7 Ways To Make Wood Garden Beds Last: Nontoxic Sealer & More
There are many benefits to gardening in raised beds or planter boxes: the improved ergonomics, clean appearance, ability to fill them with quality soil and compost, and itβs easier to block out pests. I love raised beds! Yet one of the few drawbacks is that they donβt last forever (and, they arenβt exactly cheap). So, protect your precious investment and follow these 7 ways to make wood garden beds last longer! We’ll talk about how to seal garden beds, lumber choices, drainage and more.
Iβll admit, we never sealed our garden beds in the past. Theyβre made from super durable heart redwood, after all! However, once we moved to our new homestead and began building our βforever gardenβ (and felt the rude awakening of not being in our 20’s anymore during the laborious process) I thought to myself: I want to make these garden beds last a LONG as physically possible.
In fact, we seriously contemplated getting some awesome Birdieβs galvanized metal raised bed kits instead. Those things should last forever! (And you can save 5% with code βdeannacat3β). But in the end, my love for the look of rustic wood won that battle, so here we are: we just finished building 19 new redwood garden beds, sealed and siliconed this time. Do it once, and do it right.
After reading these tips, pop over and follow our step-by-step guide on building wood raised garden beds!
WAYS TO EXTEND THE LIFE OF GARDEN BEDS
1) Choose wood that is naturally long-lasting
One of the best ways to extend the life of raised garden beds is to use quality, long-lasting lumber right from the start. Cedar and redwood are two excellent choices, as they are both very dense and durable. Thanks to their high tannin content, both cedar and redwood are naturally resistant to rot, mold, and insects – including termites. Heart redwood lumber (what we use to build our raised beds) is even more indestructible than common redwood boards.
Garden beds built from untreated cedar or heart redwood can last well over a decade on their own – likely much longer, depending on the climate and other conditions. The 7-year old untreated heart redwood beds in our old garden are still in excellent condition. Iβve also heard stories of friendsβ redwood beds lasting well over 20 years! Then, if you follow the other ways to make garden beds last longer as described below, you can extend their life by several years more.
In comparison, garden beds made of softer woods like Douglas fir or pine can rot out and decay within just a few years. Donβt be tempted to use pressure treated lumber (usually treated pine) to make garden beds last longer either! In addition to containing undesirable chemicals not ideal for organic gardening, the lifespan of treated wood is less than cedar or redwood anyway! Especially when it is in constant contact with soil and moisture – as it will be in your garden.
2) Use wide planks and thick boards
Choosing wide lumber planks is another excellent way to extend the life of wood garden beds. For example, a raised bed constructed out of 2×6β boards will last longer than one made from 2×4βs. Eight, ten, or twelve-inch wide boards are even better! Raised beds are most susceptible to rot in the seams between the boards, where moisture collects and air is scarce. By using wider planks (and thereby reducing the number of seams in the bed overall) it is reducing surface area and places for water intrusion.
The same idea applies to board thickness. While 1-inch thick boards are often more affordable (such as cedar fence boards, which are actually only ΒΎβ thick), the raised bed will not last as long as one constructed with 2-inch thick boards. Plus, thinner boards are more likely to bow or even crack over time under the pressure of heavy wet soil pushing against them. Last but not least, thick 4×4β corner supports will last far longer than using 2×4βs or other smaller wood in the corners.
3) Seal wood garden beds (with non-toxic sealer)
Sealing wood garden beds can help extend their lifespan many years beyond unsealed wood. Applying a sealer will protect the wood from moisture intrusion, mold, and decay. However, you donβt want to use just any wood sealer on your garden beds! Many sealants and stains contain toxic chemicals – stuff you donβt want around your healthy homegrown food and soil.
We recently used this nontoxic wood sealer on our new redwood garden beds. If you know me, then you know I do my homework before choosing materials to use in our home and garden! This particular product is food-safe, made in the US, won’t leach, has no VOCs, carcinogens or endocrine-disrupting compounds, and is nontoxic to wildlife. Plus, it gets great reviews!
We ended up applying 3 coats of Garden Seal to the inside of our beds (where rot is most likely to occur) and had enough left over to do just one coat on the exterior. It goes on milky white, soaks into the wood well, and dries clear with a slightly satin finish. However, the third coat inside the beds did leave a bit of a visible residue, so one or two coats for the exterior would be best. Be sure your wood is totally dry before application.
