I am in Zone 7b near Atlanta, and temperatures have been getting into the 80s. I have been grafting on some apples on year-old M7 rootstocks and pears on seedling Callery this season, mostly in the past month or so. Many of my grafts have pushed out some leaves but then the leaves have wilted and/or died, while the rootstock itself looks healthy and pushes healthy leaves. They are in full sun (probably 10+ hours), and I was thinking that the grafts might not be healed enough to transfer the water needed to counteract transpiration or something, but I wanted to hear if others had experience with this and combating it. If this is likely the problem, then should I try moving them to a shadier area until the growth is more vigorous?
I reckon you’re spot on. Direct sunlight for extended periods can dry the scion quicker than it can heal.
I use parafilm as my grafting tape, so I usually just wrap the entire scion to prevent the drying.
Before I switched to parafilm I used to coat the entire scion in a thinned down 40:40:20 mix of latex paint:wood glue:water.
I found that worked great as well (glue to help it stick, paint to seal it up, water so it’s not too strong and the scion can leave out through it).
The only scion I’ve lost to sun drying was one I tested covering with some aluminium foil, and it failed the same way your describe above, leafed out on it’s own energy reserves, but dried and died before the rootstock could heal to it.
Thanks for the advice Shane. I have covered all of my grafts completely in buddy tape, which is basically the same as Parafilm, but it’s the leaves that seem to be the main cause of the water loss. As much of a pain as it might be, I should probably temporarily pot them in the shade.
I’ve hear of people using a white paper sandwich bag over the top of fully wrapped, but leafed out scions to good success, cuts down on the direct heat, and reflects a lot as well.
Could be worth trying if it’s hard to shard the trees themselves?
I have a friend who does that for top working, and I’m glad you mentioned it; that would definitely be much less work than replanting twice.
What @schme16 said, both comments.
I grafted mine then laced a small tin can over top to keep sun out.
@schme16 and @marknmt , do you have any advice for paper bags when it comes to rain? It seems like the ones I’ve put on grafts would get in the way of anything that was trying to grow once they’ve been rained on once.
You should be rubbing out most of the leaf buds on the rootstock I think.
I’ve used Wilt-Pruf ( https://wiltpruf.com/) in such situations with success. Simply removing some leaves also works. If the graft is taking new leaves will follow quickly and hopefully have better support.
A graft can push some growth just from energy stored in the scion even if the graft did not take. Sudden wilt is a symptom of this situation. Do you have a pretty good “take” rate in grafts you have done previously?
That’s right. I have a bunch of mulberry sticks I just pushed in potting soil to see who roots. They are all pushing really nice leaves, but that won’t last as we know there are no roots yet.
I’m still waiting to see how many of my grafts fall in this category.
@Robert , I’ve had success with mulberry cuttings rooting but be careful. On Illinois Everberring and probably others, roots are very fine and easily pull off when disturbed. If they root leave them undisturbed as long as possible. If I did it again I would not transplant them until the fall or wait till the following spring.
I got four new apple trees from Cummins at the beginning of April. They recommended I prune back the tops to help them get established, so I cut off about eight inches from each and pushed those apical pieces halfway into the ground. All four are now leafing out. I stabbed a screwdriver into the ground 4x around each and drenched them with Superthrive. Probably nothing will happen, but it’s an intriguing experiment!
I am actually experimenting with rooting apple cuttings this year. I started some in February after wounding them by making a slit up them with a knife and then soaking them in an IBA solution overnight. I planted them out directly in my nursery bed, about halfway down, and just checked on them on Saturday. They were all about 6-8" long and varied from ~1/8" to ~3/4" thick. How well they are doing is directly correlated with thickness. The 1/8" ones have all died, while the 3/4" one has pre-root callousing all around the bottom and along the wound slits. Some of the ones on the thinner side have leaves but no callousing, but most of them have at least something. Some thinner ones have bottoms that are dead and rotten but have some callousing along the slit, which makes me think they would have failed completely if I had not wounded them. I can’t speak to how much the IBA affected them, but I may do a control next year. I recently moved them to pots in a shadier area, because there’s no way they will be able to contend with full sun in the Georgia summer until they develop actual roots.
You just never know. Small cost, big reward situations always tempt me.
Apples are easily rooted, even when I left a few pruning just laying on top of the ground last year, several weeks later one had rooted into the soil. So you can definitely get new trees, and most likely a clone in variety, but until it matures you may not know how the rootstock will perform.
When you are grafting at ambient temps well above the optimum, you have to do something to control the heat as well as solar exposure on new grafts. Leaving them fully exposed at 80F is not recommended. In your case you have little rootstock energy in the one ear old rootstock, and only a very little energy stored in each scion. It’s too late now in your area, but I have best results if I can graft one or two weeks before the ambient daily high temperature reaches optimum. For example I am still waiting on 70F in my area to graft persimmons, peaches, and pawpaws. But all other stonefruit grafts were performed several weeks before optimum.
Once your dormant scions are exposed to heat and light, they wake up. Ideally, you need at least 2 weeks of callousing time to heal the graft union before nutrients can flow between the rootstock and the scion. This assumes that you are near optimum temperatures. In an outdoor environment, it may take more time, since your temperatures are fluctuating and not at a steady optimum value around the clock. If your scion buds wake up prior to that, they simply wilt away as they consume the limited energy supply of sugars and carbohydrates stored within, while they are unable to receive nutrients from the rootstock.
So the comments of others on how to reduce stress during a heat spell are very noteworthy.
Here is the data that has worked well for me since I began to have success, good luck.
Callusing temperatures of Fruit and Nut trees
Many people ask: What are optimum callusing temperatures to ensure a good percentage of viable grafts?
Nectarines/Peaches – 18-26 deg C. ( 64.4 to 78.8F)
Apricots/Cherries – 20 deg C. ( 68F)
Plums – 16 deg C. ( 60.8 F)
Apples/Pears – 13-18 deg C. ( 55.4 to 64.4F)
Walnuts – 27 deg C. (80.6 F)
Grapes – 21-24 deg C. ( 69.8 to 75.2 F).
Figs - 23.9- 29.4 deg C. ( 75-85 F).
Do not forget tissue damage for most temperate fruit will occur at temperatures over 30 deg C. (86 F)
Temperatures either side of the optimum will also work, but the percentage take will be reduced. See graph below for walnuts.
Callus graph showing optimal temperature range
I had no idea they were considered easy to root! Three of the four cuttings have green leaves, so I will baby them. I assume any successes will be full-sized trees of unknown disease resistance. It’s an interesting experiment!
I think the general consensus is that they are not. I think the variety or rootstock that Dennis was using is an exception, and perhaps there are many. Also, his climate is low stress for late winter and much of spring. Overcast, cool, lots of rain.