Pressure treated posts

[Frieda]

I have some melon plants about 2 feet away from some pressure treated posts. Are the melons OK to eat? Someone told me the wood leaches arsenic into the soil. True or baloney?

[senegaltictac]

Yes the wood does leach arsenic. As for them being safe, they are probably not any less safe than plants treated with pesticides. If your program is totally organic except for the treated wood you are probably OK. If you are still using pesticides and other synthetic chemicals many of them will be in higher concentrations and many of them are more dangerous than arsenic.

[khwoz]

Along these same lines, what would I use to create raised garden areas? Do railroad timbers contain arsenic and are they bad in any other way ??

[drchelo]

I found some "logs" for raised beds in the Gardener's Supply catalog that are black rubber - made from recycled tires. These boards are molded to fit together and you can make a 3X3' , a 6 X 3' or any multiple of three - foot sizes to fit. They also make a wonderful drip irrigation system for these beds. As far as I can tell, these boards do not break down or succumb to sunlight damage like ordinary plastic or rubber, and they are easy to assemble. The online catalog is at www.gardeners.com, if you want to take a look.

[senegaltictac]

Railroad ties contain creosote, same thing used in telephone poles. I don't know how much leaches out but creosote does kill plants. If you use a chainsaw or other saw to cut them wear long sleeves and a dust mask. The creosote will burn the skin eyes, and nose.

[Enzyme11]

KHWOZ wrote: Along these same lines, what would I use to create raised garden areas? Do railroad timbers contain arsenic and are they bad in any other way ??

They use coal tar creosote to treat rr ties, but that doesn't mean they might not have CCA, arsenic, or heavy metals in them also. Coal tar creosote is a pretty bad product in its own right. It's carcinogenic, it leaches into/contaminates the ground water, and it just isn't a good thing to have around or work with. The groundwater and on-site contamination from the creosote treament industry has been fairly bad and is pretty difficult and expensive to clean up (often with public money), so that's not an industry that deserves much support in my view. There's plenty on the Web about the adverse effects of coal tar creosote and the creosote industry if you want to learn more about it.

Don't use wood unless you want it to decompose as part of an overall treatment or as a way to use timber from your own property. If you must use wood, branches or logs cut from pruning or tree removal would be a good choice and maybe untreated scrap lumber or dissasembled pallets if the size fits (with the usual caveats about using diseased wood from trees with seriously contagious diseases and maybe using an extra dose of beneficial nematodes in the area if you're unduly worried about additional termites). If wood isn't treated, it won't last; if it is treated, it won't last forever and you don't want it around the garden. (Also, as an organic gardener, I don't want to contribute a nickel toward the wood treatment industries by buying their products.) Other than marine or aquatic applications, I can't think of a common home use in this country that exposes wood to more decomposition pressure than using it in garden retaining walls -- especially in organic gardens in warmer climates. Treatment merely retards decomposition -- it doesn't petrify the wood -- so the treatments will come out sooner or later. That includes wood treated with the quat ammonia products. There are so many better non-wood choices. Stone or concrete would be good choices in most cases, and the recycled rubber or plastic products would be good also if the cost is workable. Depending on the design, soil type and where one is in the country (heavy snowfall/cover might be an issue, for example), one may not need any barrier to make the beds. That may be especially true after roots develop in the bed to help hold it together. The Dirt Doctor knows a lot about using raised beds, so maybe he'll chime in on the topic.

[khwoz]

Thanks everyone for replying. Enzyme11, what are QUAT AMMONIA PRODUCTS ?? After reading these posts, I think I will use concrete, cinder blocks or wood from the trees I cut down.

[Enzyme11]

KHWOZ wrote: Thanks everyone for replying. Enzyme11, what are QUAT AMMONIA PRODUCTS ?? After reading these posts, I think I will use concrete, cinder blocks or wood from the trees I cut down.

My spelling wasn't so good -- it should have been quat (quaternary) ammonium. Anyway, a prevalent replacement for CCA (chromium copper arsenic) wood treatment has been ammonia copper quaternary (ACQ) compounds, which usually are a varying combination of quaternary ammonium or amine, ammonia, and copper. Of those, I'm least crazy about the copper, but I'm suspicious of what quat compounds might be used also. I believe the ammonia mostly is present as a carrier, but I don't know if the copper is in the cuprous or cupric form. The ACQ technology may be somewhat proprietary, and it seems to be a step in the right direction from the so-safe-for-so-many-years-and-yet-so-dangerous CCA. (Some in the forum may not know that the Dirt Doctor went out on a limb as an early and quite correct opponent of CCA wood treatment, for which he received undeserved criticism then -- and no apologies now, I imagine.)

Ordinary ammonia is NH3 with an overall neutral charge. Quaternary ammonium is NR4+ with 4 "R" groups bonded to the central nitrogen atom, and the overall net charge is +1. The R groups could be a lot of things; if they are methyl groups (CH3), then that specific quaternary ammonium molecule would be a tetramethylammonium ion. Whatever associates with that ion makes up the rest of the molecule; a halogen like bromine or chlorine with their -1 charge is an example. Quaternary ammoniums or amines can have widely varied physical characteristics, depending on what the R groups are and on what is/are connected to those R groups. Two broad categories of quaternary ammonium compounds are surfactants on the one hand and biocides on the other. QA compounds are common in hospital disinfectants, and they can be pretty severe materials. The physical nature of quat ammonium/amines gives/can give them a chameleon quality. One of the first commercial consumer examples of quat ammonium product that I remember (at least I think I remember) was the combination shampoo and conditioner products -- Pert, I believe, is the earliest one I remember seeing.

[Nadine]

drchelo wrote: I found some "logs" for raised beds in the Gardener's Supply catalog that are black rubber - made from recycled tires...

I believe the rubber from tires is not that good for the soil. The chemicals they contain are not exactly food grade. They will leach out. My brother is a chemical engineer who works with stuff like this. (I often shudder when we talk about his work).

[HarryGardner]

Hi- I just heard about "ACQ" last night on "This New Old House" or something similar title-wise...

The wood looks the same as CCA. I checked a websearch, and found the EPA's comments and the official treated wood website, designed for producers of the product, as well as checked the MSDS.

I didn't do a side-by-side comparison of this MSDS with the CCA's, but they certainly look similar enough. I did a search on DD.com, and there is no mention by Howard. Why isn't anyone talking about this yet?

Since Dec. 31 2003 was a deadline for CCA product removal, I anticipate a major push by the wood industry for this product, and to tell us how much safer it is....I don't believe it.

Meanwhile, thousands of ranchers and land owners are burning the "cedar" on their hill country land.....

[Nadine]

I did a search on Google and found quite a bit. I will take it to Howard tomorrow. He has a lot on his plate right now, but I feel sure he will address it once he has done research to his satisfaction.
I thank you for bringing this to our attention. :wink: