Trellis height vs. plant weight

I was just discussing this with someone in chat (hi, Camprn! ) and it occurred to me that I don't think I've seen this mentioned anywhere, though I may have overlooked it.

I built my conduit trellises to 6.5 feet tall intentionally. I'm 6' tall myself, and I figured if I made the trellises 6.5 ft, the plants would probably grow a foot or so taller than the trellis and I'd be able to harvest fairly comfortably (pole beans, etc.) with a trellis of that height.

Well, first of all... if your trellis spans a 3 or 4 foot SFG the way mine did, you end up trying to balance on your boards and reaching up in the middle and hoping you don't fall on or step in your MM, so please don't do that if you can help it.

Second of all... my conduit actually sunk into the ground a bit on top of the rebar. This may be partly because my beds were built on a slope--the upslope upright being sunk in more to keep it level --but my back bed is pretty flat and had the same problem.... the weight of the plants eventually drove the conduit into the ground about 5 inches. (And I do mean "ground".... my trellises were anchored outside the boxes themselves.) I pulled them up repeatedly and they always sank back down again.

SO..... my tentative suggestion is this: You might want to cut your conduit a little long. If you don't have the same trouble I did, you can always pound it into the ground. I would really like to hear if anyone else has observed the same issue.... Have you??? :?:

The electricians conduit strips do a good job of keeping the mounting post secure (they have little tabs on the interior surface that contacts the pipe & gouge into the plastic slightly)

Also if you put a mat (as shown in my pic below), or small square scraps of wood (free) under the base of the conduit, to increase the "footprint" of the distributed weight..... they wont penetrate the ground (Pressure = force/area ...... the pieces of wood make "a" larger, and "P" smaller). Any old piece of wood/metal that's at least twice the diameter of the pipe will work. for each time you double the footprint (in respect the the pipe diameter), you cut the applied/transmitted force in half (roughly).





Here are the conduit straps ... 1/2" and 1" ... metal and plastic work the same (would suggest the metal for the folks up north who get freezing temps).

My conduit trellis has held up amazingly well all summer, even with several butternut squash and all kinds and sizes of tomatoes hanging from it. However, just in the last few days I've noticed a problem in my one of my wide trellis spans which contains the Cherry-Tomato-that-is-Trying-to-Eat-Missouri.

I have two 1' x 8' boxes next a 3-ft. tall hog panel fence. We made a long span of trellis by pounding rebar into the ground every four feet next to the fence to support 6-ft. conduit uprights, then we connected them across the top with 4-ft. lengths of conduit to make one trellis that is 6' x 16'. We tied string from the tops of the hog panels to the top of the trellis framework and it has worked very well. However, one of the middle conduit pieces is sinking into the ground as you describe, but none of the others are, so it looks as though the trellis is sagging at that point. The rest of the frame is keeping it up, but I'm not sure where it would be at this point if it was standing alone.

I wonder if it would help next year to mound some gravel around the base of the rebar before placing the uprights over them? Or maybe place some large washers around the rebar before setting the uprights?

Anything that changes your footprint, or prevents penetration, should help.

For a cheap fix, you probably just need to go to Home Depot and get a Plastic Rebar Cap


Put the rebar cap on the end that you are putting in the ground, dig/poke a small hole in the ground, as deep as you want the rebar to go, insert rebar with cap and then backfill.

For a free solution, just bury a empty vegetable/fruit can, insert the rebar and backfill.

I suspect both methods will enlarge the footprint enough to prevent the rebar from penetrating farther in the ground than you want it to.

I understand the problem described to be that the conduit that is over the rebar is sinking into the ground, not the rebar itself. The same principle that acara mentioned, applies.

If this is the case, then the right size washers would help.

Or a piece of wood, plastic, or metal with a 1/2 inch hole drilled in it, to slip over the rebar for the conduit to set on.

Or, a hole is drilled horizontally into the rebar at ground level for a nail to slide through, and the conduit sits on the nail.

Or, buy a cheapo non-brand name Vicegrip (is 'locking plier' the generic term?) at a garage sale for 50¢ and fasten it to the rebar for the conduit to sit on.

Or, get a straight conduit fitting, attach it to the appropriate blank box cover, and you'll have a 'foot'.

Ahh .... thanks boffer... I misread that....... but yes, "footprint" still applies.

My rebar is full length up to the right-angle-bends & sits very snug inside my PVC, so when one sinks, both sink simultaneously under weight.

Then again, we are all sugar-sand where I live & we have no rock/stone in the soil ...... so everything sinks here (especialy when it rains).

