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Pressure treated posts for fence, big mistake?

Posted by Nathaniel Bouman 
Pressure treated posts for fence, big mistake?
July 19, 2014 11:02AM
We've got intense deer pressure around here, so a fence is a must for us. We're about to have an 8' high fence installed with pressure treated posts. We're going to be growing holistically and I believe using pressure treated wood eliminates the possibility of organic certification, but a worry fee fence seems worth it. I just wanted to check in to see if folks thought I was about to make a gigantic blunder.

Nat Bouman
Growing cider varieties in Zone 5b
On B.118 at 18X24
Susquehanna County, Pennsylvania
Re: Pressure treated posts for fence, big mistake?
July 19, 2014 11:44AM
It's hard to say and I'm no expert. It has been said that pressure treated posts would leach chemicals in the soil, but I would believe this effect to be within a foot (maximum) around the post... your trees will most likely be like 20 feet from these posts.

On the other hand, even pressure treated wood isn't permanent! What would be the expected life - 10 or 15 years? Would steel posts be much more expensive? Galvanized steel would probably have a better life expectancy than wood without the chemical worries.

Claude

Jolicoeur Orchard
Zone 4 in Quebec
Re: Pressure treated posts for fence, big mistake?
July 19, 2014 05:08PM
The issue with treated posts is not based in science or reality, but in belief and philosophy within the official certification community. And unlike organisations like the Catholics, who have a supreme authority to define truth, criteria for organic certification are left to a large extent to the local authorities to determine. So, the first thing I would consider is whether official certification by one of the certifying bodies is critical to you, or whether simply growing holistically with a respect for nature and avoidance of toxic chemicals, (including "natural" chemicals like nicotine), satisfies your needs.
If you do decide that you need official certification, it is probably worth checking with your local authority as to whether they will in fact withold certification if you use treated wood. (I agree they probably will - this seems to be fairly standard in the community. But it is worth asking, because there are no absolutes.) If so, Claude's suggestion is a good one, and is in fact what I did to fence my own orchard. A couple of cautions: 1) the fence needs to be a full 8 ft. The deer will readily jump anything less than this. In truth, they can jump 8 ft. without much difficulty, but they generally figure that the effort isn't worth it, unless they perceive that your trees are really yummy, or there is nothing else around to eat. An 8 ft. fence requires 11 ft. posts, (probably 12 ft.). These are both more difficult to find, and more expensive. What I did was to get 8 ft. 1 1/4" pipe posts, and plug wood extensions on top, (just 2X2's with the ends rounded to fit inside.) These have lasted fairly well, (because they are not in contact with the soil at all.) 2) If you use any form of hollow metal post, it is critical to plug the top hermetically, to prevent water getting inside. Otherwise, water will accumulate over the summer, and then freeze, splitting the pipe.

Broomholm Orchard
Zone 5b in Nova Scotia
Re: Pressure treated posts for fence, big mistake?
July 21, 2014 10:50PM
Mr. Maxwell,
I don't know where your science or your reality comes from but there is a substantial body of literature that the arsenic in pressure treated lumber leaches out into the soil, moves at a rate of about 1 inch per year through the soil, and can be taken up by plants. Yes, it would take a long time to move from a deer fence to an orchard, and yes, most of the uptake studied has been in vegetables and not fruit trees, but the organic regulations take into consideration wood used in raised beds where vegetables grow to the edge, grape stakes which can be right next to the root system and other uses that bring the very real danger from arsenic in proximity to organic roots.

If you don't care about certification, consider how much you care about poisoning your ground with arsenic, which is still hanging around in soil 100 years after lead arsenate was the main pesticide used in orchards.

We built our deer fence from mostly metal stakes, with redwood posts at the corners. We may have to replace the redwood in 10 to 15 years but by then the trees will be able to withstand a few deer. You do need a full 8 feet.

Fruitilicious Farm
Zone 9b in California
Re: Pressure treated posts for fence, big mistake?
July 21, 2014 11:34PM
Zea Sonnabend Wrote:
-------------------------------------------------------
> there is a substantial body of
> literature that the arsenic in pressure treated
> lumber leaches out into the soil, moves at a rate
> of about 1 inch per year through the soil, and can
> be taken up by plants.

That may be right - I don't want to argue this because I don't know enough in the matter...
However, from what I have read, arsenic is not used anymore in pressure treated wood - at least in N.America. The new formulations use mostly copper combined with other chemicals (which I don't know how bad they are...)
It is intereasting to note however that copper is the main chemical used in there, and that copper is also acceptable for spraying as a fungicide in an organic certified culture...

