Trellis posts of wood, how long will it last

obviously this is variable, but in ballpark terms, I’m thinking of building a grape trellis and if so, I really want to do it once–I am not getting any younger, or more ambitious.

Supposing I did it w/ treated 4x4s in a mixed sandy loam and clay soil, normal to better drainage, how long would the trellis be expected to last?

If not terribly long, what else are folks using for their trellis posts?

Thanks in advance,

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Longer than you will.

We used treated posts and lumber to build a perimeter fence 25+ years ago and it’s still just fine. It will outlast me, I’m sure, which is to say another 20 years.

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Pressure treated wood is great above ground but I wouldn’t put it in the ground. Instead, I recommend a cylindrical cement footing with a metal T post inserted, then use 2 or 3 U bolts to attach the wood to the metal.

you don’t know…maybe I take my vitamins… :frowning:

I guess that’s my easiest route then…thinking of cattle panel and 4x4s sunk deep w/ quickrete in the holes rather than augers coming off each side, etc…


When ever I use any wood that will be on or in the ground, pressure treated or not, I coat it good with Woodlife Coppercoat. really seam to hold up good. Available by the quart, gallon or bucket

I have pressure-treated posts, most of them are still fine after 15 years. The couple that have rotted at the base I just sank in metal posts on either side and tightly tethered wood to metal. I don’t plan on replacing the posts until the above-ground parts start rotting, its not hard to do this quick upgrade on any post getting weak at the base.

Note these are not the fancy 4x4 pressure-treated posts, they are the cheap landscape timbers which are 3x4 or so. They were a third of the price and my Scottish instincts kicked in and I grabbed the good deal.


The posts are most likely to start showing decay where bacteria-containing top soil comes into direct contact with it. In my case that’s only about 12". Anything that inhibits the bacteria will give you longer life, and that’s where the copper could be effective.

“Back in the day” people would dig the hole, line the hole with a plastic bag, dump in some creosote, and set the post. (Creosote treatment plants treated all the timbers used in railroad trestles, telephone poles, and so on. We’re still trying to clean up the mess!) Something similar might be good with the copper- but even a good coat of paint in the right places could help. You could paint it with roofing tar.

In any event, do keep taking the vitamins.


Yes and fill the holes with gravel or sand so the post don’t come in contact with the soil. We do that for sheds here, and it lasts over 20 years. You don’t need to put cement all the way to the top. Here we put them below the frost line which here is 36 inches. I use 8 footers. So 5 feet tall or less. This is to support a shed, and that they don’t heave up from freezing. You could use longer ones if needed. For sheds, they are cut off at a foot tall anyway. So I use shorter wood, 6 footers.

I have 30 year-old landscape timbers in the ground here that are like new. However, that was when they used arsenic in the mix. Industry stopped using arsenic in 2004. Seems like the new stuff rots in 5-10 years when placed below ground without any additional preservative.


If you will paint roofing tar on the posts prior to install or something similar to keep out the moisture your posts will last much longer. I have had good success doing that with my orchard fence

we don’t have a welding machine, so next best thing was to use iron pipes which we primed with rustoleum.
lowe’s will cut the pipe for you, and will thread the tips for free. This has withstood a couple of category-1 wind speeds.

as shown below, when the wood slats finally degrade/warp/crack, they may easily be replaced, by removing the iron cap on each of the 3/8" pipes holding the slats, and just sliding out the rotten wood and then sliding in new ones. Can safely say that the iron posts will last much longer than wooden posts–structurally and esthetically, being resistant to warping and cracking, so cheaper in the long run. The vines adorning it are sponge gourds, btw.


I’ve used these post protectors when building a deck, sounded like a good idea:

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For a trellis for my raspberries I used metal post anchors that you drive in with a sledge hammer and just put the post in the top.
Like these:

You don’t have to dig a hole, you don’t have to worry about ground contact, plus I could use shorter posts since I wasn’t putting 2 feet of them in the ground. I’m not sure if they are as strong/stable as putting the posts in a 100 pounds of concrete, but I was impressed with how sturdy they are. They have longer ones for softer soils.

The best thing is my entire trellis was finished in the time it would have taken to dig a hole, mix concrete and get just one post up the traditional way. I’m not sure if they’d work for your project if you plan on going very high, etc., but they might be worth looking into.

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I have to watch the budget so I went with Electrical steel conduit poles. Many sizes, and 2 grades. I found the cheap grade works fine. It’s thinner steel. I like 1/2 (edit 3/4 inch!) inch poles and they were very cheap too. The higher grade could hold thousands of pounds pressure. The cheaper ones, no, but for my raspberries I have 24 feet between poles and no end support. End support would stop them from leaning in, but I don’t care. 10 feet long, buried 4 feet. Some in concrete, others not. The 24 foot section is not cemented in. Just 4 feet into the ground, 6 feet above.

I like to use these heavy duty line tighteners.

I have 2 more trellis setups. here’s another for beans and cucumbers. 12 feet apart, cemented in. I think these poles are under 10 bucks when i bought them, about 6 bucks. And steel so will never rust. I use para cord for the beans to climb up on. I hold in place with cothes pins. Currently out of the way. Cucumbers were just planted behind the softneck garlic and onions. I grow beans every other year.


Pressure treated posts are available using several different treatment methods. Most of the 4X4 posts from the lumber yard are not intended for below ground use and I expect their lifespan would be 5 years or less. Treatment methods/chemicals were changed a few years ago due to potential safety issue. I don’t believe the new chemicals prevent decay as long as the old ones.

Treated posts for ground contact may also be available and you can tell from the label.

CCA fence posts last a very long time but the chemicals used the treat the lumber may be a concern in a backyard situation.

No 3/4 inch! My bad.

I had some oak posts I used that I got as scrap, they were 2x3 approximately, non treated. Lasted me about 3 years before they started breaking. They are used for raspberries. Going to replace them this spring, thinking about using steel Fence T posts or whatever they are called. I have a pounder so putting them in wouldnt be too hard. Was going to use bailing twine to hold the raspberries up. I cut them to the ground every fall so its cheap and easy to replace every year. Any better suggestions that would be easy to install and last a long time?

Well, lots of different ways to skin a cat! I went the cheap route and cut down a two large red cedar trees in my back yard that I thought was contributing to C.A.R. for the posts for couple of regular trellis and a 24’ x 12’ pergola / arbor. They have been in the ground for 6 years without a problem. Figure that if they ever rot at the ground, I will do as Scott suggested and tether to metal.

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So are you saying that size does matter?


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As I’m about to replace the wooden poles in my grandfather’s vineyard I can comment on their longevity. They are 4-5 inches, non treated, 30+ years old and I’m sure most of them could last a few more years. The wood should be Robinia pseudoacacia (Black Locust).