Dragon fruit trellis guestion

[Plantinyum]

I am planning on making a trellis for my df plants, which I will be planting in the ground in the greenhouse. I know people do make them from concrete poles and I have found thinner ones which will do the trick for me , but need to make the tops on which the plants will be spreading and hanging from. I want to make the tops also from concrete ,like make a mold for them and then cast the together with the pole to make them fuse.
Now the question, is it okay to use a freshly casted form for the plants to grow on, the pole part will be cured and will not release any major chemicals, but the top will be fresh .....anyone has experience ?? Thank u for yall's comments !!

[wonderfruit]

I do not know. I saw people covering the concrete with hemp fabric

[Ulfr]

They grow fine on the fresh concrete. If you are making concrete supports make sure you have plenty of reinforcement through whatever shape you make.

I made my posts out of concrete but my tops using a PVC pipe/cap (same size I had used for the concrete mould) with steel through it to make the frame and cemented for stability on the inside of the pvc post topper.

Here is the only pic I have on my phone but on the less mature posts behind you can see the toppers on the concrete posts.

[spaugh]

you should let the concrete cure for a few weeks then it is strong enough to use.  otherwise theres no issue with DF on the cement.

[pineislander]

I made  posts and cast disc shaped tops with 4 holes for DF stems to emerge through. It took about 6 months for cuttings to reach the discs and they had no problems with fresh concrete, within a few months the DF stems were sending roots downwards. In my opinion wrapping DF posts is a waste of time. The roots, even on trees, are sending them down to soil, so your inputs should go into soil, not on the posts.
 A friend made this video showing my DF posts and tops @ about 15:00 minutes:
https://www.youtube.com/watch?v=MuY3Dewhr7U&t

[Kuhyay]

I’ve had great success with this design and will use it when I scale out my planting.

Standard rebar provides more than enough support now that these are mature

[spaugh]

kenny, where can I get the top mold?  ive got posts with the smaller top tip section but havent made tops because the mold was going to be difficult to fabricate.  i wanted to do one like you have. 

[Plantinyum]

Thank u all for the vids , pics and suggestions!! I was thinking I can cure the fresh cement part in a vessel with water for a few days after it gets hard and strong, but may not do this if they are ok with the fresh cement....I will probably make the top square form, since it the easiest to fabricate, I really like Kuhyay's trellis design. Will def use some kind of stiff wire for  reinforcement , thanks again to everyone .
Will keep u updated on the project !!

[pineislander]

I’ve had great success with this design and will use it when I scale out my planting.

Very elegant design how the top slips over the post!

[Kuhyay]

kenny, where can I get the top mold?  ive got posts with the smaller top tip section but havent made tops because the mold was going to be difficult to fabricate.  i wanted to do one like you have.

Hey Brad, I cobbled it together with some window blinds for the circular part and styrofoam for the cutouts. The foam bits are wrapped in duct tape to prevent sticking. I’m happy to chat with you more about how to put the forms together!

[Kuhyay]

I’ve had great success with this design and will use it when I scale out my planting.

Very elegant design how the top slips over the post!

Thank you pineislander! In practice though, I found my spacing to be a little off, resulting in some wobble and instability. I added some epoxy and that sorted it out. I was able to hang on the top part without any movement. I’ll probably play around with this part of the design of the post in future versions.

[Kuhyay]

Thank u all for the vids , pics and suggestions!! I was thinking I can cure the fresh cement part in a vessel with water for a few days after it gets hard and strong, but may not do this if they are ok with the fresh cement....I will probably make the top square form, since it the easiest to fabricate, I really like Kuhyay's trellis design. Will def use some kind of stiff wire for  reinforcement , thanks again to everyone .
Will keep u updated on the project !!

Reinforcement is 100% necessary.  Concrete has great compressive strength, but very poor shear and tensile strength. Wire mesh would work well. I happened to use some standard rebar.

[Plantinyum]

Thank u all for the vids , pics and suggestions!! I was thinking I can cure the fresh cement part in a vessel with water for a few days after it gets hard and strong, but may not do this if they are ok with the fresh cement....I will probably make the top square form, since it the easiest to fabricate, I really like Kuhyay's trellis design. Will def use some kind of stiff wire for  reinforcement , thanks again to everyone .
Will keep u updated on the project !!

Reinforcement is 100% necessary.  Concrete has great compressive strength, but very poor shear and tensile strength. Wire mesh would work well. I happened to use some standard rebar.

cool , I like it very much , I will draw myself a project on paper, to have the measurements and such for the styrofoam cutting . Mine thought will not have the part that connects like lego to the pole ,since the poles I have do not allow such connections ..
The reinforcement will be connected to the top of the pole , and casted together with it, dunno if I explained this appropriate ...in my mind its clear as a sunny day  haha 😅

[spaugh]

kenny, where can I get the top mold?  ive got posts with the smaller top tip section but havent made tops because the mold was going to be difficult to fabricate.  i wanted to do one like you have.

