Pressure treated posts for fence, big mistake?

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

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
Author, The New Cider Maker's Handbook

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

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

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
Author, The New Cider Maker's Handbook

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

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

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

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

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'.

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.

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

Nick Segner

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

Just to add a bit 5 yrs on, charring cedar posts for the in ground collar just below soil level works wonders, I did it 10 yrs ago on young cedars 5" tops, that had large rings, fast growth, and they are not showing any rot. Compared to others dug in at same time, ready to push over.

Old 99 Farm and permaculture site
Dundas ON 5b

I have some experience with black locust and treated lumber as a natural builder and homesteader. While it does fix nitrogen and has some permaculture/silviculture appeal, (the university here did some research in the 30s on developing locust as a grain crop,) it is extremely thorny when young, spreads easily from the roots and seeds, and is quite opportunistic. I would strongly caution anybody who’s considering introducing it to a new system.

Locust is the main thing going in some parts of our woods, (though, like us, it’s “not from around here.”) About 20 years ago the previous owners had all the locust cut and left to rot as part of a state timber management program because it has no real commercial value. The result is that our woods are filled with small diameter (8-10”) suckers and the floor covered with moss-covered logs. In an attempt to knock the vigorous second growth back a bit to let some other tree friends in, we have used quite a bit of locust as fence posts, garden stakes, and compost bins. What we’ve found is that the sapwood rots readily, (that’s where the food is,) and the smaller diameter stuff is mostly sapwood. Even the 10”ish corner posts are starting to show signs of decay at the biologically active soil surface. As suggested, charring would probably help with this, among other things, it cooks out the sugars and hardens the cell walls. When I cut through the moss and rotten sapwood on the larger (12”-24”) logs on our forest floor I have found that most of them are rock solid. These logs also have tighter growth rings which gives them a lower ratio of sap rich early wood to the denser latewood. We’ve drug out the straightest of these to mill for siding, and I can still count on the rest for some emergency firewood when a long winter catches me without enough fuel.

I sometimes use treated lumber in my work as a carpenter, but try to stay away from it. It’s toxic to me, the soil, and the workers and communities where it’s manufactured. The new stuff is less of a problem, but from what I’ve seen, it doesn’t last all that well, either, maybe 10-20 years in contact with the soil, depending on your environment. In Wisconsin I’ve heard that you can still get the “good stuff” if you present yourself as a farmer or commercial builder, but I’ve never wanted to try and find out.

If I were Building a fence and didn’t have the locust that we do, I would try to find the local rot resistant wood, (white oak, cedar, cypress, Osage orange,) order a load of logs, debark them, char the below ground portion, and plant them “upside down,” (a tip from an old-timer in a novel, but worth trying, maybe the cells want to move water in one direction?) I have had pretty good luck calling smaller sawmills by us who make railroad ties out of their white oak heartwood, (white oak 7x9s were $30 for nine footers last year,) but they or a state forester may be able to help connect you with a logger if they don’t have what you need.

FRUIT CIRCUS

SW Wisconsin zone 5a/4b
Homestead/community orchard
2ish acres with half planted in 2018-2019 with heritage apples, alternating b118, antonovka, and seedling roots
Second half planted 2021-22 with plums, cherries, apricot, peach, pears, etc...
SE slope, trees are planted in contoured berms
Native prairie species for all ground cover



Edited 1 time(s). Last edit at 03/26/2021 09:05PM by Prairie Sundance.