I use concrete blocks. Because of their smaller size, its easier to arrange them in any shape you want AND they don't leak any poisons into your vegetables.

Good idea. old bricks, tyres and roof tiles are also good.

I've read that the shredded tire mulch should not be used in a garden as it leeches toxins into the soil. I dunno if that's true for non-shredded tires.

I don't use pressure treated lumber myself because the study results seem to be mixed, depending on who's doing the study. But why take the chance when there are other easy alternatives, I say.

Hi;
I use Pressure Treated for several raised Beds, I lined mine with Heavy Plastic, Open at the Bottom. I have a book on greenhouses and I used the thickness they suggested and then put 3 layers overlaping the seams, I used Stainless Steel Staples from the Home center so they wont react with the copper in the wood. New Presure treated uses copper less dangerous than arsenic. Caped the top I am careful not to puncture and replace every 3-4 yrs. I feed the Greens & Herbs to a rabbit shes doing fine. It would poison her long before me.
Keith

No idea about tyres leaching, but people use them whole all the time here, particularly for potatoes (stack them 3 high).

I also use foam boxes from the grocer as an edging:

{{gwi:290809}}

(The foam boxes are rendered with cheap path dirt mixed with a little bit of cement - that gives them a sort of vaguely rock like surface, which grows moss in winter)

Or you're both being poisened slowly and don't know it yet. Either way I wouldn't chance it.
Why would you line the beds with plastic if your not worried about using ACQ? Doesn't make any sense.
Ceder isn't that much more the ACQ. Especially if you add up the cost of the plastic your too.

mylu, my thoughts entirely. Inert substances like concrete, old tiles, polystyrene and PE film are probably best for a veggie garden.

Hi all! Just passing through, drooling over your greenhouses. We discussed this very topic under the Potager forum (a brand new forum). See below for the great feedback on the very same question I had also asked. There is a new pressure treated wood on the market but it hasn't hit too many stores yet.

Love your greenhouses and hope to have one someday ;-)

Edna

Here is a link that might be useful: Raised beds

I used 2x10 ACQ pressure treated lumber from Home Depot to build beds last summer. I work in the environmental risk assessment and contaminated soil and groundwater clean up field. I have reviewed the leaching studies and am not alarmed by the findings or lack there of.

jimla: Absence of evidence is not evidence of absence. I've heard exactly the same things said about CCA and creosote.
ACQ may turn out harmful yet.

If you want a safe wood to use, look at http://www.timbersil.com/sst.html Silica is another name for glass.

Maybe ACQ will somehow turn out to be dangerous, but I doubt it. Even though most people said CCA was safe, a lot of us wondered how something with arsenic could be. I think copper is a different story. A lot of the same people that are concerned about ACQ raised beds, probably spray their plants with various pesticides, use weed killer on their lawns, etc. IMO, that poses a much higher risk.

If anyone has concerns about ACQ, they should use certainly use alternatives. I made my beds out of ACQ, but only after spending several hours reading about it on the internet. Even most sites that are generally very much against chemical use, didn't really have much bad to say about it.

Stuart

Home Depot, in our neck of the woods, refuses to cut pressure treated wood to custom size for customers. They claim it's hazardous to employees.

"Home Depot, in our neck of the woods, refuses to cut pressure treated wood to custom size for customers. They claim it's hazardous to employees. "

I can understand that. The fine dust containing ACQ is probably not good to inhale. They could have their employees wear a mask or respirator of some sort, but that wouldn't protect customers walking by.

Stuart

Exactly, Stuart. I figure if they find it hazardous imagine
what is absorbed into veggies *egards!* I went with Redwood.

I suspect ACQ gets a bad rap because it is judged guilty by association (to CCA which contains arsenic). ACQ consists of copper oxide and an ammonium compound. How many of us are changing over our home drinking and bathing water supply systems from copper to polypipe because copper may someday be shown to present an adverse health risk at the concentrations found in our pipes and faucets? Where are we exposed to more copper: daily ingestion of trace amounts in our drinking water or trace amounts in a garden that we eat from seasonally? The ammonium compound may be perceived by some to be a bad thing because it is used in an industrial (wood treating) application when the same compound is used in household detergents and disinfectants. Are we exposed to more ammonium compounds that biodegrade in a healthy, biologically active, compost amended garden soil used seasonally or in higher doses we contact and breath directly as we wipe and spray 409 or Febreze in our homes throughout the year? In the end it comes down to reviewing the studies, the resulting data and making a personal decision. For me, the data supported no adverse risk under my garden use and consumption scenario.

For me, the data supported no adverse risk

Would you like to share your data?

I can find articles calling ACQ into question without even trying (the first hit on google with ACQ):

"Though this preservative mix has proven to be the most effective so far, ACQ poses its own concerns. Similar to its predecessor, ACQ also leaches into water tables and leach tests using ACQ wood in wetlands have shown elevated levels of copper in rainwater run-off, soil and sediment. ACQ doesnt have the arsenic or chromium issues of CCA, but it does have triple the amount of copperÂa substantial increase." -- http://www.nadra.org/industry_news/acqarticle.html

(and that from a body trying to promote ACQ use!)

Saying that quaternary ammonium salts are the same as ammonia demonstrates a lack of chemistry knowledge and makes me doubt the rest of what you are saying.

My (basic) understanding is that ACQ is a wood soluble copper salt designed to bond to the surface of wood fibres. Being water soluble means that it is possible that the copper will leach out into the soil, possibly contaminating it. Copper poisoning is not pleasant, I've had it. You get nasty headaches and fevers and it is very hard to work out why.

Comparing with copper pipes is like saying that sarin nerve poison is harmless because its got carbon in it.

