Chromium in pressure treated wood!

[ajain]

Is it okay to use pressure treated wood to make a raised bed vegetable garden? I read that this kind of wood is treated with chromium, which is toxic. Thanks.

 

[Treeman14]

NO. Do not use PT for a vegetable garden, or for children's playsets. In fact, I'd be reluctant to use PT for ANYTHING. They also contain arsenic. There are some sources for "safe" treated lumber, but its still rather expensive in comparison. You could use naturally resistant would, such as cypress or redwood. Or maybe those man-made landscape stones or pavers.

 

[ArborView]

I would have to disagree here somewhat. Most pressure treated wood is treated with chromated copper arsenate. This is a combination of chromate, copper and arsenic. When this wood is used in contact with the ground, a relatively small percentage of these chemicals may leach into the soil. But because of their chemical composition, they bond very tightly to the soil particles. This means that they do not move easily throughout the soil profile and are not easily taken up through plant roots. Personally, I wouldn't use it for a vegetable garden because of the proximity of the wood to something that will be eaten, but that is about the only place I wouldn't use it, even thought the amount of chemicals present would probably be far from what is considered toxic levels. I would probably make the bed out of regular pine 2x10's or whatever you need, and just put some preservative on them. They won't last forever but it will take a really long time before they decay to the point of not being any good.
As far as using it for decks, playsets,etc., I personally wouldn't worry about it. What I do after installing it is to let it age until it is good and dry, and then stain it and seal it with an outdoor preservative. I think the biggest hazard with pressure treated wood is when cutting it and producing sawdust. This is when you want to wear a dust mask and be sure to wash your hands when you're done working with it.

 

[John Paul Sanborn]

CCA is labled as a Restricted use pesticide.

The EPA is holding hearings on weather to ban it or not, this year they are requiring lables on the products treated with CCA to inform the public that there is a possible threat.

CCA is a highly persistant inorganic compound that disrupts nervous function at relativly low levels.

Paris green, another arcinic compound (copper acetoarsenite) was used as walpaper and paint pigment in the 19th century leading to mental disorders.

Today we have legal battles over lead paint, but we are still using heavy metals in and around the structures we occupy every day.

 

[Treebeard]

Organic Gardening magazine has researched this issue quite a bit & you may find info on their website about it. the EPA has conducted tests on treated lumber & is also a good source of information. I've built quite a few lumber sided raised beds. I generally use untreated 2x6 boards, or 2x8's. I've found that the wood lasts quite a few years even untreated & when you need to rplace the lumber the soil pile stays pretty much in place until you drop a new frame around it. Use screws to hold your bed togeth NOT nails. The wet/dry cycle makes nails pop out quick & the beds fall apart. Deck screws hold better. I've gotten free samples of the "plastic lumber" they're using now in decks & playgrounds, & it looks promising for raised beds. Never rot, basically inert, recycled materials...

 

[Treeman14]

Do you know what the price of that plastic lumber is?

 

[Treebeard]

No idea on price....I'll look for the paperwork in my files... it's probably higher than lumber & add a delivery cost since I've never seen it carried locally myself. But then, look at lifecycle cost of the project. If plastic cost say 25% more but lasted 100% longer than wood....you make out.

 

[treeclimber165]

I made several retaining walls as well as a couple raised beds many years ago when I had my lawn business. I never used screws OR nails to build them. The method I used was 1/2" rebar and a large wood drill bit. They also have drill bit extensions that work well. I would set up the boards, drill the holes straight down through them then beat the rebar down through the holes into the ground with a sledgehammer. I tried to cut the rebar so it extended about 2 feet into the ground. The garden boxes I built for my mom about 10 years ago are still holding up.

 

[Treeman14]

There's no doubt that PT is an excellent preservative for lumber. I built some retaining walls for a commercial project about fifteen years ago and they still look like new. But now they're finding excessive amount of arsenic leaching into the soil in and under PT structures, especially playgrounds. Obviously, this needs more research. But I would prefer to err on the side of caution when it comes to children and/or food.