It’s easy to get annoyed when your raised garden bed starts to rot away, especially if you spent a lot of time and money to put it together. Luckily, there are ways to prevent raised bed rot and get more life out of your raised beds.
Here are 5 ways to keep your raised garden bed from rotting:
- Choose rot resistant wood (build a raised bed with wood that does not rot)
- Stain the wood
- Install a liner
- Use stone to build the bed
- Use plastic to build the bed
You can choose a naturally rot resistant wood (such as cedar). However, Mother Nature will still have her way over time, and even the most rot-resistant wood will eventually decay.
In this article, we’ll take a closer look at each of the 5 methods to keep your raised garden bed from rotting. We’ll also look at when you should use each of methods.
Hopefully, we can keep your raised bed in good shape for many years to come.
Let’s begin.
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How To Keep Your Raised Garden Bed From Rotting
To keep your raised garden bed from rotting, you have two basic options:
- 1. Build a new raised bed out of another material (Ideally, a material that does not rot).
- 2. Take steps to make the wood last longer (for example, use stain or liner).
If you build a raised bed out of stone or plastic, it will last much longer than one made out of wood. You also won’t need to bother with treating wood to protect it from the elements.
However, wood is much lighter than stone, and wood looks more natural in your garden than plastic. You can protect wood by installing a liner or by using a stain or sealer to treat it.
You can make a raised garden bed last much longer if you choose the right type of wood before treating it. Even if you don’t treat the wood, certain types will resist rot and decay for many years.
How Long Will Untreated Wood Last In Raised Beds?
Untreated wood may rot in as little as 3 years when exposed to water, soil, and insects. However, not all wood is created equal when it comes to raised beds.
Image courtesy of user:
SFW Construction via:
Wikimedia Commons. https://commons.wikimedia.org/wiki/File:Deck_beam_dry_rot.jpg
For example, pine is good for building, but untreated pine may only last a few years outdoors before rotting. According to the University of Georgia Extension, pine has no way to resist rot and insects, especially if in contact with wet soil.
One exception would be older pine (40 years or older). You might be able to find some of this sturdy pine by reclaiming wood from an old barn.
Certain types of wood will resist rot and last much longer than pine. For example, untreated redwood can last for decades before it rots away.
This assumes that you use heartwood and not sapwood from the tree. According to the University of Nebraska-Lincoln, heartwood is found inside the tree, not in the outer rings.
Heartwood is actually older sapwood that has died and become harder. New sapwood is lighter and helps to move water throughout the tree’s stem and branches.
Here is a list of rot resistant wood types you might use for a raised garden bed (from least to most rot-resistant):
- Pine
- Oak
- Cypress
- Cedar
- Redwood
Let’s take a look at each of these wood types in more detail.
Pine
Pine is a soft wood that is often used for building furniture. Pine does not resist the elements well, so it is less useful for outdoor projects.
In most cases, untreated pine will rot within a few years of exposure to wet soil and insects. It might be a good choice if you want to change the location of your raised beds often.
Oak
Oak is a hard wood and is stronger than pine. Oak will last a little longer than pine when used for building a raised garden bed.
There are 2 downsides to using pine for a raised garden bed:
- Oak is expensive compared to pine.
- Dry oak is difficult to work with.
Cypress
Cypress is a soft wood like pine. However, it holds up against rot better than pine when it comes in contact with wet soil.
Cypress resists decay and insect damage because it contains natural oils that protect the wood. Cypress is native to the southeastern U.S., so you might find it more affordable if you live in that region.
Cedar
Cedar is another soft wood, but it holds up well outdoors. Like cypress, cedar contains natural oils that protect it against rot and insects.
Keep in mind that the red appearance of cedar will naturally fade to gray and rot over time.
There are a few drawbacks to using cedar for a raised garden bed:
- It is more expensive than other types of wood.
- It is dense, making it hard to work with.
- It is prone to splitting from screws, unless you pre-drill the holes.
You can find some quality cedar raised garden beds from Etsy on this page.
