Yes the easy heat brand has different models of heat tape. The one I described and the thread is working with is silver with metal braiding on the outside and has no tstat. There is a picture posted here somewhere. Won’t let me put a link up
Kind of bionic if you will. It can be used to winter graft in cooler areas indoors like garage or basement. Not outdoors or in a cold frame. The one you show here has the thermostat attached as you found. These usually activate at about 35-40F.
If you wish to be able to output more heat, try a model designed as a de-icer for roofs.
This one puts out 5 watts per foot of wire but I think that I have seen them as high as 7 watts. Combine it with a thermostat of your choice (I have experience with the programmable automatic Inkbird models) and that should be a lot more functional than a wire that puts out diminishing heat as the temperature increases, such as a self-regulated wire such as you described:
Thanks for the input. Had not considered a deicing cable. Sounds more like what I need. Already have the inkbird so YAY!
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And the Easy Heat de-icing cables come in all different lengths. I have ordered one that is 120 feet long to use for another project of mine, but they come in various lengths. The shortest I’ve found is 20 feet, and I think the longest I’ve seen is 240 feet.
I have a variety of persimmon and mulberry rootstock/scion dormant in cold storage. Would success rates drop drastically if I pulled them out and grafted right away totally dormant on the callus pipe? As opposed to waking the rootstock up slightly before grafting.
Also is it realistic that they could have enough time to callus on the pipe and then I could put them back in cold storage till threat of frost has passed? I’m just worried about rootstock waking up and then I don’t have any good options for frost protection after I graft.
No need to wake up rootstock before hot callusing.
In fact it’s better if they are asleep. You could even hot callus and put them back into cold storage if you ensure that the scion doesn’t wake up.
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It’s my first year grafting and I wasn’t entirely sure whether to go with cold callusing (my garage will stay 50’F - 55’F for the next month) or the DIY Hot Pipe. But I figured I’d want the hot pipe for when my persimmons come later, so I might as well try out some of my first grafts in each system (about half cherries on mahaleb, half pears on OHxF87, a few quince/medlar on Quince Provence.
I tried to doofus-proof this by adding the furring strips as shown below, and placed some pegboard on top just because it was running a bit hot and I wanted to avoid getting the grafts too close to the cable. I’m not really sure why I didn’t get the exact cable suggested by @barkslip but one said it would hold soil at 77-85’F so I picked it up. I put a Govee thermometer in the pipe so I could track the temps on my phone and I’d advise this if you’re not sure what your temps will look like (especially if you’re not using the exact cable/temp environment as @barkslip). Initially, before adding the pegboard, it was running 100+ and still rising (see the first spike). After adding the pegboard, it ran to about 95’F. Finally, after adding the probe at 81’F I had temps pretty much stable +/1 a couple degrees. The Govee runs a few degrees hotter than the probe just because the way it sits, but throughout the graft area the temp is between 75’F and 85’F.
Here are the completed grafts that had enough scion to go into the hot pipe, my knife work was much worse than it had been in practice but hopefully a handful take!
As @ramv mentioned, dormant is preferred for hot callus on persimmons. It’s equivalent to letting fig cuttings grow roots in the dark on heat mats. You want the callus to form and heal the area you performed surgery on while the rest of the plant stays asleep. That’s why Dax suggests keeping ambient room temperature in the 50s.
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About six weeks ago, I decided to make my own hot callus pipe (HCP) to callus my grafted standard gooseberries. I changed the initial setup described above a bit because I had limited space (lengthwise). That’s why I’ve placed two shorter tubes in parallel. The proposed heating cable isn’t available here, so I ordered one with contant power (+/- 10 W/m). The maximum temperature the heating cable can reach is +/- 40 °C. Because this is to much (system is well insulated), I used an inline LED-cord dimmer to set the desired temperature. And once set at the desired temperature it will not change much if the surrounding temperature is more or less stable (otherwise the setting can be adjusted a bit). There is also no switching on and off like there is when using a thermostate.The heating cable is attached above an XPS insulation strip by covering it with alu-tape. Using the alu-tape the heat is better spread over the whole tube, ensuring a more stable temperature inside.
Another minor change I’ve made, is that I use slits that are wider (+/- 1 cm). So I don’t have to push on the tiny scions of the gooseberries to place them in the slits. The opening is then covered with a piece of insulation that I removed to make the slits.
