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”). 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.
Related: After reading these tips, pop over and follow our step-by-step guide on how to build raised garden beds – video included!
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Garden beds made from wood are a classic choice for creating attractive and productive garden spaces. However, exposed wood can deteriorate over time from constant moisture exposure. Protecting your wood garden beds is crucial for extending their lifespan and preserving their beauty.
In this comprehensive guide we’ll cover the key strategies for safeguarding your wood garden beds against rot, decay, insects, and more. Read on to learn wood selection, sealing techniques, protective finishes proper construction methods, and maintenance tips that will keep your garden beds thriving for years to come.
Choosing the Right Wood
The type of wood you select for building garden beds plays a major role in durability. Some woods have natural properties that make them more resistant to moisture damage and insects. Others require more protection to last over time.
Naturally Rot-Resistant Woods
Cedar, redwood, and cypress are excellent choices for garden beds. Their dense grain and natural oils make them less prone to rotting and insect infestations. Cedar and redwood, in particular, contain tannins that deter termites and other pests. These woods can potentially last over a decade without added protection.
Avoid Softer Woods
Woods like pine, fir, and spruce lack natural rot resistance. Their softer grain absorbs moisture more readily, causing faster decay. These woods require diligent sealing and frequent replacement to be used for garden beds. Even pressure-treated softwoods have a shorter lifespan than naturally durable species.
Use Wide, Thick Boards
Wider planks with thicker boards withstand moisture and pressure better than thinner pieces. For example, 2×6 boards will outlast 2x4s. Large 4×4 supports provide sturdier corner posts than 2x4s. Reduce potential points of water intrusion by minimizing seams between boards.
Sealing and Protecting Wood
Sealing wood is vital for waterproofing it against constant soil contact and moisture. Effective sealants penetrate wood pores to prevent water absorption.
Food-Safe Wood Sealants
Choose sealants without toxic chemicals since they’ll be used on garden beds. Food-safe options include:
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Tung oil – Made from natural tree nuts, penetrates wood for water resistance. Reapply annually.
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Mineral oil – Penetrates deeply to protect from moisture. Reapply every 2 years.
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Beeswax – Creates protective coating that repels water. Reapply 1-2 times per year.
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Linseed oil – Contains natural preservatives. Reapply every 2-3 years.
Seal All Surfaces
Seal all sides of wood, especially the insides of beds where wood contacts soil. Allow proper drying time between coats. Two coats provide adequate protection, while three coats ensure maximum coverage.
Seal Seams
Waterproof wood seams and gaps with flexible silicone caulk to prevent moisture collection. Carefully seal all corners, joints between boards, and end grain.
Smart Construction Strategies
Proper assembly and support components boost the longevity of wood garden beds.
Elevate Beds Off Ground
Prevent excess moisture from pooling under beds by resting them on gravel or landscape blocks. Dig a trench and fill with rocks or pebbles before setting bed frames on top.
Secure Corner Posts
Reinforce the structure with sturdy corner posts and brackets. 4×4 posts last longer than 2x4s. Metal brackets add further stability to resist bowing outward.
Promote Drainage
Never restrict drainage by lining beds with plastic sheeting. Instead, fill with loose, porous soil and add drainage holes if elevating beds. Gravel bases also encourage drainage.
Helpful Maintenance Practices
Diligent care and upkeep will maximize the lifespan of your wood garden beds.
Regular Cleaning
Keep wood free of dirt and debris that trap moisture and attract insects. Gently wash boards with mild soap and warm water when needed.
Yearly Inspections
Check for cracks, warp, mold, and other damage. Catch issues early and make repairs before problems spread. Replace any rotten boards immediately.
Monthly Sealer Reapplication
During the growing season, reinforce sealer on the inside corners and edges of beds monthly. This added protection combats constant soil moisture.
Off-Season Sealer Coats
Remove soil and apply fresh sealer to the entire inner bed surface at the end of each growing season. Touch up exterior sealer if needed.
Pest Prevention
Keep surrounding areas clear of debris and overgrowth. Apply diatomaceous earth around beds to deter crawling insects.
Check Moisture Levels
Monitor soil moisture frequently. Allow beds to dry adequately between waterings. Add mulch to maintain even moisture if drainage is poor.
With diligent wood selection, sealing, construction, and care, your garden beds can last for decades while nurturing generations of healthy plants. Give your beds the protection they deserve this season!
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.
We make our heart redwood raised beds with 4×4 corners and 2×6″ boards. These beds were extra tall, but now we usually make them 3 boards high. We haven’t been able to find 8″, 10″, or 12″ tall boards here easily – but we’d use those if we could!
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.
Applying silicone to all the board seams with a caulking gun. For reference, I needed about one 10 oz tube of silicone to seal each garden bed measuring 4 x 8’ and 3 boards tall.
The final result. All sealed and waterproof!
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.
Our raised beds are set on top of gravel, with hardware cloth in the middle to block gophers. Yet you could leave the middle of your raised bed open to the native soil below and only create a “tunnel” of gravel around the perimeter for the wood to rest on.
RAISED BED HACK STOPS WOOD DECAY ATTACKS CHEAP & EASY GARDENING
FAQ
How to protect wood for a garden bed?
Using an eco-friendly wood treatment is a great way to increase your confidence that your raised beds will last a long time. I recommend at the very least coating your lumber in linseed oil or beeswax to preserve them for the long haul.
How do you keep wood from rotting in a raised bed?
- Choose the Right Wood. Naturally Rot-Resistant Woods. …
- Proper Drainage. Elevate Your Beds. …
- Apply a Protective Coating. Sealants and Stains. …
- Regular Maintenance. Inspect for Damage. …
- Ensure Proper Ventilation. Space Between Boards. …
- Prevent Soil Contact. Use a Bottom Barrier.
How long will untreated wood last in raised garden bed?
Here’s the short answer based on the type of material used for the raised bed: WOOD RAISED BED: 5-10 years. METAL RAISED BED: 30 years. STONE RAISED BED: lifetime.
Do wooden raised beds need to be lined?
Lining the bottom of your raised garden bed with a hardware cloth or wire mesh can be beneficial for preventing pests, like gophers and moles, from digging …
How do you protect a raised bed?
I recommend at the very least coating your lumber in linseed oil or beeswax to preserve them for the long haul. Some gardeners use lining between the interior of their raised bed and soil to protect the wood. Even with the lining, you’ll get seepage of water that will penetrate that wood and linger.
Do you need a wood sealer on a garden bed?
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!
Can you use untreated wood in a raised garden bed?
If you have any doubts about using treated lumber, you can line the raised garden bed to prevent chemicals from leaching into the soil. Otherwise, you can use untreated wood with eco-friendly sealants or alternative materials.
Are garden raised beds safe?
The safest garden raised beds are made from untreated wood. Free of harmful chemical preservatives, untreated wood won’t leech toxins into your fruit and veg. However, this comes at a cost. Those wood preservatives are there to stop wood rot and bugs from eating away at raw lumber.
How do you extend the life of a wooden raised bed?
The best option to extend the life of wooden raised beds is to select thicker hardwood like cedar, redwood, and cypress. 2 inches will last a lot longer than 1 inch, and adding a plastic lining will help too. If you’re in a wet climate, then treat with beeswax, tung oil, Eco Wood Treatment, or LifeTime Wood Treatment.
Can repurposed wood be used for a raised garden bed?
Avoid using repurposed wood for a raised garden bed, especially if growing edible plants, because you do now know whether it has been treated, painted, or stained with harmful chemicals. Now that you know how to protect the wood, you can build a planter or raised garden bed and start planting!