Redwood
Redwood is a soft wood, and it is one of the longest lasting types. Even when exposed to wet soil and insects, redwood is a champion at resisting rot.
Redwood is expensive, but it can last up to 30 years. If you want your raised beds to last for a long time, the cost might be worth it.
Remember that for any of the longer-lasting types of wood, you want heartwood, not sapwood, in order to get lumber that will really last. It may be a tall order to find heartwood, and it can be very expensive if you do find it.
You can learn more in this article about wood myths from the University of Massachusetts at Amherst.
You can make your wood raised garden bed last even longer if you treat the wood with stain or paint. You can also use a raised garden bed liner to protect the wood (more on this later).
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What Is The Best Wood To Use For Raised Garden Beds?
The best wood for raised beds depends on your preferences.
Do you want to save money, or spend more to go natural and still have a long-lasting raised bed?
- For a quick, cheap, chemical-free, short-term option: use untreated pine to build your raised garden bed. Sure, it won’t last long when untreated. However, you can build a new raised garden bed in a few years, and possibly in a different location. This gives you freedom to experiment with different locations for your raised bed. The leftover untreated pine can be used as mulch or turned into compost!
- For a durable, cost-effective option: use oak to build your raised garden bed. Then, finish it with a natural wood stain or sealer. If you are worried about chemicals from the stain or paint leaching into your soil, use a raised garden bed liner to separate the wood from the soil (or choose a non toxic wood sealer – more on this later).
- For a natural, chemical-free, long-lasting option: use untreated cedar or redwood (heartwood, not sapwood) to build your raised garden bed. Both of these woods contain natural oils that protect them against rot and insects for a long time. Just keep in mind that this option will be expensive.
Can You Use Treated Lumber For Raised Garden Beds?
You should avoid using treated lumber for raised garden beds. This includes any “recovered” wood that may contain dangerous chemicals, such as:
- Railroad ties – these are treated with creosote, which will leach nasty chemicals into the soil.
- Pressure treated lumber – some of this lumber is treated with CCA (chromated copper arsenate), which is another nasty chemical that you don’t want in your garden.
- Wooden shipping pallets – some of these pallets are pressure treated and will contain CCA or other chemicals as mentioned above. So, be careful and know your source before you use recovered pallets to make a wooden raised bed.
Newer pressure treated lumber may be safe for contact with the soil in your raised bed.
However, don’t worry too much if you are uncertain about the age or source of the wood. You can use a raised garden bed liner to separate the soil from the wood.
Another alternative is to use a longer-lasting untreated wood, as mentioned earlier.
4 More Ways To Keep Your Raised Garden Bed From Rotting
It’s time to dig into some methods you can use to keep your raised garden bed from rotting.
The first 2 methods are useful if you have already built a raised garden bed out of wood.
The last 2 methods are possible alternatives to wood if you have not built your raised garden bed yet (or if you need a replacement bed).
Stain Or Seal The Wood
They might seem like the same thing, but stain and seal are a little bit different.
The purpose of wood stain is to change the color of wood and protect it against damage from water and sunlight.
On the other hand, the purpose of wood sealer is simply to protect the wood, without really changing the color.
How To Seal Wood For Raised Garden Beds
To seal wood for raised garden beds, take these steps:
- First, make sure the wood is clean and dry – otherwise, you are just locking in moisture with the stain or sealer. If the wood is freshly cut, it may not be dry enough. It could also be wet if it sat out in the rain. Put the wood in a dry, covered spot (garage, etc.) and use a space heater if necessary to speed up the process.
- Next, make sure that you have a fresh, clean brush to use when you apply the sealer. It wouldn’t make much sense to buy non toxic stain or sealer and then use an old brush covered with unsafe chemicals (from old paint, etc.)
- Then, choose a stain or sealer (there is a list of non toxic sealers below).
- Now, put the wood on a sawhorse or a raised surface to make it easier to apply the stain or sealer.
- Finally, use the brush to cover one face of the wood and its adjacent sides with stain or sealer. Give it time to dry, then flip the wood over and cover the other side.
