I was looking at the pictures from January and wondering if those worked. Sounds like so far so good.
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Hello, i just finish reading this really interesting thread! And i have a difficult question. Do you think this setup could work using it in a wood cabin without insulation in France? 
Of course i’m not waiting for a yes or no… The problem seems to be big temperatures difference between day and night. So the pipe could be too cold at night. So do you have any idea about what i could try to make it work. Like putting coats around? Or putting straw bale around and something else on top? And one last thing i would like to graft wallnut.
Thanks a lot for your advices!
If you read Dax’s initial post, he specifically says NOT to graft walnuts with this method. He’s grafted many thousands of trees, I’d listen to his advice. Research other methods for walnuts, they’re available on the forum.
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on this thread post 273 someone said this: “Just had a long talk with Cliff England from Englands nursery, he did many thousands of hot callus grafts back in the 90s, various walnuts, heartnuts, pecans and chestnuts, really everything, here is his tips. Walnut rootstocks must be conditioned before grafted or will bleed and fail, even while dormant! He advises, 10 days to 2 weeks before grafting, dessicating rootstocks by placing roots in dry compost, then after this “conditioning” graft, put in the tube for 21 days, keep roots in dry compost the whole time or will fail. Start hight on rootstock, if fails to callus, cut it lower and try again, at some point it will stop bleeding and take. He said he wasted a few hundred rootstocks before figuring this out, then did thousands with 90% success. Season, late winter into spring, continued into a cold bot AC cooled shed into april to extend season of hot callus.”
So i think it’s possible that’s why i’m trying to understand…Thanks
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Walnut grafting - #2 by Fusion_power This is likely the route and advice I’d recommend for walnuts, but let us know if you choose the hot callus route and have success!
Thank you! I wasnt succesfull searching on the forum… I think i don’t know how to use correctly the search engine
My makeshift hot copper recirculating line callus pipe for a bunch of Prunus on Krymsk86. Space saver style. Great thread full of ideas. My recirc pump is on for about 20 hours a day.
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Been reading this interesting thread and want to thank all for helping create an effective cost effective winter grafting solution.
This heat tape thing you are perfecting is a real good idea for us hobby guys. Growers like hot water because it is entirely consistent and they do volume so it pays.
The “self regulating heat tape” is kind of a misnomer. It regulates based on outside temps. It averages 3W per foot at 50F. Can go as high as 6W if real cold. It is not designed to get too or stay at a certain temperature in fluctuating outside temperatures as we do need but just to keep pipes from freezing. It self regulates by using a resistive material between the 2 conductors in the cable that changes density and conductivity with temp. Neat stuff! Thus it only gets as hot as is needed (to thaw pipes) at any spot on the cable and no Tstat is needed. To get to the desired consistant temp with SRC in our application (for which it was not designed) you will have to place the entire calousing structure in a location where the surrounding temp supports the capacity of the cable to get to that desired temperature within the foam tubes. Garage or bsmt is probably in ball park That can also change depending on amount of insulation. Some of you are seeing this now. The higher the surrounding temp the more likely it will get there. IE at freezing surrounding temps it will not be able get to the desired calousing temp in the suggested pipe structure but would still thaw pipes nicely. As you build your structure you should consider this and perhaps experiment first b4 going all in. The caveat with warmer temps being needed outside the calousing structure is that it tends to wake up the roots over a certain amount of time, depending on variety cloned. Kinda shoots the whole purpose in the foot. For sure It can and does work if you can get the outside and inside structure parameters you need or add insulation without too much trouble. After all the ease reliability and low cost of SRC vs hot water is what interests us.
I see we can increase the temp somewhat within the foam for colder outside conditions by doubling the heat tape within the pipe. This may also exceed desired temps. That does cost more and it isn’t cheap heat cable nor is a tstat to control the extra heat. The cable warms and lays flat in the pipe so it doesn’t take up much more room than a single. Messing with extra insulation is also an option I guess but where are we going with all this?
I think I will use a soil heating cable with a dumb tstat attached in future structures like this. Hopefully I can find a soil warming cable without a tstat that I can use with an aux. tstat to control would be nice. This would heat to a set temp and supply accurate wattage needed regardless of outside temp. These are also a lot less expensive.
We have here a good concept and useful structure but alas self regulating heat cable is not ideal or very flexible for some uses. Can work good if in the right spot I guess.
I suppose all is known somewhere. Probably not as much fun as here though.
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I am not quite sure that you’ve got the correct method of operation there. When my cable for building a hot callus pipe arrived earlier this week I wanted to test it right away and make sure that the wire functioned correctly. Just for giggles I plugged it in to an outlet inside the heated house and let it run for about an hour. It was still cool to the touch. Then I unplugged it and I took it out to the garage. I placed the thermostat portion (that which is circled in white)
inside of the freezer section of the fridge/freezer in the garage, and then plugged the heating cable into an extension cord. About an hour later I came back and picked up the long black portion of the wire that was outside of the freezer and it was amply warm, confirming for me that the thermostat is in that overmolded portion of the wire.
If you have any question, feel free to look over at another thread that confirms this function:
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You’ll notice Dax mentioned an ambient room temperature range for which one should use the materials he specified. Freezing or hot rooms are not what his design is made for. Other strategies should be used outside the parameters specified if one is unable to maintain the desired conditions.
For me, the garage is just about right, and a room closed off in the basement used to be alright. Now that I have a heat pump water heater I could put this setup near that area of the basement as it keeps the temperature cooler (or I could duct that air towards my callous pipe).
No I didn’t see that mention. People that use this that way seem to be content. I use it in a cold frame so not the best for me.
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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