Hey Brad, I cobbled it together with some window blinds for the circular part and styrofoam for the cutouts. The foam bits are wrapped in duct tape to prevent sticking. I’m happy to chat with you more about how to put the forms together!

Nice work!  There's a place in India called RCC that makes basically the same tops.  They have metal forms that you can toss around without the form breaking etc.  You can flip it over and dump the wet concrete and make loads of them.  If I decide to make one of these its going to be metal so I can make 50 or more tops and not have to be careful handling the form. 

I have a welder and other tools to make it, its just been low on the priority list.  I did plant out about 15 posts with no tops and they seem to be working ok just using rope also but the tops are a nicer solution.  It looks better and its easier to get the vines to hang from a proper top like you have. 

If you are interested in making a better form from steel as a joint project let me know.  I need some motivation to do that.

Heres the tops from RCC which I'm sure you have already seen.  They have videos of their process on YouTube including video of their steel forms. 

[Jagmanjoe]

Once one piece is made the way you want, spray it with mold release for urethane and themyou can use urethane resin to pour over it in a box.  Once that cures, flip it over, pull out the original and then just continue using mold release on the mold itself and pour the concrete in, let it cure and then pull it from the mold and reuse.  There are specific urethane resins that work particularly well with concrete and, if wanted, you can use standoffs to hold steel rebar in position to reinforce the concrete before pouring.  The right resin will have a lot of flexibility to pull the completed concrete part out.  Just be sure to coat the mold with fresh mold release each time before pouring the concrete.  You can even embed bolts into the concrete for mounting the pieces if you want. 

I used to have a mold casting business and made a lot of parts over the years.

[Kuhyay]

kenny, where can I get the top mold?  ive got posts with the smaller top tip section but havent made tops because the mold was going to be difficult to fabricate.  i wanted to do one like you have.

Hey Brad, I cobbled it together with some window blinds for the circular part and styrofoam for the cutouts. The foam bits are wrapped in duct tape to prevent sticking. I’m happy to chat with you more about how to put the forms together!

Nice work!  There's a place in India called RCC that makes basically the same tops.  They have metal forms that you can toss around without the form breaking etc.  You can flip it over and dump the wet concrete and make loads of them.  If I decide to make one of these its going to be metal so I can make 50 or more tops and not have to be careful handling the form. 

I have a welder and other tools to make it, its just been low on the priority list.  I did plant out about 15 posts with no tops and they seem to be working ok just using rope also but the tops are a nicer solution.  It looks better and its easier to get the vines to hang from a proper top like you have. 

If you are interested in making a better form from steel as a joint project let me know.  I need some motivation to do that.

Heres the tops from RCC which I'm sure you have already seen.  They have videos of their process on YouTube including video of their steel forms. 

That’s awesome! I’d definitely be interested in taking a shot at making some permanent forms together.

[Plantinyum]

Heres what I did till now, its not very symmetrical but will do the work for me , now just need to find a flat surface to mount the pieces on in a way I can easily remove them when taking the form out , I need to get two to tree tops from this ....

[K-Rimes]

I really like the look of those concrete posts. Maybe one day when I have land I'll do them all that way...

[Plantinyum]

Heres the ready mold, I was wondering if I could use cooking oil for the non sticking agent???

[Kuhyay]

Vegetable Oil, motor oil, or some specialized mold release agent all are good choices. Your form looks great! How do you plan to attach it to the post?

[Plantinyum]

Vegetable Oil, motor oil, or some specialized mold release agent all are good choices. Your form looks great! How do you plan to attach it to the post?

the post will be placed in the center of the thing and casted together. Will be a challenge to make it stay still and leveled but will figure this out, planning to cast it inside home since its cold now outside and i'm impatient to wait ...
Will just have to figure out also something in the center, probably a cement piece to lift the pole a little so the solution can take hold better to the pole ...

Its complicated that way and if it doesn't work in the end I will try to make them the other way with the connection part , still not late for that ...

[Seanny]

You guys are making great supports!

[Plantinyum]

Heres the first top I casted, I really like how it turned out. I figured out I will secure it to the pole with rebar pieces which will be hammered trough two sets of holes both on the top and on the pole, it has rebar as armature in the form also..the empty space if any will be filled with liquid concrete ...I think it will be sturdy enough ...
I will wait two more days for the cement to harden and will take out the form in the elements to start the chemical leaching process ...