living trellis "posts"

cousinfloydJanuary 5, 2013

I just put a little pressure on a muscadine trellis post today -- it was a locust post that had been in the ground for about 5 years -- and it broke right off at the ground. I really don't want to use treated posts, but I'm questioning the reliability of locust posts which are supposedly the best rot-resistant species in the area (NC Piedmont), even though I have a lot of other locust posts that are still solid. I've considered planting osage orange trees, but that's a very long-term prospect with plenty of complications. So I've started wondering about ways to avoid posts or at least end posts altogether. What if I just used a couple of established trees for end posts with plenty of daylight in between? A living tree would likely live as long as a locust post would last, right? (And locust posts are hard to come by anyways.) So my question is: what kind of trees would make the best end posts for a trellis (or livestock fence)? I think my ideal tree would be stout, well-rooted, and reliably long-lived, and maybe even serve some use itself (e.g. fruit), but not especially tall and wide (so as not to require as many square feet.) What do you think?

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bamboo_rabbit(9A Inverness FL)


The trees would work but it is a bit inconvenient as the tree would have to be right where you needed it. Why not just use sch 80 steel well pipe? It is what people use to mount their BIG satellite dishes on.

    Bookmark   January 5, 2013 at 7:26PM
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Thanks, bamboo. Although I'm still interested in the far out question, that's a very practical suggestion I wasn't thinking about. I actually have one of those big satellite dishes from the previous owner of my place. Where would I buy that kind of pipe now? Would a single pipe like that well anchored by sufficient for an end post for a long (about 200') muscadine trellis?

    Bookmark   January 6, 2013 at 6:07AM
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Maybe try "pleaching"

Would using concrete footings help stop the rot?

    Bookmark   January 6, 2013 at 8:19AM
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bamboo_rabbit(9A Inverness FL)


The casing is used by well drillers so I would imagine that sch 80 pipe would be available anywhere. If you call drilling companies they may have bent pipe you can buy cheap. It does not matter for you as you are using shorter lengths. Long as the pipe was anchored by a ground line has to be much stronger than say a 6x6 or 8x8 post. If you have concerns you can fill the end pipe with concrete.


I had to look up pleaching:) That would not work too well for grapes due to the annual pruning. Concreting in a wooden post actually makes it rot faster because the concrete holds the moisture against the wood...or so I have been told.

    Bookmark   January 6, 2013 at 9:01AM
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Hybrid willows will grow fast enough so they can support a trellis in two years. But then they would have to be pruned and topped aggressively, a lot of work, with vines getting into the canopy as well. As a matter of fact I am planting a number of them this spring, to support an "invisible deer fence" in a year or so, assuming good growth. I will just top those because I do not care if the fence gets all tangled.

But concrete posts last a lifetime. I have seen them many times in Europe, in fact I think any vineyard or kiwi orchard has concrete posts. Not cheap, probably. For my new grape pergola, I think I will have a piece of pipe sticking into a 5 gallon piece of cement, bury the cement so that 18 inches of pipe stick out of the ground (the peg), drill a hole at the bottom of the pressure treated post, then hammer the post into the peg. Again, this is a pergola, so there will be constraints from the roof part of it against side bending. It would be a less robust design for a planar trellis. The method does separate wood and soil, and the posts should last a lot longer. I have done it for my mailbox, and the wood is as new ten years later.

    Bookmark   January 6, 2013 at 9:58AM
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Scott F Smith(6B/7A MD)

My posts have been rotting at the base. All I do when this happens is pound a $5 metal post directly abutting the rotted post and tie the rotted post firmly to the metal post. The metal post needs to be one of those heavy solid cast-metal ones, not the pressed metal ones, and they need to be pounded several feet down. All of my fixes are holding well so far. Replacing a post completely involves dealing with the trellis wires which is a real pain. I originally started doing this as a temporary measure but now I plan on doing this to all my wood posts - the whole rotting problem is right at the base, the rest of the posts are still good.

I agree with glib that a live tree will be too much work to keep from blocking the light.


    Bookmark   January 6, 2013 at 8:43PM
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As far as live trees blocking light, my muscadine trellis now is just over 200' long, so with that kind of length I could sacrifice a 10 or even 20' radius on either end and still have lots of full sun in between, especially with a north-south orientation and not-too-tall trees at the ends. (Of course, bamboo is probably onto the much more practical answer, but I'd still like to consider the relative strengths and weaknesses of different tree species.)

Scott, were the posts that rotted on you locust?

    Bookmark   January 6, 2013 at 9:16PM
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Scott F Smith(6B/7A MD)

Floyd, my posts are pressure-treated landscape timbers - they are meant for building low landscaping barriers, not for use as posts, and look like a double-thick 2x4 with rounded ends. The posts cost me a couple bucks each at Home Depot, they are much cheaper than real 4x4 or 6x6 pressure-treated posts.


    Bookmark   January 7, 2013 at 9:56AM
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bamboo_rabbit(9A Inverness FL)


It is no wonder they have been rotting. Those landscape timbers are actually the leftovers from the plywood making process. Have you ever noticed all the little teeth marks in them? Those trees get put on a machine that turns them and peels layers off that become the layers in plywood,the same way veneer is made. That is the reason the edges are round. When they get down to the core they are removed and what is left is those landscape timbers. They are then taken and very very minimally pressure treated it is almost a worthless application. The treatment is so weak termites will feed on those posts immediately. Here in ground those posts will last a year max before they fail but we have a high termite population.