Hopeβs Natural Tung oil is another nontoxic option to seal garden beds, though Iβve heard itβs best to reapply it annually – which is why we chose the other sealer. This would be a good option to seal the exterior of garden beds where routine application is possible.
4) Seal garden bed seams
In addition to sealing the wood itself, consider sealing the gaps between the boards. Again, wood garden beds are most prone to decay in their deepest nooks and crannies, including the corners and horizontal seams between the wood. When building our newest raised garden beds, we applied clear silicone to all the seams – which is waterproof, inert, and nontoxic once it dries. My friend Steve has been professionally installing and maintaining organic gardens for over 25 years, and he claims that this single step can extend the life of garden beds by 5 to 10 years!
We used a class 50 premium exterior silicone (or this similar option) to seal our garden beds along the inside seams only. Class 50 silicone is far more durable, flexible, and resistant to temperature swings than lower-rated classes. This is important since garden beds are exposed to varying temperatures, and the wood constantly swells and shrinks with moisture.
Use silicone to seal garden bed seams just like you would caulk. First, squeeze it deep, thick, and evenly into the cracks. Then while it is still wet, tuck your finger inside a paper towel and gently smooth it out – removing gaps, air bubbles, and excess. Pay special attention to sealing your corner supports! I also added a dab to any open knots, holes or cracks in the bed interior.
5) Reduce wood-to-earth contact
Clearly, your garden beds are going to be full of soil – so a certain amount of βwood-to-earthβ contact is a given! Yet beyond their seams, wood garden beds are also quite susceptible to decaying along the bottom perimeter. There, they’re essentially sitting in constant moisture. So, another clever way to make garden beds last longer is to avoid setting the wood right on the ground.
Our raised garden beds are perched on top of a couple inches of well-draining gravel. Because we have a nasty gopher problem, we also have hardware cloth and landscape fabric (permeable to water) below our beds. However, that isnβt to say you canβt have the bottom center area of your beds open to the native soil below if you prefer! Iβm just talking about the wood itself.
My pro garden friend Steve installs all his raised garden beds on top of a gravel border, similar to a french drain. To do so, he digs a small trench (about 6 inches wide and deep) and fills it with fast-drying ΒΎβ leach rock. Then the perimeter of the wood garden bed frame sits on top.
6) Shou Sugi Ban garden beds
Shou Sugi Ban is a Japanese wood preservation technique that involves burning or charring wood surfaces. The charring process essentially seals the wood, making the wood more resistant to water and insect damage. Shou Sugi Ban garden beds should last several years longer (or more) than untreated wood of the same species.
To char wood garden beds Shou Sugi Ban style, most folks use a blow torch or propane weed torch. Weβve never done this ourselves, but Iβve heard one drawback is that it does take a lot of fuel and effort. Experts also say itβs important to not burn it too heavily, since deep burns can actually make the wood more susceptible to decay and reduce structural integrity.
This article explains more of the process. This YouTuber also shows his Shou Sugi Ban raised beds here – along with an update showing the inside of his bed 1.5 years after use.
7) Promote good drainage
Good drainage is key when growing in raised beds. Plants prefer fluffy, moist, well-draining soil with plenty of air pockets for exploring roots and beneficial microbes. They donβt like soggy, heavy, compact soil – and neither does your wood! Heavy soils that hold in too much moisture can increase the likelihood of wood decay. On the other hand, raised beds tend to dry out more quickly than in-ground gardens. It can be tricky to achieve the perfect balance!
Fill raised garden beds with soil that is made for containers or raised planter boxes. This article discusses how we create our own soil blend with bulk soil, compost, and an βaerationβ component. Aeration additives include perlite, pumice, sand, peat moss, coco coir, rice hulls, or our favorite: β β lava rock. It promotes that ideal blend of moisture retention and good drainage.
Furthermore, never seal off the bottom of your raised beds with impermeable material, such as a plastic lining. You want your beds to drain freely! I also do not recommend lining the wood walls with landscape fabric, even βpermeableβ and breathable ones. The fabric will hold in extra moisture right against the wood.