There are two ways to control wood rot: make it poisonous (which will always have the risk of leaching), or make it indigestable/waterproof (such as the silcate technology). Chemicals effective against fungi are generally effective against humans.

"Exactly, Stuart. I figure if they find it hazardous imagine what is absorbed into veggies *egards!* I went with Redwood. "

Dangers from inhalation are very different than from leaching into soil and being absorbed into plants that we eat. For example, diatomaceous earth is favored by organic gardeners for being safe, but it is horrible for your lungs if you inhale it.

Stuart

Nathanhurst:

Would you like to share your data?
I have the same data as you or Stuart or most anyone else these days. It is the information on the web that I researched and reviewed that lead me to my decision to use ACQ lumber. My job involves understanding the degree of risk posed by constituents like metals and pesticides in the environment. When I was looking into ACQ I needed to look beyond the leaching studies that just focus on the copper concentration of ACQ leachate, i.e.: ".but it(ACQ) does have triple the amount of coppera substantial increase." I can agree with that quote to a point. But just because it leaches doesnt mean it is bio available. In the current dialogue, your premise for copper being a concern appears to stem from the mere fact that copper is present in ACQ leachate, period. What appears to be missing is an understanding of coppers fate and transport in the soil from its source (ACQ leachate) through the soil column to a receptor (a vegetable plant root system), the resulting exposure concentration (copper in a tomato) and the frequency at which tomatoes are consumed by the ultimate receptor (us). Soil organic matter, silt and clay particles, cation capacity all serve to attenuate, minimize or limit the migration of copper in the environment.

For me, the data supported no adverse risk
My statement was used out of context in your response since it did not include "under my garden use and consumption scenario". The latter text is where fate and transport and receptor exposure concentration come into play to describe the actual risk posed by copper.

I can find articles calling ACQ into question without even trying (the first hit on google with ACQ):
"Though this preservative mix has proven to be the most effective so far, ACQ poses its own concerns. soil and sediment. ACQ doesnt have the arsenic or chromium issues of CCA, but it does have triple the amount of coppera substantial increase." -- http://www.nadra.org/industry_news/acqarticle.html
(and that from a body trying to promote ACQ use!)

For someone who takes that statement at face value, they would believe it to be a case against ACQ unless they looked deeper into the source. NADRA is the North American Deck and Railing Association whose mission as stated on their website is to "promote outdoor living at its best, in safe and creative environments for the enjoyment of every homeowner". They are not promoting ACQ use anymore than they are promoting redwood or composite decking. The article mentioned is at best a third or fourth order source for ACQ info since its author, a fastener manufacturer, was discussing the compatibility of decking screws with ACQ chemistry. NADRA was however providing it members and web surfers a service by mentioning the ACQ copper study so the user could make their own informed decision.

Saying that quaternary ammonium salts are the same as ammonia demonstrates a lack of chemistry knowledge and makes me doubt the rest of what you are saying.

True, I am not a chemist but I did pick up a few things from my organic chem, inorganic chem, biochem and geochem courses. However, I was not specific enough. I referenced quaternary ammonium compounds in general when I was specifically thinking of DDAC, the quaternary ammonium compound used in ACQ. DDAC is an anti-microbial compound also found in household disinfectants, laundry detergents, fabric softener dryer sheets and swimming pool disinfection to name a few. My point in mentioning it was that DDAC is more common as an active ingredient in products we touch, breath and swim in everyday. As good gardeners we all know that AMMONIA found naturally in high concentrations in raw manures will burn a plant until soil microbes convert it to nitrate, the nutrient plants need. And IF we add too much nitrate-based fertilizer it can leach to groundwater. And IF it reaches a groundwater concentration greater than 10mg/L it can produce methemoglobinemia or "blue baby" syndrome in infants. Organic animal manure.

Copper poisoning is not pleasant, I've had it.

Having experienced copper poisoning first hand its understandable you would be cautious of any product containing copper.

Comparing with copper pipes is like saying that sarin nerve poison is harmless because its got carbon in it.

My plumbing analogy was to point out that receptor exposure concentration (trace copper) and duration (a lifetime of daily drinking/bathing) is equally important in determining risk in addition to the mere presence of copper. Few folks would list pure drinking water as an acute toxin, yet last year in California a young college student died tragically in a fraternity hazing incident by drinking too much water (not alcohol) in a short period of time. The water essentially diluted the electrolytes in his blood and he died of a heart attack. Pure drinking water.

There is a lot of information on the web. Some confusing, some misleading and some conflicting especially when it comes to an emotional topic like human health. I offer my opinion in response to a question by dgriff as to what to make of ACQ. This was my personal decision, based on my review of the literature and my professional experience. Were I a Wall Street type, I would offer my personal perspective on a financial web forum to a non-financial type who wanted to sort out conflicting info about different investment products. Ultimately, its up to the individual to glean what they can from the various experiences expressed here and make an informed decision they are comfortable with.

Ok jimla, I agree with what you are saying there. You sound like you have looked quite closely into this, could you perhaps fill out the wikipedia page:
http://en.wikipedia.org/wiki/Timber_treatment
It needs some expert attention. For example, the exact chemical makeup of ACQ would be useful.

How available is copper in the soil? I guess that if people use bordeaux mix regularly without trauma it can't be too bad. I suspect my bad experience is partly to blame for my knee jerk reaction.

Isn't DDAC highly soluble? How do ACQ treatment prevent rapid leaching?

I do still think that a repellant approach such as silca is a better longer term solution, but you've convinced me that ACQ is probably not so bad. I withdraw my objection.

Here's a photo of the concrete landscape blocks I used to build my raised beds.

{{gwi:290810}}

The raised bed in front of the greenhouse is planted with Citrus trees and the beds in front of it is being planted with plumeria and adenium (desert rose) plants.