The big box stores are no longer allowed to sell good posts....and by good I mean posts treated with arsenic (CCA) they sell posts treated with alkaline copper and the regular treated posts are so so at best. For good posts that will last you need the CCA posts and those you will only find at agricultural supply places as they are still allowed to sell them.

Now before all the greenies start on me......

There is nothing at all wrong with arsenic in the posts if you don't lick the post daily. Arsenic is not easily absorbed by most plants anyway especially if you have normal PH, a balanced soil and a lot of organic matter in your soil as the arsenic is bound very tightly. Don't plant within 12" of a post especially root crops or leafy greens. The use of CCA posts for a trellis, especially the end posts of say a grape trellis is completely safe.

"But as USDA heavy metals expert Rufus Chaney points out, what constitutes an acute toxic dose isn�t really relevant to gardeners. What we want to avoid are chronic toxic doses, which can lead to disease. Chronic exposure means every day for a lifetime. According to the Agency for Toxic Substances and Diseases Registry (ATSDR) in Atlanta, we can ingest up to 0.3 micrograms of inorganic arsenic per kilogram of body weight per day and not be harmed. The average American woman, who weighs 132 lb. or 60 kg., would have to eat more than 18 micrograms daily all her life to see any ill effects. Before you get alarmed, remember this is inorganic arsenic we�re talking about, not the organic types predominant in our diet. And, an ATSDR spokesperson points out, 0.3 microgram is a low estimate for the maximum tolerable dose."

    Bookmark   January 7, 2013 at 11:15AM
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alexander3_gw(6 Pennsylvania)

Floyd, how sure are you that the post was black locust? I have a split rail fence that was installed almost 9 years ago, and the locust posts are as solid as ever. Something fishy is going on here.


    Bookmark   January 7, 2013 at 11:43AM
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I'm quite sure it's the same as the other couple dozen posts I set at the same time. If it was anything else they'd all be rotten by now, right? And even apart from that I'm quite sure they were locust. I got them from a friend that runs a full-time logging business for his regular job and an old sawmill for a hobby-business. Unfortunately, it was the end post (as opposed to a more easily replaced line post) that rotted off at the ground.

    Bookmark   January 7, 2013 at 12:47PM
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Scott F Smith(6B/7A MD)

Bamboo, I've had only four of my twenty cheapo posts rot after ten years. I consider that a pretty good deal for a couple bucks a post, and staking them up I figure I can get another ten years out of them.

Can you tell I have some Scottish ancestry in me? :-)


    Bookmark   January 7, 2013 at 4:37PM
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bamboo_rabbit(9A Inverness FL)


I'm not arguing value....the thing is the posts you bought prior to 2004 are very different from today's posts. Before 2004 those landscape timbers were treated with CCA so of course your old posts are still good. The new landscape timbers can no longer be treated with CCA and instead are treated with alkaline copper. The difference is like comparing a bazooka and a slingshot.

Up north those posts last longer. Here they will last less than a year, the termites destroy them which shows how useless the alkaline copper is on those posts. I have some of them in ground as fence posts. As long as I add borax to the sides of the posts every year they are ok as the borax kills the bugs.

    Bookmark   January 7, 2013 at 5:58PM
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drew51 SE MI Z5b/6a

I'm late to the party here, but saw this old post (no pun intended). I use steel poles used in electrical work to cover exterior wires. Two types are made, well three, plastic ones exist too! Anyway the cheaper (thinner) steel conduit posts are fairly cheap, meant to be outside and should last 50 years or more. I don't need a large diameter post so I use 10 foot 1 inch diameter posts.
I guess if you cemented them in they would be really strong. I just sunk them 4 feet, and put gravel around the bottom before back filling. I drill holes through them for wires.
I just bought four, they were $6.77 each at Home Depot (in electrical dept.) The higher grade poles are super thick and you probably could whack them with a sledge hammer and they would not dent. Overkill and expensive, the thinner gauge posts are plenty sturdy enough.

    Bookmark   April 5, 2013 at 8:52AM
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I think another option is to paint the posts with pine tar before burying them in the ground.... I would paint it from the base to 12" above the soil level...

There's even a "Modern" legal Creosote paint that's still available... (Real creosote is refined from Birch tar, I think....) It's not as good as the old stuff was.. but it also doesn't have all the added heavy metals added to kill fungus either....

Planting trees for posts.... I think the main issue you will run into is the cable girdling the trees over time... My solution was to pound steel posts into the ground to anchor the cables... Gavanized posts seem to hold up quite well.


    Bookmark   April 5, 2013 at 1:46PM
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I just pulled up 30 fence posts to move a fence. Not a one of those posts had rotted in the 12 years they have been in the ground and all will be used in the new fence. The posts were made from 8inch telephone poles that were rejected by the power company. A local saw mill cuts and sells them as fence posts. You would have no problem with these as posts and they are quite affordable.

    Bookmark   April 5, 2013 at 2:14PM
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