Elevated garden beds or those installed on top of hard surfaces (e.g on a patio, driveway or deck) should have plenty of drainage holes in the bottom – just like pots. For instance, we drill at least half a dozen Β½β to ΒΎβ holes in the bottom of our wood wine barrel planters.
And that is how to make wood raised garden beds last as long as possible!
All in all, raised garden beds are a fantastic way to grow food, flowers, herbs and more. I love their sleek look, and for us, the ability to block gophers from getting inside. I hope you picked up a few new tips to help extend the life of your beautiful raised beds today. If you found this information to be valuable, please spread the love by pinning or sharing this post. We wish you the best of luck in building and preparing your beds – with years of bountiful harvests to come!
You may also like:
- How to Build a Raised Garden Bed: Step by Step Guide (with video)
- How to Fill a Raised Garden Bed: Build the Perfect Organic Soil
- Amending and Fertilizing Garden Beds Between Seasons
- Building and Installing a Raised Garden Bed on Concrete (hard surfaces)
- How to Make a Sturdy and Inexpensive DIY Trellis
- Choosing the Best Materials for Raised Beds: Wood, Metal, or Alternatives
32 Comments
Heidi
Hi! Did you sand the wood for the boxes before applying the Garden Seal product?
Aaron (Mr. DeannaCat)
Hi Heidi, we didn’t sand the wood before applying the sealer and it went on really well so I don’t think it is necessary. Good luck!
Heidi
Awesome. Thanks, Aaron. And many thanks to all that you and Deanna teach and share with us all. It’s such a gift. π
Nicola
WOW, These are gorgeous; thanks for the inspiration. You hjave created some amazing gardens. Our school is starting a school garden. We have only asphalt (no patch of soil at all!!!) on which the beds will sit. I’m trying to find the best way to line the garden boxes (7′ x 2′). One option is woven weed barrier (which appears to be plastic). I’m considering burlap which is more natural. Any thoughts on if this will prevent anything from the asphalt leaching into the soil? I’m less worries about soil leaching out, more concerned about things from the asphalt leaching into the soil and plants for our elementary school students. Thanks,
Aaron (Mr. DeannaCat)
Hi Nicola, that is great that your school is going to be putting in a garden! I wouldn’t be too worried about the asphalt leaching or having too much of an effect on your soil and plants. Check out our article on How to Build a Raised Garden Bed on Concrete, Patio, or Hard Surface as it will give you a few ideas that we use when have done something similar. Hope that helps and good luck with the garden!
Judy
I just love reading your articles and watching your stories on instagram. You have a beautiful garden and home!.
We have a 9×9 ground level vegetable garden bed and we normally just amend it each year by adding some sheep manure and a bit of peat moss, however its never as fertile and plants just do ok. I am wondering if the soil mixture you list in this article would be suitable for ours. I really want to remove at least 24″+ of the soil and give it a new overhaul. (btw we are in Ontario, Canada) Thx!
Aaron (Mr. DeannaCat)
Hello Judy, if you have landscape supply companies in your area that offer quality bulk soil, that would be the way to go. From there you could add around 20-25% (to total volume of soil) of quality compost to the soil mixture and there may be companies in your area that offer quality bulk compost for delivery as well. If you wanted to stick with your peat moss regiment, you could add equal parts peat moss, compost, and and aeration additive like pumice, coarse vermiculite, perlite, or 3/8 inch lava rock to create your own soil mix. Sheep manure is a good additive on its own but it would be even better and more complete if it is left to compost with dry leaves, hay, or straw to create an even carbon (leaves) to nitrogen (manure) ratio. Hope that helps and reach out if you have any further questions, good luck!
Judy
Thanks for the quick reply! I forgot to say that the sheep manure we use is the composted one sold in bags. I think this year we’ll finally try organic mushroom compost sold by the yard. And will definitely add in the lava rock you have recommended. I think the aeration portion is what we were missing. Thx again π
Heather
My loving and well-intentioned husband built me a large raised bed out of corrugated sheet metal, but for the inner corners he used lengths of pine only around 1.5 x 2.5. The beds are two feet tall. I’m not sure how these are going to hold up. Would you recommend I ask him to do it over? That will not make him happy!