If you are worried about chemicals getting into your soil, don’t worry – there are some natural options available.
Here are just a few types of non toxic wood sealer for garden beds:
- Gardener’s Supply Company carries cedar garden bed oil, which is made from a natural blend of vegetable and citrus oils. It is made specifically to protect cedar, and it is safe for contact with food.
- Gardener’s Supply Company also has a clear water proofer made from juniper.
- Green Building Supply carries this water proofer from Vermont Natural Coatings, which also uses Juniper and is non-toxic with zero VOC (volatile organic compounds).
- Another option from Ace Hardware is PolyWhey sealer made by Vermont Natural Coatings, which is made from whey (a byproduct of making cheese).
- This wood stain from ECOS Paints is non-toxic with zero VOCs.
Some of these stains should only be applied after the wood has dried out. Be sure to check the label for instructions to get the best results.
Should You Stain Or Seal Your Raised Garden Bed?
Staining raised garden beds is a good option if you want to make the wood last longer without using a liner.
The only reason to use stain instead of sealer is to change the color of the wood. For example, you could use a stain to give pine or oak a color that is more like that of cedar or redwood.
If you don’t want to use a stain or sealer, you can still use a liner to protect a raised garden made of wood.
Raised garden bed liners have many advantages, but a waterproof plastic one can prevent soil drainage. The resulting wet soil can cause root rot and other problems for your plants.
Install A Liner
A raised garden bed liner is a good way to protect wood from the elements without sealing or staining it. A plastic raised garden bed liner will keep rain and wet soil separate from the wood.
Just keep in mind that plastic can also trap moisture from the air if you live in a humid climate. Of course, any type of wood will rot and decay faster in a humid environment, whether you use a liner or not.
Do You Need A Raised Garden Bed Liner?
You do not need a raised garden bed liner to grow plants successfully. However, a liner for your raised garden bed has many benefits:
- Insulates soil – A liner helps to prevent extreme temperature fluctuations on cold nights in the spring or fall. This may keep your cold-sensitive plants (such as tomatoes or peppers) alive during unseasonably cold weather.
- Keep pests out – A liner can help to discourage pests from getting into your raised garden bed. For example, moles and gophers may give up and move on to greener pastures if they encounter resistance from a liner while digging.
- Prevent weeds – a liner can make it more difficult for weeds to grow up from the soil below your raised bed. This is especially true if the soil in your raised bed is shallow.
You can learn more about the pros and cons of raised garden bed liners in my article here.
Build From Stone (Or Brick)
If you have not built your raised garden bed yet, then you have the option of building from stone. Stone is much heavier than wood, and it will be more work to build a raised garden bed out of stone.
However, once constructed, a stone raised garden bed can last for decades upon decades. You won’t need to stain it or seal it, and you won’t need to worry about protecting it from water, soil, or insects.
Stone will hold up well, even in a climate with high humidity and lots of strong sunlight. The only problem with a stone raised bed is that it will never rot.
If you ever want to get rid of it, you will need to move it piece by piece. You can learn more about stone and other materials for raised garden beds in my article here.
Build From Plastic
Finally, you can choose to build your raised garden bed from plastic. Plastic is light, compared to both stone and wood.
It also resists rot, and comes in many different colors (you can paint some types of plastic as well). Plastic is widely available and easy to work with.
The only downside to plastic is that some types may wear down and crack over time due to sun exposure. Thin plastic may not hold up well against the weight of lots of wet soil in a tall raised garden bed.
Conclusion
Now you know how to keep your raised garden bed from rotting. Whether preserving an established raised garden bed or building new one, these methods should help to keep you gardening for a while.
If you need to figure out the volume of your raised bed, try our soil volume calculator here!
You might also want to read my article on how to cover a raised garden bed or this article on creative raised garden bed ideas and alternatives.
I hope you found this article helpful – if so, please share it with someone who will find the information useful.
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If you want to read some of my most popular posts, check out the “Best of GreenUpSide” page here. Enjoy!
~Jonathon