of phenolic compounds and keeps the fruit lighter in color for a longer period. I use this approach with several fruits before dehydrating them, and the difference in color retention is significant. Fruits with higher natural vitamin C content also tend to brown more slowly than the same fruit with lower vitamin C levels.
The browning that occurs when an apple is cut is not entirely different from what happens when a scion is cut from its parent tree. In both cases, wounding triggers the oxidation of phenolic compounds, leading to tissue browning. In grafting, excessive oxidation at the cut surfaces can contribute to the formation of a necrotic (dead) layer at the graft union, which may interfere with the establishment of vascular connections between the scion and rootstock.
My line of thinking is that, just as vitamin C can slow browning and help preserve fresh tissue in cut fruits, it might also help keep scion tissue viable for a longer period and potentially reduce oxidative damage at the graft union. This, in turn, could improve the chances of successful graft union formation.
There are studies showing that vitamin C can be beneficial in grafting or tissue culture systems in certain plant species, and there is a substantial body of research examining the role of phenolic compounds and oxidative processes in graft success. That said, it is entirely possible that vitamin C has no practical benefit—or could even be detrimental—when grafting fruit or nut trees. I welcome discussion and differing opinions.
I think that it is possible that ascorbic acid does have an effect through preventing the oxidation of polyphenols at the cut. But more likely in my mind that the browning (oxidative damage) is triggering repair. If one really wanted to find out, then you would have to run a large trial, preferably blinded (two solutions, one control, the other one ascorbic acid, where the grafter does not know which one is which). Doubt that anybody has done this.
I agree that the oxidative damage that occurs when cuts are made for grafting triggers an essential repair response. Initial oxidative stress plays an important signaling role in wound healing. However, excessive or uncontrolled oxidative damage can interfere with this process and contribute to graft failure.
Enzymatic browning is a well-studied example of this problem. It is generally undesirable because it can lead to tissue necrosis at the graft union, preventing successful graft formation. Accumulation of phenolic compounds at the graft site is one factor commonly measured when assessing graft incompatibility. Certain nut trees are particularly difficult to graft in part because they contain high levels of tannins (a type of phenolic compound). When these tissues are cut, tannins can undergo enzymatic oxidation, forming a necrotic layer that inhibits vascular connection and graft union formation.
You also raise a good point that additional mechanisms may be involved, such as the potential antimicrobial effects you mentioned.
As far as I can tell, the use of vitamin C during grafting has not been studied in fruit or nut trees. However, there are published studies demonstrating its effectiveness in grafting or tissue culture work with peppers, tomatoes, cucumbers, clove, and other species.
You’ve made several interesting points, and I appreciate the discussion.
That seems like quite a bit of work for someone doing a lot of grafts, given the soak would have to be done after cutting the scion specifically for the graft. Presumably, if it is useful, it might be equally useful to also soak the mother at the point of the cut.
Then I asked CHAT.
CHAT GPT suggests that a soak is ineffective and unnecessary for a few reasons, mostly that the C doesn’t distribute well through the wood this way and that the ticket would be just to coat the cut parts of the scion and the mother tree immediately before grafting.
since this is dealing with oxidation topical application on the cut end I suspect would be all thats needed, you can pack a spray bottle with you to apply that and with so many grafts to make. you can make a control group.
I doubt vitamin C does much at grafting besides neutralizing alkaline water. I would think the plant has all the vitamin C it needs (just an opinion not baised on any actual testing). I keep my scions under water while grafting, mostly to keep air away and so they slide together (so the cambian doesn’t tear off the tounge), but also to keep them from drying out.
I am now wondering if there is a hormone that facilitates callus formation. Like maybe auxin or cytokinin.
Its about preventing oxidation damage on the cut end. Apples have vitamin C but a little more on the cut fruit stops browning.
That Vitamin C helps prevent this damage is not in question. the unknown is application at grafting time. i think its worth a shot why not add a little vitamin c to your soaking water.
Both cytokinin and auxin have been shown to promote graft union formation, and Superthrive contains both, which is why I use it in combination with vitamin C. Many micrografting protocols rely on agar, nutrients, ascorbic acid, and plant growth regulators. You’re right that grafting underwater helps minimize oxygen exposure and reduces oxidative damage at the cut surfaces. Hans Winkler and Lucien Daniel used underwater grafting to facilitate some of their more extreme grafts.
As noted above, directly applying vitamin C to both the scion and rootstock would likely be more effective at preventing enzymatic browning than soaking. I may experiment this year with a modified “grafting glue” similar to those used in micrografting, although agar would likely need to be replaced with a more practical substitute.
Just an FYI on AI answers—this post is now the one ChatGPT cites most often when I ask about vitamin C and grafting, so take it with a grain of salt.
I would be interested in the results if you try a study. I only do the classic “stick to branch” grafting, and nothing so fancy it involves lab work. My apple bench graft takes are over 90% and I’ve occasionally graft 100+ trees, sample size to prove a difference would be huge… Now on stone fruit I’m probably 25% on long term survival (for bench grafting). Didn’t realize Superthrive had Auxin and Cytokinin, but makes sense, I’ve used in in rooting cuttings in water with better results than water alone…but not better than water with a fish pump and air stone. (never tried superthrive and bubbles together).
There are many peer-reviewed articles showing the effectiveness of vitamin C in micrografting, and in some contexts its use is standard practice both commercially and in laboratory settings. You’re right, though, that there are very few peer-reviewed studies on using vitamin C for field grafting of fruit and nut trees, which is why I started this thread. I appreciate the constructive discussion, and I agree that AI can be an incredible tool in certain contexts.
As I mentioned above, I don’t think vitamin C would provide me much, if any, benefit personally, since I don’t graft particularly difficult material and don’t graft at a scale large enough to generate meaningful data. That said, I do think there are situations where vitamin C could meaningfully increase graft success rates.