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I've had my pressure treated wood raised beds for my vegetable garden since 2005 and was recently made aware of the potential risks of using this kind of wood. I have seen conflicting articles saying that it may be ok to use pressure treated wood after 2003 such as this one: http://www.naturalhandyman.com/iip/infxtra/infptforraisedgardens.html, but I am trying to replace my chemical habits with good non-toxic ones.

What type of wood will be good for a few raised veggie beds? About how long do you think it will last before needing to be replaced? I'm in zone 7B if that makes a rotting difference.

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I started this post last night, before submitting it this morning and just saw: gardening.stackexchange.com/questions/3677/…. It looks like from the answers there is Cedar, any other wood suggestions? –  Ann Addicks Mar 21 '12 at 11:39
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13 Answers

up vote 14 down vote accepted

Cedar is the most commonly available rot resistant wood. There is another solution which lacks aesthetic qualities but adds years to the life of wood. Wood rots when it is constantly moist. Here's how to avoid this and use any wood you can get that is not treated:

  • dig a trench about 3 inches wide and six inches deep around the perimeter of your bed.
  • add two to three inches of 3/4 to 7/8 crushed gravel and tamp down
  • start assembling your wooden raised bed
  • on the side of the wood facing the soil line it with an impermeable layer. ( I happen to have some pond liner left over which does a great job but you can also use 40 - 60 mil plastic sheeting used for covering insulation. This plastic should last five years if covered.)
  • place your wood and liner in the trench, back fill with soil and you are done

Other materials to replace wood include stone, used paving stones even empty wine bottles!

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Thanks for a great answer! I never thought to use pond lining! –  Ann Addicks Mar 21 '12 at 16:16
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pond liner is wonderful. It stops weeds that spread by roots from coming into your backyard from the neighbours. It is costly but is stable outside for over 25 years. –  kevinsky Mar 21 '12 at 16:33
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@kevinsky's answer is very good if you want to keep edged raised beds.

Another thing to consider is that "raised beds" don't need any kind of edge. They're mainly for aesthetics -- which might be important to you, but aren't necessary for the plants. Unless you have a need for very high beds, you can simply mound up the soil. My garden doesn't have edges around the beds. Every spring I rake some of the soil from the paths and mound up the beds. The paths get compressed by foot traffic, but we never walk on the beds so they stay raised.

I've seen people use regular untreated lumber (i.e. spruce/pine/fir) for raised beds. It lasts 3-4 years. If you are anywhere near a real lumberyard (not a big box store) or sawmill and you can get cheap, rough-cut, possibly second-quality boards, and you don't mind rebuilding beds every few years, it may be cost effective to just build with this. (Use @kevinsky's drainage tips to extend the life.) Since they're natural and untreated, when they start to rot and need to be replaced, you can break up the boards and bury them under your raised beds. They will compost slowly over the course of several years -- no waste!

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Thanks, I assumed that the raised beds would erode if done in mounds. Great mention for the lumberyard, I'll have to check that out! –  Ann Addicks Mar 21 '12 at 16:18
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@AnnAddicks: They do erode a bit, but like I say, if you just mound them back up with a rake when you're doing spring garden chores it's not a big deal. –  bstpierre Mar 21 '12 at 18:04
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Check out juniper! It lasts longer than cedar or redwood without any chemicals, plus it is an invasive species in Oregon. Cutting it helps to restore the grassland ecosystem -- no old growth forests need be clear cut to obtain this stuff!

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Constructed 3 large raised containers 5 years ago using green oak and have found this to be a successful material. I was looking for a very solid and long lasting material. The raised boxes are 4' x 10' x 2', using 2" thick cut material. A few problems I found with green oak included the weight and the density of the wood. So make sure you have access to a good pick-up truck available and a well built assistant. Another important necessity will be good tools, because you will not be able to securely sink a nail into this material. If you want to use nails, you will first need to drive a screw with a smaller diameter than your nails into the wood then remove the screw and sink your nails. Needless to say we went with screws and make sure you use a fully charged power screwdriver. I built these 3 boxes for approx. $300. .

