What is a good alternative to pressure treated wood for raised beds?

Question

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.

Answer 1

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!

Answer 2

@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!

Answer 3

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!

Answer 4

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. .

Answer 5

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!

Answer 6

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

Answer 7

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.

Answer 8

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.

Answer 9

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.