Hi digs - there have been many discussions on this issue and I have linked several of them below - just scroll down the list for lots of info. It is a heated debate with both pros and cons, advocates and detractors so to avoid another debate I won't post my personal opinion.

The discussions linked for you also contain additional links to other resources, recommendations for alternatives, and details on personal experiences with using CCA lumber.

You will also find a great deal of info on the net - just Google "pressure treated lumber garden". You'll find studies that have been done on the chemical content of pressure treated wood, the soil-leaching debates, planting restrictions and recommendations with its use, and info on the various forms of pressure treating and the chemicals used.

Ultimately we each have to make up our own mind about its use so I hope this helps you.

Dave

Here is a link that might be useful: Pressure treated wood use in the garden discussions

I have tried many types of materials and have found that the recycled plastic lumber is the best. Can't tell you how many types of wood we have used...and replaced...over the last 30 yrs. We used the ioo% recycled plastic lumber last time and it has held up: no rot, no splits, no cracks, no mold...it looks as great as it did when we built the beds in 2000. This produce needs to be staked every 3'-4' when used horizontially (or it will get wavy with the weight of the dirt) as plastic isn't as stiff as wood is. The composite recycled lumber, plastic,wood chips,and resin, is readly available, but I have no personal experience with it. The 100% plastic lumber is expensive, but I think it will hold up for 40+ yrs.

I would err on the side of precaution...have heard not to burn it, I certainly would not eat that lumber so I would not use it near plants.

Not sure where you are but I would hope you can get cedar logs or used bleacher (plastic)seats. The bigger the better. I use clay and rocks on the end sometimes.

My advise is to stay away from treated.

I used pressure treated lumber....I read all the info and made the decision...You have to decide..There are those that will send you nasty emails if you mention you have used PT lumber but doesn't bother me...I post pictures of mine as you will notice..I needed lots of beds if I was going to be able to continue gardening and no one has to eat from my garden except the husband and I...I suspect old age will kill us long before anything that has contaminated a veggie...Here is a picture of my garden and my boxes...at least you can see part of them...they are strong and sturdy and I love them...

{{gwi:113559}}

ruthie, what's that you have on the ground between your beds? Your beds are beautiful!

Current preservation process is not using arsenic.

So, who knows what is worse: treated wood or plastic that can leak who knows what? Best of all possible rocks and bricks.

We've used treated wood. My husband put an extra coat of treatment on the wood before putting the system in place and they seem to be doing well.

When I built my current framed beds 20 years ago, I used PT lumber. At the time, it seemed like the best idea since sliced bread. But after 20 years, I have to wonder just how much is left that can leach into the soil. And the newer ways of treating wood do seem to be a lot less potentially harmful that the old arsenic compounds. So I am a bit conflicted about what to say now.

After thinking on it for a while, I would say that I sure wouldn't re-use any of the old PT wood to make new frames, probably wouldn't buy new PT wood, and plan to replace my existing frames (and the soil within) with either artificial wood or cinder blocks (and new soil).

The artificial wood is not cheap and isn't terribly strong either (thinking of how often I put pressure on the frames while turning the soil to add compost). I think I'll redo my deck tops with it (adding more joists), but use cinder blocks to replace the old PT wood garden bed frames.

And I kind of like the idea of having the holes in the tops of the cinder blocks to plant flowers in all around the edge... I'll have to learn about cementing the blocks together though (an undiscovered subject for me at the moment).

On the other hand, if I had some reason to use PT wood (like having a bunch on hand or a cost consideration), I would line the bed with pond liner (best) or black plastic (OK). That would have to minimize any leaching, I think.

Why not buy your own lumber and treat it yourself safely? Only problem is I don't believe the major players carry the environmentally safe stuff that is soy-based, so you have to order it online.

Pressure treated lumber at the retail level is now copper based and not arsenic, so, I am not sure the old arguments still hold.
I would make a choice based on size and longevity of your beds. If small, use cedar. If large you might want less expensive product.

I received an interesting comment on my blog from someone in the Pressure Treated Wood Industry. He explains the differences between CCA, ACQ and the upcoming MCQ and also what he plans on using in his own personal garden. Perhaps it will help with your decision.

Here is a link that might be useful: Pressure Treated Wood And Gardening

I have been reading about the debate about pressure treated lumber for a while now. My question is, how do we know if what we are buying is the "safe treated" lumber. There is no way to tell, at least with my experience.

My situation is that I did not want to have to rebuild every few years, did not want to use any treated lumber (safe or not), and something aesthetically (sp?) pleasing. So, I used composite decking planks. I admit, there are a little pricey initially, but I will never have to replace them!

Let me tell you, the water drainage/retention is perfect. The soil is never saturated, nor bone dry and the crops have been out of this world.

The way I see it, if you are going to build something, do it right the first time and use the proper materials. That way, you can enjoy the fruits of your labor for a long time with less effort.

I agree that composite decking is the best option, especially for durability. Regarding the question of knowing what is safe and what isn't safe wood, that is not too difficult.
The last time I was at Lowe Depot, the tag on the wood told me exactly what was used to treat it. The person in the lumber area was also helpful in explaining it, and as mentioned before, the old arsenic stuff just isn't for sale at home improvement centers.

ant3eye, Thanks for the excellent link.

Recycle - reuse - repurpose.
I used old tires to make raised beds. I'm preparing a new garden area and I'm going to use tires for that as well. If you cut the sidewalls out and flip the tires inside out noone can tell they are tires. Be forewarned that flipping the tires is hard work - I flipped some and then gave up - once the plants start growing the tires disappear anyway. There's a book about this - Tire Recycling Is Fun - crammed full of gardening tips and ideas for recycling tires. I actually saved money by using tires - where I live there's a fee for dumping them - and my mechanic was happy to give me all the tires I wanted because he saved money too. Just wanted to mention this as an alternative - and the tires last forever. Some people think the tires smell but I never noticed anything like that.

I think every person's situation is different. How big are you going?

I would have looooved natural cedar and applied linseed on it. Better still -- to be able to afford to have a built brick bed wide enough to act as a seat on the edge but I'm not ready to commit to something permanent.

I had considered just plain pine for giving it a whirl for a year or two, and then I came across linkabord at

http://www.kidsgardeningstore.com/13-1355.html

A little pricey, but it meant my 3 year old could help put it together, we could give SFG a whirl, the size wasn't more than she and I could handle, and if I feel like it later I can pull it all up easily and donate it to the kid's play area at my church and get something swankier put in at my home.

HTH!
V.