Here are some samples of trellises, posts with iron bars and concrete wiring, A frames, posts with wires... the fruiting plants at the center are all done with single posts, iron bars and concrete wire baskets:

Various pictures from the day:

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Oh, and here are some pictures of the two dragon fruit I have in the back yard, one is finally flowering and fruiting a bit after it's third year, the other I just planted three weeks ago in a new trellis:

My three year old, Guatemalan red:

My new trellis for a variety called Purple Haze:

Both trellises were made with $5 treated wood posts from Home Depot. Seem to be working so far.

[1] What is the groundcover you have around your trellis, is it hay? or cut grass from your lawn?

[2] I notice you have both a triangular and square trellis, why did you change from triangle to square?

[3] How deep does each leg of the trellis go into the ground?

[4] What is the length of the short horizontal segments?

[5] What soil do you grow the DF in and what fertilizer do you use?

[6] I also have several plumerias, they flowered over the winter under my grow light, but since then no flower, what do you feed yours?

Thanks again, much appreciated!

1) I use grass clippings for everything, great mulch decomposes quickly and builds the soil, can't see throwing it out. I've heard that dragon fruit really respond to a thick mulch of dried grass clippings so we'll see.
2) The triangular trellis was a first try. Afterwards I came to realize I wanted a bigger more spread out structure, hence the larger rectangular approach.
3) I made it with large tall tree stakes from Home Depot. I think each stake was about 8 feet tall, pounded each about 2 feet into the ground. After years of growing back there, my soil is pretty loose so a sledge hammer did the trick.
4) I think the front horizontal segments are about 16 inches long, the side ones are about 12.
5) I live in coastal Orange County CA, in the flood plain of the Santa Ana River. I'd guess the sediments washing down from the mountains around here probably go down deep, a mile or more. Add many years of adding organic matter, mulches, grass clippings, it's a pretty loamy soft organic soil. Fertilizer wise, maybe a handful of 15-30-15 granular fertilizer once every six weeks while growing, and that's about it.
6) I'm a bad one to ask about plumeria. I'm so close to the coast and it's been so unnaturally cool and overcast this summer that most of my plumeria have mildew and only really spurt into growth and have normal leaves during the rare weeks when we have a stretch of warm, drier, sunnier weeather. Pretty rare so far. Do you have yours out in full sun? that and the same 15-30-15 once every six weeks, about 2 tablespoons per 5 gallons of pot is all I use.

Good luck with it ;)

My plumerias are in full sun, but I think I overwater them. I need to learn how to control that water hose 8-))
The farm store at Cal Poly Pomona has a bunch of huge potted plumerias for sale, I felt the soil, and they were all dry. Mine's never dry, so I guess that's my problem. Thanks for all the answers.