If it were me, to prevent the sliding down of the conduit, I would crimp the conduit just above the end of the rebar, It may work, it may not....

It would work, but you'd have a real wrestlin' match on your hands if you ever wanted to separate them to move the conduit trellis.

[quote="Megan"]Well, first of all... if your trellis spans a 3 or 4 foot SFG the way mine did, you end up trying to balance on your boards and reaching up in the middle and hoping you don't fall on or step in your MM, so please don't do that if you can help it.

Megan:

Instead of putting our climbing veggies on a trellis attached to a 4X4 or 4X8 SFG we built the trellis on 2X8 SFGs and did not have the stepping in the bed to harvest problem. We also attached the metal condiut to the beds with u-straps. My soil is not overly sandy and we may not have needed to use the straps, but, the straps did add increased support. The straps were tight against the condiuit and may have prevented any sinking into the ground.

God Bless, Ward and Mary.

Thank you, Ward. That is good info!

Fortunately, in the backyard I will have MUCH more control over box size and layout. The biggest general problems, as I see them so far, will be (in no particular order):

• Husband's ham radio antenna (aka the wire clotheslines strung here and there at a height to catch me in the throat!)
  
• Sunlight / shade issue
  
• Tree roots and keeping boxes level-ish
  
• The triffid rosebush
  
• Mosquitoes of Much Hungriness
  
• The lock on the back gate and the French Doors of Doom
  

But that's a story for next year....

I'm a big fan of 2 foot wide beds, it makes things MUCH easier. Dealing with the center of the 4x4 beds is a real pain for us short people

boffer wrote:
Or a piece of wood, plastic, or metal with a 1/2 inch hole drilled in it, to slip over the rebar for the conduit to set on.

I like this idea better than the washer - I'm thinking a used canning jar flat lid would work and wouldn't have the sharp edges as would something like a tuna can lid. It would also have a bigger footprint than a washer. I think next year I'll make enough of these for all the conduit uprights.

Thanks, Boffer and Acara.

Megan wrote:Thank you, Ward. That is good info!

Fortunately, in the backyard I will have MUCH more control over box size and layout. The biggest general problems, as I see them so far, will be (in no particular order):

• Husband's ham radio antenna (aka the wire clotheslines strung here and there at a height to catch me in the throat!)
  
  Megan: Hubby's ham radio antenna would make a wonder trellis for the rappa squash or cukes! Nice and strong and high enough to grow even the tallest vine!
  
  
  
• Sunlight / shade issue
  
  How many hours of sun does/will the SFG's get? 6 to 8 hours are fine for most SFG crops.
  
  
• Tree roots and keeping boxes level-ish
  
  One way to defeat tree roots is to put a solid bottom in your SFG even if it is on the ground. A few drain holes and you are in like flint.
  
  
• The triffid rosebush
  
  Rose bush? No suggestion there.
  
  
• Mosquitoes of Much Hungriness
  
  IMHO there were no biting mosquitoes in the Garden of Eden. Adam invited them in!
  
  
• The lock on the back gate and the French Doors of Doom
  
  Yep. I have been smacked in the nose with French Doors.
  
  

But that's a story for next year....

All gardeners are like Washington Redskins fans. Next year will be better!

God Bless, Ward and Mary.

WardinWake wrote:
Megan: Hubby's ham radio antenna would make a wonder trellis for the rappa squash or cukes! Nice and strong and high enough to grow even the tallest vine!

I think he might have something to say about that, though....

[*]Sunlight / shade issue
How many hours of sun does/will the SFG's get? 6 to 8 hours are fine for most SFG crops.

I have never tracked sun/shade hours back there, so I really don't know. It is surrounded by trees on 3 sides and the house on the other. It DOES get light, but it's filtered/dappled at least some of the time.

[*]Tree roots and keeping boxes level-ish
One way to defeat tree roots is to put a solid bottom in your SFG even if it is on the ground. A few drain holes and you are in like flint.

I am not worried about tree roots getting into the boxes, but the ground is uneven because of them. Some shimming will be inevitable, I suspect... and I agree, I think I'm going to need bottoms on the boxes. Most of the backyard is covered with landscaping fabric already. Will have to talk to dh about it... I am considering doing some TTs, too.

Boffer, thank you for the "washer" idea as well as the bottom fitting for the conduit making feet. I will try it next year. I think my biggest challenge in the back yard will not be the conduit sliding down, but getting the rebar into the ground through the tree roots. Time to borrow a sledgehammer....
:nail: