how to construct arbor posts in the ground without concrete

If you wanted to build an arbor without the use of concrete or treated wood, and wanted it to last for a while, what would you do? Bury the posts and treat the ends in some way? Bury a metal pipe or post of some sort that the wood can be bolted to? They would need to be proof against wind uplift or blowdown.

Well, there are two ways that I can think of. One is the species of wood used. If you have access to black locust, that will give some serious longevity to the posts. The other is to treat wood posts with a solution of borax dissolved in water, then spray or submerge the ends into the solution allowing the wood fibers to absorb the borax and then let air dry before use. (That's not my idea, I learned about borax as a wood preservative from fellow permie Redhawk) :)

And yes, your idea of burying a non-rotting material that the wood post can be bolted to is another good technique.

I've started back filling holes with stones,gravel,etc.
I've been doing this in buckets above ground,as well as in holes.
Promotes drainage,saves me from using cement, concrete  etc.
I've considered adding boric after the posts are already in use by drilling holes and filling them with boric acid paste.

Gilbert, maybe you could design them to incorporate the idea of Rock Jacks?

Permies thread here.

Maybe even have benches on each side as one of the pictures shows ?

You could burn the ends of the posts that touch the ground so that they would last longer or place them on flat rocks .

Hi Miles,

That might work. I'll see if I can design them in.

William, I thought about backfilling with gravel. One thing I'm wondering about is whether the post would pull out of the ground.

James, I'll probably be treating the posts in any case. I wonder how quickly the borax will leach out?

Gilbert, thats a good question. I have no idea how fast is will leach out, or even if it will leach out at all.

Guys, if I have learned one thing from Travis on here (I hope I have learned more than that) it is that fenceposts need to be driven in anywhere you have frost heaving. I think the gravel backfill will do nothing to prevent degradation from carpenter ants/termites (they just need a small entry point) but will tend to be very difficult to firm in. If you at all can, I would either use charred wood or treated, driven in. If you can get black locust or osage orange, you are a lucky dude/dudette.

Ti, that's what I was worried about. Termites are not a big problem here, but we do have carpenter ants. And since this is an irrigated garden, the dry climate won't help.

And in addition to frost heave, I have a clay soil and since this is an arbor, there will be wind and snow loads.

So far, I think Miles has come up with the best idea. I'll be using cedar, and if I can incorporate some sort of Rock Jack, that should work. Maybe I'll build a gabion wall or bench with rebar stuck through the posts so they can't pull out of it.