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I build my raised beds out of 2x12x8 boards of Douglas Fir framing boards. They will last over a decade. I live in Oklahoma, zone 6. Do not use treated wood for edible gardening - unless your consumers can tolerate arsenic and cyanide in their diets!

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Cedar, redwood, brick, cinder block. There are limitless options. The keys are durability (rot-resistance) and safety (won't leach poisons)

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Here in the rural northeast, rough-sawn hemlock is a popular choice. Cedar is also a good choice as is redwood. Try to get heart-wood if possible. I have had garden boxes out (with ground contact) for one season and can see the dry-rot starting on a few of them. Isolating the wood from ground contact is important and the gravel idea outlined above looks like a good one although, if you aren't in a really wet area, maybe just putting the beds up on a few flat rocks, like what is used for a stepping-stone path would help, too.

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Just to add a few notes about my experiences:

Southern yellow pine lasted 3 years. SYP with linseed oil applied the first year added another year to its life, maybe.

This year I built cedar boxes similar to how Ana White did them here. Though mine were 50% more expensive each. Still not bad.

I have 30 or so Black Locust logs 8-10' long 3-15" in diameter some of which I'll be building some "Lincoln Log" style beds this year as an experiment. Black Locust is quite rot resistant and makes great posts.

Douglas Fir is better than SYP. A box I made from DF was good for 5 years or so.

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This was very useful. After reading this post on the false economy of cedar raised beds (nwedible.com/2011/02/raised-beds-and-false-economies_18.html) I've been going back and forth on my plan to use cedar. Think it might come down to lazy factor. Don't want to rebuild too frequently. I've read other claims that linseed and tung oil only add about a year. It's nice to have confirmation. –  OrganicLawnDIY Sep 8 '13 at 21:39
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I wanted to use cedar but didn't want to pay the premium. I found a good article about using cedar pickets, so I built mine like this.

http://ana-white.com/2010/05/hack-natural-rustic-cedar-raised-beds.html

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Do not use pressure treated wood esp not for leaves or nut they are high in mineral like arsenic, calcium, etc. And while it may only leach out x amount under normal conditions. You are instead sending roots into them adding water to them, even giving allow the leached water to rain away easy so that more can be leached again. You are also adding nitro and phosphates which will react and dissolve the toxic chemicals even faster.

Good eatings.

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Don't use timber. Use earth-derived aggregate. See http://www.lulu.com/shop/claude-lewenz-friends/how-to-build-a-raised-bed-garden/ebook/product-17502895.html (download is free) for detailed instructions including engineering plans to make the molds. No rot, last for decades if not centuries, snails have a hard time climbing up them, sun heats them extending the growing season by about two weeks, they look beautiful and of course, they are non-toxic.

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Hi and welcome to our community, it looks like you might have an association with the link you've posted, I'd just like to mention that our policy for this site is that if you have an affiliation with a link you post that you merely disclose it. Other than just mentioning this this looks like a good answer. Thanks! –  wax eagle Aug 25 '13 at 17:26
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Cypress hasn't been mentioned so I thought I'd throw that out there. It has very good decay and insect resistance.

Cypress has the approval of Burton Guster II.

Henry Spencer: So what kind of wood are we gonna use for these bookshelves, Gus?
Burton 'Gus' Guster: Uhhh... cypress.
Shawn Spencer: Cypress? Really?
Burton 'Gus' Guster: It's a good wood. It's what Noah's Ark was made of.

:)

It's also the wood that is currently being used to make raised garden bed kits sold by Square Foot Gardening.

You may also want to look into concrete block. Smaller blocks such as 4x8x16 seem to be the right size as do some of the concrete edging. Cost per linear foot is cheaper than the expensive, naturally decay resistant wood and it lasts a lot longer. Cons are it's a little harder to install properly it might not be as pretty depending on your tastes, skill level and ultimate design.

There are some concerns about using concrete due to the additives. I've read conflicting information on the subject so I encourage you to do a search and come to your own conclusion if you use cement blocks.

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You could also use stacked cinder blocks if you don't want to worry about the wood rotting away. Plus you get extra pockets for plants on the side if you stack the cinder blocks with the holes up.

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