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 it’s easier to block out pests. I love raised beds! Yet one of the few drawbacks is that they don’t last forever (and, they aren’t 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.
I’ll admit, we never sealed our garden beds in the past. They’re made from super durable heart redwood, after all! However, once we moved to our new homestead and began building our “forever garden” (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 Birdie’s galvanized metal raised bed kits instead. Those things should last forever! (Save 5% with code “deannacat3” – plus buy 3 get 1 free currently for their 2023 Memorial Day sale). 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. I’ve also heard stories of friends’ 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. Don’t 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 2×6” boards will last longer than one made from 2×4”s. 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 ¾” 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 4×4” corner supports will last far longer than using 2×4’s 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 don’t want to use just any wood sealer on your garden beds! Many sealants and stains contain toxic chemicals – stuff you don’t 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.
Hope’s Natural Tung oil is another nontoxic option to seal garden beds, though I’ve heard it’s 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 “wood-to-earth” 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 isn’t to say you can’t have the bottom center area of your beds open to the native soil below if you prefer! I’m 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 ¾” 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. We’ve never done this ourselves, but I’ve heard one drawback is that it does take a lot of fuel and effort. Experts also say it’s 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 don’t 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 “aeration” component. Aeration additives include perlite, pumice, sand, peat moss, coco coir, rice hulls, or our favorite: ⅜” 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 “permeable” 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 ½” to ¾” 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
Great informative article! Do you seal the wood before caulking? Or could you caulk before sealing?
Aaron (Mr. DeannaCat)
Hi Tim, we sealed the beds before we caulked so the sealer could seep into the cracks and crevices, even where there was going to eventually be caulk. You could likely caulk before sealing without issue if that is what your schedule demands. Hope that helps and good luck!
I love your website and all of the awesome info! I just finished building garden boxes, prepping the new garden area by excavating a few inches below grade, gopher wire, heavy duty weed cloth and now getting ready to put 2″ to 3″ of gravel on top before setting the garden boxes on top of the gravel. My wife is concerned that setting the garden beds directly on top of the gravel or baserock will result in a lot of the soil washing out into the gravel below over time, especially during periods of heavy rain like we experienced in Santa Cruz, Ca over this last winter. Do you see much soil leaching into the gravel below and around your beds? What type of gravel do you use? Much thanks for the feedback!
Aaron (Mr. DeannaCat)
Hi Tom, we are so grateful that you enjoy the website and find the information helpful! As far as soil leaching out the bottom of the beds, we attach the hardware cloth directly to the bottom of the raised beds and don’t have an issue with soil leaching out of the bottom of the beds. If you don’t have the hardware cloth attached to the beds, even working the raised beds into the gravel an inch or two will greatly reduce the chances of soil coming out the bottom of the raised beds. As far as the gravel we used on our property, we used a 50/50 mix of 3/8th inch green rock and 3/8th inch gold granite, we like gravel that has some edges to it so it can more or less lock in place compared to a rounder rock like pea gravel. Hope that helps and good luck on your garden space!
I thoroughly enjoyed reading your blog post on how to make garden beds last longer. Your tips and insights are incredibly helpful for anyone looking to maximize the longevity of their garden beds and create a sustainable and thriving garden space.
I particularly appreciate the emphasis you placed on proper soil preparation and maintenance. Your suggestion to use organic matter and compost to enrich the soil is spot on. It not only improves the soil structure but also enhances nutrient availability for plants, promoting healthy growth and reducing the need for synthetic fertilizers.
The idea of using natural mulch to suppress weeds, retain moisture, and regulate soil temperature is fantastic. Not only does it add an aesthetic appeal to the garden beds, but it also serves as a protective barrier, preventing soil erosion and minimizing the impact of extreme weather conditions.
Your tips on proper watering techniques, such as watering deeply and infrequently, are essential for promoting deep root growth and water efficiency. By avoiding frequent shallow watering, gardeners can train plants to develop stronger and more resilient root systems.
I also appreciate the emphasis you placed on crop rotation and companion planting to prevent pests and diseases. These practices help maintain a healthy and balanced ecosystem within the garden, reducing the reliance on chemical pesticides and fostering a more sustainable approach to gardening.