Because the heating cable is very flexible, it’s also very easy to adapt this parallel setup if needed, to an inline setup by modifying the wooden support.
Below some pictures of this setup.
As you can see on this picture, the grafted scion/standards don’t touch the cable. The temperature of the heating surface is only a few degrees higher then the temperature needed.
PS.: The real dimensions are +/- 10 cm X 3 cm X 4 cm (L x W X H)
Jack
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I’m gonna make a callus pipe today. I’ve read most of the thread but I might have missed something. I have two questions:
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I see the warning to keep the scion off the cable. Is there a material (e.g., fiberglass insulation) that I can safely insert above the cable and below the scion to guarantee separation.
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I see the strong suggestions from @ramv (excerpted above) that when grafting persimmon, the callus pipe should be used on dormant scions and from @Barkslip that the apparatus should be kept in cool (e.g., 50 F) ambient temps, so the scion stays dormant while the callus forms. Is that the consensus?
#2 is quite a shift from the advice (without a callus pipe) to graft persimmons only after the rootstock has leafed out. This contrast suggests to me that the critical variable is the temperature of the graft union, which would be higher later in the growing season, not the growth. Does that make sense to others?
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Yes, you want to put both scion and rootstock back to sleep after callusing so they wake up like a new Frankenstein tree in spring.
Yes, growth or sap pushing doesn’t mean grafts will succeed. You’ll get tons of growth here in the PNW in spring but grafts won’t callus at these low temps.
People conflated growth and temperatures as it worked at their location.
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I have wood that has a groove cut in it that was used for shipping banded pipes. That groove keeps the cable close but not touching the tree.
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The way I think about it is the tree is ‘waking up’ at only the heated location. without the rest of it needing to wake up to help heal. Hence the 50° F recommendation from Dax to maintain dormancy for the rest of the tree. Also dark. I’ll be using my Pittsburgh shower room or my garage depending on the weather forecast.
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Bingo. Thanks.
Got it. As @ramv says, people conflated growth and temperature. I had been hearing advice framed in terms of growth. I just wanted to make sure that this was a misinterpretation of the dynamic.
Thanks both.
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Thought that after years of reading everyone’s great ideas and feedback I ought to throw out an alternative I use, which is an old Chest Freezer as a hot box and that I get very good results with on all Juglans. I’m in England and summer bud grafting isn’t reliable here so winter grafting of Juglans/Carya and other hardwoods is the only reliable solution.
I’ve tried hot pipe systems like those above and also enclosed beds with a similar insulated tube with the whole rootstock/scion covered in damp peat moss etc.
I’ve found the biggest issue is keeping the humidity high and constant so the scion doesn’t dry out, this Jan/Feb I’ve been at 60-80% take on walnuts on juglans regia stocks, most of which are 12-18mm (1/2"-3/4") diameter.
The heating cable and thermostat wire are just hung around the inside and I use damp perlite around the rootstocks, I’m testing whether to cover the whole scion with it, making sure it’s not too damp, plastic bag over the top which ensures about 90% (ish) humidity.
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The only downside is that after callusing at 12-14 days it can wake up the scion so I transfer to a mini tunnel in a tunnel with no additional heat, if it drops below -5C I’ll probably need to do a bit more.
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if you are worried bout the graft contacting the heat cable, I would suggest putting a hardwood dowel in there to keep some separation and act as a spacer, you could use any material really, but an appropriate sized dowel would probably be easy to use, or just cut a strip of hardwood with a table saw or something, however thick it needs to be to keep your graft about centered in the pipe.
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FYI, based on initial indictions, my experiment warming grafted persimmons using a hot callus pipe seems to be a success. See my post here:
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After only 22 days, 8 of 12 persimmon grafts placed on the pipe have broken bud. I’m 1/1 with Taishu, 2/2 with H-118, 3/3 with Chuchupaka, 2/3 with Dar Sofievki. That leaves 1 DS and 3 Cardinals. I’m pretty sure there’ll be more takes soon. I’m considering this a big success, in both numbers and timing.
And so, I’d like to thank Dax @Barkslip for promoting this method and Ram @ramv for encouraging me to try it despite my skepticism.
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