Claude

Jolicoeur Orchard
Zone 4 in Quebec
Re: Pressure treated posts for fence, big mistake?
July 22, 2014 09:14AM
Arsenic is no longer present in most of the pressure treated (PT) wood used in North America today. However, chromated copper arsenate (CCA) PT is still in use where it will not come into direct and frequent physical contact with people. I've gone on a research binge about PT in the past couple days. I'm not an expert, certainly but I felt like I got the general gist from looking at a bunch of studies. The studies I looked at indicated that arsenic from CCA does not leach that much into the soil, but there will be some leaching--especially in the first year. The studies also indicated (and these weren't PT industry studies) that migration was minimal--arsenic levels above background level were undetectable a few inches away from the source even when the source had been in ground for a long time.
All that being said, I certainly understand the desire to avoid these chemicals and metals. Clearly there are some applications where any leaching or physical contact could create problems.

Nat Bouman
Growing cider varieties in Zone 5b
On B.118 at 18X24
Susquehanna County, Pennsylvania
Re: Pressure treated posts for fence, big mistake?
July 23, 2014 07:24AM
If you want to go natural, cedar has worked quite well for us. Posts put in for animals 16 years ago (eastern white cedar) are still in great shape. Charring wood can add to longevity by thwarting rot and insect attack.

To sidestep whether pressure treated lumber is a health hazard , we have found it does not last as long as cedar. We moved into a 10 year old home and had to tear out stairs and decking, all pressure treated, all old school arsenic laced, and all rotted. It was also swiss cheesed nicely from carpenter ant channeling. So if it will help the argument along, pt does not always do as advertised, and there are natural alternatives that do as nicely. Oh, and check the price difference.

Also, since all materials will eventually decompose, why not use something you feel good about tossing into the landscape when it gets punky?

I also think folks should think more about living fences as an addition to or alternative to manufactured fencing. It has been used with good effect for thousands of years, and unlike the alternative, it gets stronger, not weaker with age.

Walden Heights Nursery & Orchard
Zone 3 in Vermont
Re: Pressure treated posts for fence, big mistake?
July 23, 2014 03:39PM
This is something I've spent a certain amount of energy looking into as well, but since we are looking for posts to replace rotten ones in our dwarf apple trellis system, we aren't even considering treated lumber.

The cedar posts we inherited lasted approximately 20 years in the ground untreated. They were 10'-11', 5" rough rounds, not sure if it was heart wood but likely was as sap wood cedar is more in the 10-15 year range. I priced this out with the area mills and Home Despot and they quoted me a ridiculous $145-185/post! Yeah right.

Spent some time looking at other options and Douglas Fir and Ponderosa Pine are available in that size and fairly cheap $12-25/ post but will last only 3-5 years and 1-3 years untreated respectively. Not worth it.

Two trees that surpass cedar would be Juniper (which I'm waiting for a shipment of out of Oregon at $28 for 10', 6x6"s that may last 25-30 years) and Ship-Mast Black Locust (can't find a source for but that would be best at 150+ years in the ground untreated).

Now, you're in PA and likely Juniper is unavailable to you but I was told by a lumbar rep that Black Locust is mostly available in the SE and you might be able to get some from down that way. It would be a good investment. Or metal as suggested above.

Nick Segner

Wildcat Valley Farm
Zone 8b
Olympic Peninsula Rainshadow
Port Angeles, Washington
Re: Pressure treated posts for fence, big mistake?
July 24, 2014 10:46AM
Speaking of locust..
This is a very quickly growing species. For example, I had placed a 2 foot potted sapling in the backyard 5 years ago, likely less. It grew through the pot, which was set on top of the lawn and is now about 15 feet tall. This is not only a good candidate for harvested posting, but absolutely impetenetrable as a thorny living fence if coppiced/pollarded well. Since it also fixes atmospheric nitrogen, and is excellent bee forage it can likely benefit the orchard in other ways. The barbs have a chemical that aggravates the puncture to an animal. I read in a recent issue of Northern Woodlands magazine that a landowner had to remove a thorn from his head which penetrated his actual skull. How's that for formidable fencing?

Walden Heights Nursery & Orchard
Zone 3 in Vermont
Re: Pressure treated posts for fence, big mistake?
July 27, 2014 09:34PM
Locust is a wonderous wood. Still have some of the original zig-zag split rail locust fencing in the woods around here. 175 years old and still recognizable. Wish I had the time to grow a hedge of the stuff. Looked into using it as posts but couldn't buy any lengths over 8'.
Re: Pressure treated posts for fence, big mistake?
July 30, 2014 04:52PM
Just talked to our local organic inspector/certified and she said using pressure treated posts for a deer fence should be fine. The pt is not involved with production and is plenty far enough away from the trees.
Re: Pressure treated posts for fence, big mistake?
July 30, 2014 06:34PM
Sounds like you found your answer then.

Back to the black locust - I also need posts now and plan to use that fairly long-lived untreated juniper for this go-round but I'm thinking that I'm going to try and get some seed/saplings of the locust and plant a hedgerow of a few now. It'll take them approx 20 years to grow to post size.

Once I replace posts with those, I and my heirs and their heirs will be good for a long, long time smiling smiley

Nick Segner

Wildcat Valley Farm
Zone 8b
Olympic Peninsula Rainshadow
Port Angeles, Washington
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