Aaron (Mr. DeannaCat)
Hi Heather, that was nice of your husband to build you a raised bed. I can’t say for sure if he would need to redo the bed as I am not aware of the entire construction of the bed itself. You can always reinforce the raised bed in time if the corners start to deteriorate, even by adding extra bracing or corner pieces on the outside of the bed. I would just use the raised bed and hopefully if will last you some time and if you need to do something in the future it will be at least a number of years out. Good luck and enjoy your new raised bed!
Caitlyn
We plan to use Shou Sugi Ban and burn the inside and outside of our cedar garden beds. Is it with it to also seal and caulk, or is jut added effort for not much return? We want to have the beds last as long as possible.
Thanks so much for all your great content! It’s been so helpful in planning my garden.
Aaron (Mr. DeannaCat)
Hi Caitlyn, we are planning on the sealer and caulk help our raised beds last for quite a long time, longer than if we didn’t use them at all. We think it is going to be well worth the effort. Good luck on your raised beds and let us know how the Shou Sugi Ban method works out.
Rachael
Thanks so much for this very helpful article. We just built four 4×8 boxes, with one gallon of the recommended sealer I was able to do two heavy coats of the boxes inside and out. I’d never thought about using silicone to seal the cracks, what a great idea. I finished the project today, I am confident these boxes will last for a lot longer than they would have. These tips are helping us get our money worth our of wood that is so expensive now. Thanks again.
Aaron (Mr. DeannaCat)
Hi Rachael, glad to hear you were able to build your garden beds and take the extra effort to ensure they will last as long as possible. We are anticipating our raised beds to last for quite some time and I am sure your’s will as well! Have fun filling your raised beds with soil and hopefully you will have tender seedlings growing soon!
Tara
Love this info, but I’m wondering how hard it is to keep the gravel paths and the outside edges of the beds weed free… do you have to use tons of weed killer? We’ve built the beds and the trellis supports and that all looks fantastic, but the weeds are awful. Your paths look AMAZING!!
Aaron (Mr. DeannaCat)
We laid landscape fabric across our garden area when we first started to transform the space. From there we added gravel and then the raised beds on top of that. You can see the process towards the end of this article, or you can see How to Kill or Remove Grass (& Grow Food Not Lawns!) where we take a similar approach to prevent noxious and invasive weeds from growing back. We never use weed killer or other herbicides. Hope that helps and good luck!
Tara
Thank you!! π
Michelle
Thanks for all the great info! I’d never considered caulking the cracks. Fantastic!
I’d love a little info/advice on replacing boards on existing beds and repairing them. I’ve got some termite eaten beds that need repair and am just imagining that it’s not gonna be fun.
Aaron (Mr. DeannaCat)
Hello Michelle, I guess it depends on what boards need replacing? If your 4×4’s or whatever you used for supports are in good shape, you can either pull the soil away from the side of the bed that needs replacing with a shovel until no soil is touching the bed. From there, if you used a drill to screw the boards on, just unscrew them from the corners and remove the deteriorated board and replace it with a new one. You may possibly be able to slide cardboard or thin plywood in between the soil and side of the bed if you didn’t want to remove some soil, hopefully creating a barrier between the soil and the boards you want to remove. Also, depending on your space and how many raised beds you have, it may just be easier to fully replace the raised bed with a new one. Granted you will have to remove a fair amount of soil which may or may not be possible, we have had to do this once and while it wasn’t fun, we were able to do it fairly easily. I may be able to offer more advice if I knew how the beds were constructed and what parts of the beds are in most need of repair. Hope that helps and good luck!
Lisa
The new beds look so beautiful. What do you guys recommend for on-going/future maintenance, of the exteriors? Love seeing how you guys are building out your new home π
Aaron (Mr. DeannaCat)
Hello Lisa, we will just let the outside age naturally as we enjoy the look of the beds as they age. We could have used the same sealer we used on the inside of the bed on the outside but we opted not to. Other sealers, like the tung oil linked in the article should be applied every year or so for best results which is a bit more work than we want to take on. Hope that helps and thank you for the kind words!
Lori
Thank you for so much great info on the raised garden beds, we are in the process of building our right now out of cedar. This article couldn’t have been more perfect! Thank you again.
Aaron (Mr. DeannaCat)
That’s great to hear Lori! Good luck on your raised bed building and hopefully they are ready for spring!