Lastly, your suggestions for regular maintenance, such as pruning, weeding, and monitoring for signs of nutrient deficiencies or pest infestations, are crucial for ensuring the long-term health and productivity of garden beds.
Thank you for sharing such valuable information and practical tips. Your blog post is a great resource for both beginner and experienced gardeners who are looking to extend the lifespan of their garden beds and create a thriving garden ecosystem. Keep up the fantastic work!
Hi there, your site is awesome. Thanks for all of the information. I used the silicone on the planter box to seal the cracks but began wondering if this was the smartest decision. Should we be worried about any leaching of the silicone into our vegetables? Curious what your feedback is and if you’ve researched this as well. Thanks, Nick
Aaron (Mr. DeannaCat)
Hi Nick, we are glad to hear you enjoy the site so much and we appreciate your support! There isn’t an issue with the silicone leaching into the soil as it is chemically inert once it solidifies or hardens. Hope that helps and have fun growing!
I see that self-watering reservoirs are becoming popular. My understanding is that they need to be 17 inches from the top of the planter. If I build a planter that is 24 or 32 inches tall, do you think it would be possible to add some type of wood frame to the inside of the planter box that would hold up the water reservoir? What happens next year when I have to replace and add new soil? Thank you for your thoughts–they are much appreciated!
Aaron (Mr. DeannaCat)
Hi Anne, we aren’t entirely familiar with self-watering reservoirs or sub irrigated planters, we have used Earthboxes before but they are much smaller in size than the sized planter you intend on building as they are only 11 inches tall including the reservoir and soil space. If you need to replace the soil each season, you would either need to dig most of it out with a shovel or try and tip the planter over onto a tarp to get the soil out that way. I would try and build healthy soil so that I wouldn’t need to replace the soil each season, but again, I am not familiar with the recommendations on this step/process. Again, we are not familiar enough with these types of planters to offer too much advice, sorry and good luck with your project!
What are the dimensions of these beds?
Aaron (Mr. DeannaCat)
Hi Sarah, they are 8 feet long and just under 4 feet wide.
Thanks for the great article! Two questions. For raised flower/shrub beds, can pressure-treated lumber be used (and then sealing and the rest of the steps you mention)? And then is it okay to paint the exterior of the planter with the appropriate exterior and weatherproof paint?
Aaron (Mr. DeannaCat)
Hi Jean, we are overly cautious about using pressure treated wood but you can definitely use it in your instance. You can likely caulk the seems and then paint the lumber using the weatherproof paint, sealing the wood likely isn’t needed if you are going to paint it anyways. Hope that helps and good luck on your project!
Could we see an updated photo of how this is looking? How are the beds holding up?
Aaron (Mr. DeannaCat)
Hi Ashley, the raised beds are holding up great, the wood has turned into a more weathered gray as is typical of redwood outdoors that hasn’t been stained or sealed with a lacquer type finish, yet structurally, the beds are in the same condition as they were when we first built them. We may add an updated photo in time but you can always see garden updates and projects we are working on in real time if you follow along on Instagram. Thanks for asking and have a good day!
How long should you wait to add soil and plants to raised beds after using Garden-Seal?
Aaron (Mr. DeannaCat)
Hi Adale, it seemed to dry within a couple hours for us in between coats, adding soil the next day seems more than reasonable. Good luck!
Wow!! What a great post! Thanks for all this info. We are getting ready to build some raised beds out of cedar and we want them to last as long as possible!
Aaron (Mr. DeannaCat)
Hi Emily, thanks for reading and good luck with your raised garden bed construction!
Lots of great ideas, ever think about using pond liner for the inside of the beds to keep the soil from contacting the wood?Wrap it down the inside , under the bottom and over the top of the bottom most board. Use a 6″board as the bottom most board to hide the rubber under the gravel, 2″ thick all wood, I like the sitting on gravel idea.
Aaron (Mr. DeannaCat)
Hi Tee Jay, using a pond liner could be an idea but I would still be worried about water intrusion in between the liner and the wood raised bed, I would also be cautious of what chemicals are in the pond liner specifically as to avoid harmful chemicals leaching into the soil. We hope to get at least 20 years of use out our raised beds that were made out of redwood with the Garden-Seal sealer, but that time could vary depending on how extreme the weather is where you live. Hope that helps and good luck!