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How Long Will Untreated Wooden Planters Last?

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Wondering about your options in raised garden bed materials?

Wooden planters, built out of untreated wood raised bed garden materials, will probably last much longer than you think. Yes, untreated wood will decompose over time. But, because it is untreated, you reduce the risk of potential toxins moving from your wooden beds into your organic veggie garden.

Hooped wooden planter Raised Bed

Raised Wooden Beds are Ideal for Season-Extending Greenhouse Hoops

It’s true. Treated wood for raised garden bed materials is controversial.

There are plenty of articles and studies indicating that more modern methods of preparing wood to withstand ground contact has eliminated the potential for toxins to enter the soil from them. And, I’ve also read that should toxins leach into the soil, most plants won’t do anything with the toxins — implying that if the soil is toxic, the plants still won’t be affected and neither will the food we extract from them.

But, I’m skeptical about treated lumber for food growing planters.

Plants do any number of chemical exchanges with their environment all the time. When they encounter chemicals they don’t know what to do with or they can’t expire into the atmosphere, they store it away. And a lot of stuff they store goes into the roots. And what’s a carrot or a beet or a potato? Yeah, these are roots. So, I just don’t trust that every plant will remain unaffected by a bunch of maybes in raised garden bed materials.

I’m one to follow my gut instincts on these things, and my gut tells me to err on the side of caution. So, I prefer to spend a bit more money on untreated cedar (in the PacNW) for my edible garden raised wooden beds. Or, better yet, I might select juniper for my raised garden bed materials. That’s because juniper boards are often made from invasive species trees. So, in my estimation, the cost in those initial purchasing dollars is, to me, much less expensive than the potential health and environmental costs of taking another route.

Rotting Raised Bed Material Board

Cedar Board Rotting Over a Decade After Installation

So, how long will those raised, untreated wooden planting beds last?

The photo shown here was taken in the summer of 2011. This board is one of many in a set of raised wooden veggie beds we had used intensively for over a decade before the photo. And, this board was the one to decompose the most first.

Unlike the other raised bed building materials in other parts of the garden, this example board had soil and plant contact on three sides of the board — interior to the raised bed, on the ground below the bed, and opposite the raised bed where it was lined with ornamental Carex to edge a walkway (see photo at top of page).

This wood gave us over a decade of growing food year ’round before rotting.

Too, a nearby tree had invaded this bed and done damage to the board as well. Moreover, as you can see, we had compromised the integrity of the wood a bit more by affixing brackets on the exterior of the boards. These brackets were important. That’s because we used them to slip in PVC for hoop houses.

And, no, the PVC does not make ground contact on these beds.

Would a board treated for ground contact have lasted longer?

Probably a raised bed material made out of something treated would have lasted longer. But, once it did begin to rot, I wouldn’t be able to compost it.

Would a treated board leach toxins that may have made it into my food?

Maybe. And, again, I’m not into maybes when it comes to growing food in my raised beds.

Can cedar raised bed materials leach toxins?

Perhaps, but those naturally occurring toxins scare me a lot less than the man-made ones. Plus, given that cedar chips are in most composted mulch in these parts, odds are I’d have the same issue going on in my purchased amendments as well.

Can I recycle this rotting board?

Sure! In fact, years later, this entire raised bed eventually composted in place. That’s great! It fed the soil, which builds the environment for plant roots.

But, it took several years before this tired, hardworking piece of lumber stopped holding up all of that raised bed soil.

Can you teach me more about choosing wisely for my garden?

Absolutely!

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48 comments on “How Long Will Untreated Wooden Planters Last?

  1. Brian Mountain on

    I understand that there are variables, but how long could I expect PT lumbar to last in a raised garden bed, especially if I water sealed it prior to adding dirt?

  2. Garden Mentors on

    Brian, We don’t tend to use pressure treated lumber in raised (food) gardens. And, we also avoid using sealants on wood. While these may seem safe to some, for us, erring on the side of caution is the direction we prefer to take. Certainly, you could talk with your material vendors to get their inputs, and perhaps studies, on the materials you’re considering. Good luck!

  3. Barbara Finlay on

    I bought an old wornout dresser with some good wood drawers. I want to use these as planters. I have drilled holes for drainage. They are old enough that even the bottoms are wood, unfinished. I am hoping these last a while, because they make nice ready-made planters for my herbs.

  4. Garden Mentors on

    Barbara, Thanks for sharing. One of our client repurposed old drawers as planters, and it turned out beautifully. Keep in mind, that an old dresser may have finish/paint/glues that aren’t ideal for food growing situations. You may want to consider using the drawers for ornamental rather than edible plantings. Good luck!

  5. Betsy Berger on

    I want to grow organic tomatoes in a planter because the retirement home that I live in sprays herbicide on the grass. I am having a difficult time finding something that is really food safe that I can afford, since I am living on a retiree’s income. I looked at pottery planters that are glazed the the outside, but they all have glaze running into the inside, and to me the glazes look like they are lead based.

  6. Shane on

    @Betsy Berger
    I use earthboxes. They are usually like 50$ each but last a very long time. I’ve grown tomatoes in them and they seem to love it. You can grow 2 in each according to the instructions and since they have unlimited water they both grow huge. The only thing is you have to watch your soil since blossom end rot is much more common. I not my reply is late but I never seen it till today. Next year 🙂

  7. Franky on

    I am in the process of building a vegetable garden bed. I have read about using a mix of beewax and oil to protect the wood. However, it seems like that may be for other-than-cedar lumber. Do you recommend using that mix if I will use cedar?

  8. Nallely Mejia on

    As a general rule, how deep and wide does a planter need to be for veggies? I have bell pepper, spinach, strawberries, broccoli, kale, currently on small planters but will be transition them soon. Need to know if small planters will be ok for them since I don’t know if their root system gets really deep if shallow

  9. Garden Mentors on

    Nallely, Thanks for writing in. There are different depth requirements for different crops. If your planters are on earth, and roots can extend into the soil, then you have added depth that way. If they cannot, then you need to determine the depth requirement per crop. Since you have such a wide array of foods listed, there isn’t one depth. Spinach, for instance, can grow in about a 6″ depth planter okay. some of your other crops will need more depth. Plus, there are many cultivars of each of the foods you’ve listed. Some have been developed for small planters. Some need much more room to grow. So, really, there isn’t just one “rule of thumb” to go by unfortunately. Try researching your specific varieties of each plant for grower recommendations. Good luck!

  10. Thomas on

    I built 3×5 garden boxes out of untreated pine in 2016. They need to be replaced at the end of summer. So I got 4 years out of them. They were sitting on the bare ground. I will probably do the same thing again except sit them on an inch of gravel. Cedar is about 5 times the price.

  11. Merry Peniston on

    We have some lovely old stained doors from a 100 year old house. Would thE old glue and old stain still leach into the soil?

  12. Peter Kowal on

    Hi, I am looking at having a raised planter made to be the same height as the wall at the rear of my house. It would be approx 26’x 2’6″ and 2′ heigh so will take a bit of filling. Its beyond my skills and from the quotes I have one have recommended railway sleepers, and the other 4″x1″ (not sure which wood) which they assure me will be fine. I was concerned about the weight that it would have to hold and if 1″ timber would be strong enough. Have you any thoughts/advice. Thanks in advance.

  13. Garden Mentors on

    Peter, Sight unseen we’re not really able to get into specific project recommendations. That being said: a 26′ is a long run and will likely require quite a bit of bracing. And if the 4x1s are actually truly 1″, that might be relatively flimsy. Railroad ties doused in creosote really aren’t our choice ever. Good luck!

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