I agree with John; if you look at the labels on pressure treated wood most manufacturers now stress the fact there is no arsenic in the chemical treatment process.

PS: If concerned about appearance with an ad hoc,
recycled material in a mortared wall around a raised
bed, one can plant evergreen huckleberries (or
whatever appropriately sized low shrub or other
evergreen plant will stay healthy with low
maintenance in a particular climate) around the
outside of it. Good place to grow some heat-loving
herbs, for example.

Treated wood
 

I looked into this a few years ago and after extensive reading. I have concluded.
1. even if using older treaded lumber Arsenic is not take up by plant roots.
2. I would be very careful not to breath the saw dust and remove any generated during building. Arsenic and copper sulfate and the other verious form of copper they tread wood with are not good for you.
3. Untread lumber is cheaper and if paint with tung oil (or paint which is more expensive) it last a long time. Seven years to date and holding the beds in place with little sign of decay. (And that is in the hot sometimes wet south)
Celtic

[FONT=Arial][SIZE=3][COLOR=black]I don't know if this is true:[/COLOR][/SIZE][/FONT]

[FONT=Arial][SIZE=3][COLOR=black]I seem to remember that they used to burn (char) the ends of poles before bury the poles in soil. [/COLOR][/SIZE][/FONT]

[FONT=Arial][SIZE=3][COLOR=black]The carbon coating prevents the wood from decaying.[/COLOR][/SIZE][/FONT]

[COLOR=black][FONT=Times New Roman][FONT=Arial][SIZE=3]dcarch :?:[/SIZE][/FONT] [/FONT][/COLOR]

thats what they do to telephone poles.

If arsenic leaching is an potential issue why not line the part of the wood in the raised bed that is in contact with the soil with thick building/contractors plastic..?

It will aid in moisture retension and also slow down the degradation of treated or untreated wood for that matter. Just a thought.

Red Cedar
 

Use good old west cost red cedar for very long life and now chemi worries.

Around here a 2"x6"x10' treated costs $9.00
A 2"x6"x10' TREX is $54.00
A 2"x6"x10' AZAK is almost $40.00
There are concrete molds available to pour your own 2"x whatever "boards" with fiber mesh and rebar, that would outlast all of them, for a little more than treated lumber.

The new treated lumber used today contains arsenate, instead of arsenic. It is less toxic. It is also highly corrosive to greenhouse plastic. Treated lumber needs to be painted before touching poly.

I read that with the old stuff, root crops grown in pure treated lumber sawdust would get slightly above the government safety threshold, but only on the very tip of the radish or carrot, the part that a person would not eat.

I will be honest I could give a hoot about treated lumber I use it all of the time in my outside projects.
The amount of pollution many people breath in everyday far exceeds anything you will get from treated lumber.
I thought I was going to die when I had to go outside in LA one time.
Landing there looked like we were landing in a BBQ grill but it wasn't BBQ.:(
That's why the rich folks live up in the hills above the haze.:lol:
Worth

Cole, I agree. Paint it.

I wish I had taken pictures of untreated rotten 4" round posts compared to treated 4" posts. One is still usable and the other got termites and then got burned.

I've just used 2x12's. Replaced about half of them over 15yrs. One or two a year is
not a big deal.
The fence posts are 4x4 treated. Beeswax/oil treated the bottom 2 feet.
Paint would be a mess i think. Moisture will quickly get in and start the peeling process
well ahead of wood rot.
I have a wooden boat....very high maintenance.

Beeswax 50/50 oil applied hot will penetrate nicely and harden forming a pretty good
water barrier.

My house is unfinished cedar built '62. My barn is painted and needs it again. Built by us 15yrs ago.

The whole point of my garden, as well as therapy, is fresh clean produce. Rather not count on anyones word as to what is safe. We were crop dusted on the school playground in the 60's with all sorts of chemicals thought safe.

I'm using treated 2x4s ripped into 2x2s for most of my trellising and fence posts. I sharpen one end and drive it with a sledge hammer.

For people on a budget or folks that just want to know or save money there are some options out there that aren't very well advertised.

Lets start with mineral oil.
What is mineral oil yes it is me again talking about the stuff and how much I use it.:lol:
Go to wall-mart tractor supply or any oil distributor and get hydraulic oil.
NOT Hydraulic transmission oil.
Look for an ISO rating like ISO 32 ISO 46 or ISO 68.
The higher the number the thicker it is.
What is it?
Mineral oil, the same stuff used to preserve cutting boards to hone knives with and so on.
Is it food grade no but I can guarantee you it is safe and has little to no taste.
You can get 5 gallons of the stuff at tractor supply for around $30 some odd dollars.
At the same place a gallon is $20 some odd dollars.
Turbine oil is the same thing.
Power steering fluid same thing.
Heat it up and mix your bees wax with it.
The same stuff sold at the store is close to $9 for 12 ounces.:lol:
Amazing what labeling can to to a price.

Worth

Asphalt
 

We have been coating the bottom and insides of raised bed woods with asphalt.It is not water soluble and will not leach.All my bamboo bottoms and tips are coated with Asphalt.Any wood that touches concrete slabs should be coated with a moisture/chemical barrier.

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