Hot Callus Pipe DIY


You can fill a cardboard box with spray-foam and hollow it out when it hardens.


Yeah, I check the temperature constantly, and it is a bit too warm for the optimum of walnuts, which is by the studies 27C/80.6F…mine rises sometimes to 32C/89.6F, mut that is not yet too hot, and it depends on where I stickt the temperature meter. Right now I use a meter that is made for cooking ham :D, works like a dream, I can keep the electronic display outside the box, and check the temperature whenever I want.


Idea, use big chest freezer with precision thermostat, inkbird or like that, set for 40 degrees or so put hot callus pipe or pipes inside, might work with smaller rootstock. of course garage space in winter might be better if available with some heat if needed.


Exactly, I’d bought a bigger freezer if I had the space, but now this smaller one will have to do the job. Two test subjects have been in the pipes for a little bit over two weeks now, pretty soon I’ll find out how well I did the grafts, and if I need to put more moist retaining material in the pipe. I have a fear I did not put enough, and the (walnut) grafts will dry out. But they are wild scions and I can use the rootstock again this same winter, so no real harm done.



Any results from grafting with the DIY hot callus pipe?

I made a callus pipe from above instructions a couple of days ago. The air temperature inside the pipe is only getting up to about 15 Celsius (room temp is 5 Celsius). But if the graft touches the heating cable it says about 28 Celsius, nearly perfect. What do you think, will it work?


28 C / 82 F is nearly perfect or is. I reckon you should check the temperature every couple cm’s for stability of temps and peace of mind. Room temp is awesome.

Even should the cable stay stable and not be too hot along its length, I recommend you keep the unions slightly above the cable.

It works like a champion. Do your thing, it’ll reward you.



Can I use the same temperature for peaches and other fruiting trees?

I’ll try walnuts as soon as the pipe is ready.


Here’s my version. I used a 12 ft Jumpstart soil warming cable so I went down and back. I used a few zip-ties to keep the wire down inside the foam pipe (these are extreme weather zip-ties but I’m not sure it gets hot enough to matter). It took around a half hour for the setup to get to temperature but it stayed in the 77-82F range in a 42F room. I did seal the ends but just with duct-tape. I’m envisioning using one side for grafts and the other for simple callusing of cuttings. Right now I just did cuts every 2", alternating on opposite pipes (I doubt I’ll use all 35 slots on either side as is).


I’ll have (3) of them now. All I gotta do is add the cable for the second 8-footer I’m building. And I have a 10-footer.

So I filled #2 which has 32 slots at 8-foot in length at 3" apart for 4 x 4 inch (any) Stuewe container.

Now I’m going to go “in order”. I’m ultimately growing to sell in 30" Stuewe containers. So here’s that container which I’ll grow seedlings in or purchase seedlings and pot to them or grow my own seedlings in these 14" (white) Deepots, first. I have a lot to learn.

I can pot these also to a 30". These are a 4 x 4 x 14 Stuewe Treepot

I grabbed this big comfy chair that fits in florida homes only and lounged.

Now, today I removed 80 some grafts off the 10 foot. I put them in the darkest corner of my basement. These are mostly nut tree grafts with half a dozen pawpaws and 1/2 a dozen persimmons. (I’ll see how long they decide they’ll stay dormant.)

All these nut trees were grafted on 1-year pecan-seedlings in 14" Deepots and a few on 10" tall mini-treepots I see no need to buy again for what I do. 14" is minimum for pecans/walnuts/persimmon/pawpaw/and if you want to grow peach or plum or any fruit tree. You’re always better to have a long(er) container.

I had some pawpaws cross my hands so I made a graft of each.

my knives are en route to Chicago to have Frank Surace ‘The Art of Sharp’ get me back going again. This coming Saturday I’ll have my knives returned and this newer 8-footer as well as the now empty 10-footer to re-fill.




Dax, when you get those trees growing in those deep pots, do you water them from the top or have the bottom sitting it a bit of water? I’d be curious to hear how you manage moisture for them, as I am challenged in that department.


The answer is very simple: water from above.

If you can and I have in place, hardware cloth for air pruning. Construct any height bench from 2 x 4’s and (possibly) build shoe boxes such as I did. My benches (2 of 3) are sloping massively and from the hardware cloth to the height of the first rectangular shoebox that holds (12 of any) 4 x 4 Stuewe treepot is 9". Go to the end the height of the shoe box(es) are taller. What I need to do so wind doesn’t thrash these things around is build up height upon my shoe boxes. I’ll come up with something inexpensive, I’m-sure.

I know these 30" pots need snug settings and surrounding slots (4 x 4" slots for individual trees) or walls (for the continuation of shoe boxes) of at least 18" tall for me to feel comfortable right from the beginning. That’s my current thinking.



Hey buddy, noticed you are trying to keep moisture in your plants roots. Have you considered using cheap trash bags, like these…
Only a couple pennies each and you can tie them around the stem of the plant, keeping entire root system contained. Something to think about…

They are cheaper than ziplocks, etc… I use them for all kinds of stuff!


No I’m actually bagging the pots to keep moisture off the board. I didn’t lay plastic sheeting over the board but have two layers under it to protect my pool table.

Those are all actually bags I stuffed into more bags anticipating reusing them for other than fresh scionwood bags. I like to use fresh bags when sending scionwood/storing.

I went to Walmart and dove into their plastic recycle yesterday and got hundreds of bags. I also stuff the pots from the bottom to push the seedling up to the top of the container for grafting easiness. So anything plastic I use. I cut strips from my Pro-mix soil bales to stuff in the pots also.

I would prefer a much dryer root-system for grafting but I can’t control that with however many (1000?) containers in my greenhouse.


I’m about to set up a hot callus system similar to this. I have about 100 pecan seedlings ready to graft.


It’s the only way to reliably graft nut trees unless you’re in the field doing bark grafts or flap grafts or whip and tongue with plenty of heat.

Awesome, Darrel.



Has anyone used this for peaches?


My grafting season has started with persimmons in a hot callusing pipe.

(Fortunately?) my rootstock this year was much larger than in previous years so I could not use 4x14 tree pots. I ended up using rootmaker containers which IMO are far better anyway. But I could only fit 10 trees.

I also did 5 more on large rootstock (1/2 -3/4 inch) using windowsill heating mats


Did you have any success with this?


I dried out a lot of the grafts. I only wrapped with parafilm so next time–1. I’ll wrap with parafilm and electric tape and 2. I’ll grab a couple of those thin aluminum bars as @TheDerek used as spacers to make sure the grafts aren’t too close to the wire.


I wonder how it would work to run it through some PEX inside the foam? I totally missed the aluminum spacer in that post, thanks. I ordered a cable today.