What kind of wood for raised beds? Composite lumber?

[quelindo]

We're having raised beds put in our backyard & it's a little over twice as much money to use cedar than it is to use regular untreated lumber. Trex composite lumber is about the same as cedar.

We *could* technically afford either, but is it really worth the extra cost? And is composite lumber safe to use in a raised bed for growing food?

Also, what kind of soil mix should I have put in the beds? Is there a formula for the "best" mix?

[kittywitty]

We just used regular untreated wood. It was like $2.50 for each 2"x4"x8'.

[kcstar]

I've got a mix. The first bed I made was untreated wood, but a coworker of mine told me a story about how he'd done a bed with untreated wood and got termites. (And my bed was uncomfortably close to the house.)

I did buy and use some cedar too, throughout the yard, but I focus it most on the beds against the house.

[Quaniliaz]

White oak lasts a very long time. My dad has had white oak beds for 10+ years and they are going strong. The red oak was done after about 5 years.

[goldfinches]

I've only used cedar. Mine that I left at my house I just sold were 5 years old and holding strong - as strong as the day they were built.
My dad worked for years for a sawmill and said cedar would be the best by far.

[tankgirl73]

I wanted to do cedar, but with the number of beds I wanted to do, and all the $$ for the soil mix, we really couldn't justify it. We're talking a difference of $14 for an 8-foot cedar plank versus $4 for untreated pine. I spent about $150 in untreated pine... that would have been about $500 in cedar!

It won't last as long as cedar, I know that. But it's enough to get me started. When it starts to rot, I'll replace it with cedar.

A carpenter friend also told me that juniper is another great option. Just as weather-resistant as cedar, but cheaper. However it's a bit harder to find.

For ideal soil mix, I used "Mel's mix" 1/3 each of good quality compost (5 different types if you can get them), peat moss, and coarse vermiculite. It makes a really nice textured medium, great water retention, and such great nutrients that it's rare to need to fertilize.

I had a few garden flops this summer, but I can't blame it on the soil -- it was a terrible season in terms of weather and I got some blight too. Stuff that grew well despite the weather, grew GREAT.

And I did the potatoes is 100% compost. They grew into like 5' vines, they went everywhere! It was rather impressive! But it was really expensive since I only used really good compost!

[darciedoodle]

We used ipe, it will apparently last 40 years. It looks really nice too. We bought a 60% worm castings/40% topsoil mix and added azomite to the soil. Everything grew really well! We top off the beds with new soil mix every couple years as it seems to shrink down.

[goldfinches]

If you don't get as many made as you would like, and if you don't care if they're all the same, check out the stores at the end of next summer. This summer, Walmart clearanced out their composite board, 4x4 raised beds for $10 each.

[JessicaS]

Mine are cedar but I only get two boxes a year. I have long skinny boxes rather than square.

[bugleg]

I used salvaged Ipe for mine--it has been 3 years with no sign of breaking down at all. Truth be told, untreated lumber will likely last 10+ years.

I wouldn't use plastic or composite, as they are both significantly weaker than real wood. I wouldn't use treated wood for fear of leaching.

[bigteamug]

I have to say, I would REALLY hesitate to use vermiculite anywhere for any purpose. I paid almost 5K to have people in hazmat suits come and suck the stuff out of my attic. And while the companies claim that other mines are not contaminated as the Libby one was, I don't think for myself it is worth the risk of them being wrong. Just because something is natural does not mean it is safe - lead is perfectly natural, so is arsenic....

Please, at the very least, research before you use it. The EPA here is Seattle pulled a bunch of stuff off shelves in garden centers and concluded that some of it was contaminated with asbestos in unsafe amounts. link to paper

google seattle epa vermiculite garden. The link was huge.

The paper is a little dated, but still worth taking a peek at.