Raised Garden Bed Rotting? (Top 5 Ways to Prevent it)


Are you annoyed that your raised garden bed is rotting away?  In this post, I have 5 ways you can prevent your raised garden bed from rotting.  Some of these methods will keep your raised bed in good shape for many years to come.

There are 5 ways to keep your raised garden bed from rotting:

  • Choose rot-resistant wood
  • Stain the wood
  • Install a liner
  • Use stone to build the bed
  • Use plastic to build the bed

Of course, you can also choose a type of wood that resists rot naturally.  However, Mother Nature will still have her way over time, and even the most rot-resistant wood will eventually decay.

Let’s take a closer look at the ways you can keep your raised garden bed from rotting.  We’ll also look at when you should use each method.

How to Keep Your Raised Garden Bed from Rotting

To keep your raised garden bed from rotting, you have two basic options.  One option is to build a new raised bed out of another material.  The other option is to take steps to make the wood last longer.

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.

brick raised beds
If you build a raised garden bed out of stone, you can stop worrying about rotting wood!

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.  For example, untreated pine may only last a few years outdoors before rotting.

Certain types of wood can hold up against rot much longer.  For example, untreated redwood can last for decades before it rots away, as long as you use heartwood and not sapwood from the tree.

Here is a list of wood you might use for a raised garden bed, from least to most rot-resistant.

  • 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, pine will rot within a few years if left untreated and exposed to soil, water, and insects.
  • Oak – oak is a hard wood and is stronger than pine.  Oak will last longer than pine when used for building a raised garden bed.
  • Cypress – cypress is a soft wood, but it still holds up fairly well against rot when it comes in contact with wet soil.  Cypress resists decay and insect damage because it contains natural oils that protect the wood.
  • 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 the wood will eventually rot.  Cedar is more costly than other types of wood.
  • 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.
redwood
If you can find heartwood from a redwood tree, then the wood will last a long time outdoors.

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).

What is the Best Wood to Use for Raised Garden Beds?

The best wood for a raised garden bed 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.  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 leeway to experiment with different locations for your raised bed.  The leftover untreated pine can be used as mulch!
  • 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.
  • 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 his 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 is older and may contain dangerous chemicals:  For example:

  • 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.
  • Wood shipping pallets – some of these pallets are pressure treated and will contain CCA or other chemicals as mentioned above.
wood pallets
Older wood pallets may be treated with CCA or other chemicals.

Newer pressure treated lumber may be safe for contact with the soil in your raised bed.  However, if you are uncertain, don’t worry.  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 get 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.

Stain or Seal the Wood

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.

wood stain
Wood stain will protect wood against damage due to water and sunlight.

Make sure the wood is dry before applying stain or sealer.  Otherwise, you are just locking in moisture within the wood, instead of keeping it out.

If you are worried about chemicals getting into your soil, there are some more natural options.  For example, Gardener’s Supply Company has a clear water proofer made from juniper.

Another option from Gardener’s Supply Company is this PolyWhey sealer, made from whey (a byproduct of making cheese).

Should You Stain or Seal Your Raised Garden Bed?

Staining or sealing your raised garden bed is a good option if you want to make the wood last longer without using a liner.

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 way to protect wood from the elements without sealing or staining it.  For example, 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.

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

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 the 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 trouble 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 colors.  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.

I hope you found this article helpful – if so, please share it with someone who will find the information useful.

jonathon.david.madore

Hi, I'm Jonathon. I’m the gardening guy (not guru!) who is encouraging everyone to spend more time in the garden. I try to help solve common gardening problems so that you can get the best harvest every year!

Recent Content