Is Plastic Liner Safe For Garden Beds

If you have raised garden beds, you may be wondering whether it is wise to line them, and if so, what you should use. I looked for pros and cons of lining raised beds, and I found both.

So, should you line a raised garden bed? Yes, you should line your raised garden bed, since the pros of doing so outweigh the cons. A liner for your raised garden bed can insulate the soil against extreme temperatures, keep moles and gophers out, and prevent weeds from growing. A raised bed liner will also allow water to drain away without taking soil with it.

Of course, there are some downsides to using raised bed liners, and we will discuss those as well. We'll also look into the different materials you can use for raised bed liners, along with pros and cons of each.

If your raised beds are old and rotting, check out my article on how to prevent it from happening.

Should You Line A Raised Garden Bed?

After weighing the pros and cons, I think that lining your raised garden bed is worthwhile. However, you may decide differently based on your own situation.

raised bed — There are pros and cons to lining a raised garden bed – sometimes it depends on what you are growing.

Let's review the pros and cons of lining your raised garden bed, so that you can make an informed decision on your own.

Benefits Of Lining A Raised Garden Bed

Three of the main benefits of lining your raised garden bed are:

soil insulation (avoid drastic temperature changes)
pest protection (keep gophers, moles, and other pests out)
weed prevention (stop the seeds of weeds from growing)

Some plant bed liners will also keep soil in your raised bed while allowing water to drain away. If you build your raised bed out of pressure treated wood or railroad ties, a liner can also prevent harmful chemicals from leaching into the soil.

Raised Bed Liners Insulate Soil Against Extreme Temperatures

By their nature, raised beds are sensitive to temperature fluctuations. Since the soil in a raised bed is elevated aboe ground, it will gain or lose heat faster than soil in the ground.

Using a liner in your raised bed will help to limit extreme temperature changes. This will prevent your plants from getting too cold or too hot.

wooden raised garden bed — Add a liner to a raised bed to prevent extreme temperature changes during the day or night.

A plant bed liner helps to retain heat from daytime sun in the soil. This will prevent damage to plant roots from nighttime cold or late spring frosts.

Of course, you may also want to cover your plants with a cloche or row cover to protect the stems and leaves. For more information, check out my article on protecting plants from cold and frost.

Likewise, a liner will help to prevent the soil in your elevated garden bed from heating up too fast on a hot, sunny day. This will stop the soil from drying out so quickly in the summer.

Raised Bed Liners Keep Pests Out

Raised beds are also great at keeping pests away from your garden. However, a raised bed with no bottom may not do any good against moles, gophers, or other digging creatures.

If you line the bottom and sides of your raised bed properly, moles and gophers will not be able to dig their way through it.

Even if they could somehow manage to dig through, it might not be worth the trouble. In that case, they are more likely to keep on digging for greener pastures that are an easier target.

A thin sheet of plastic is probably not enough to keep moles and gophers from digging through. You will need something a little tougher for your liner, such as hardware cloth (more detail about this later!).

Raised Bed Liners Prevent Weeds From Growing

This is especially important if you have just installed a new raised bed, or are thinking of doing so. When you build a raised bed over a spot in your yard, there may be seeds from weeds in the soil under that spot.

Those seeds may eventually sprout and grow up into your raised bed. This is much more likely if your raised bed has no bottom.

You can prevent the problem of weeds with a liner, since most weeds will not be able to grow through sturdy plastic or cloth liners.

Of course, seeds from weeds can still fall into your raised bed from wind, birds, or other animals. However, a liner does help to make it less likely that weeds will take root.

Raised Bed Liners Retain Soil While Allowing Water To Drain Away

If your raised bed has no bottom, then it is possible that watering and rain can wash away soil. Over time, this will lead to a lack of organic material and nutrients for the plants in your raised bed.

Installing the proper liner for your raised bed will allow water to drain away without taking soil with it. A liner made of cloth or other water-permeable materials will allow your raised bed to drain without losing all of its nutrients over time.

As long as an elevated garden bed is well above the surrounding ground, it will drain faster than soil at ground level.

Raised bed liners that allow proper drainage also prevent over watering. For more information, check out my article on over watering.

Raised Bed Liners Prevent Leaching Of Chemicals Into Soil

This won't be a problem if you built your raised bed from untreated wood, brick, or stone. However, you may have used pressure-treated wood, railroad ties, or wood from pallets of a questionable origin.

In that case, the wood may contain chemicals that you do not want in your vegetable garden. If the wood is in direct contact with the soil, these chemicals can leach into the soil and eventually to your plants.

wood pallets — Wood pallets may contain chemicals that you don't want in your garden soil.

To prevent this, use a liner material (such as plastic) that will prevent leaching. If you are also worried about water drainage, try using cloth or some other water-permeable material for the bottom of your raised bed, and use plastic for the sides.

This will allow drainage through the bottom while preventing soil from contacting old wood that may contain chemicals.

You can learn more about the materials available for raised garden beds in my article here.

Drawbacks Of Lining A Raised Garden Bed

For all their benefits, raised bed liners do have some drawbacks:

First of all, a completely airtight and watertight liner material may not allow the drainage that your soil needs.
Also, it can be easy to damage some liners when digging or replacing soil in your raised bed.
In addition, you will need to move all of the soil in your raised bed to replace an old liner.
Finally, if your raised bed is built from wood, a liner can keep water in contact with the wood, causing it to rot faster.

Let's start with a big concern for raised bed gardening: adequate drainage.

Raised Bed Liners May Not Allow Adequate Drainage

If you use plastic that is not water-permeable, then water will have a hard time draining out of your raised bed. This can keep the soil too moist, especially during periods of cool, wet weather.

Eventually, wet soil will lead to root rot of the plants in your raised bed. If you are worried about this problem or live in an area that gets lots of rain, make sure to use a garden liner that is water-permeable (more on this later).

Raised Bed Liners Are Easily Damaged By Digging

It is almost inevitable that you will need to dig in your raised garden bed. For example, you may need to harvest potatoes or other vegetables that grow underground.

You may also need to dig up old plants to make room for new ones in the next growing season. Either way, digging in your raised bed creates the risk of putting a hole in your liner.

There are some tough liners will resist damage from digging. However, thin plastic liners or old pool covers are pretty easy to cut with a trowel or shovel.

shovel — Be careful when digging deep or around the edges in your raised garden bed, or you may damage the liner.

To avoid making holes, make sure you know how deep the liner is buried. Dig carefully as you go deeper. Also, dig slowly near the edges of the raised bed to avoid ripping the liner.

Raised Bed Liners Are Difficult To Replace

Both age and accidental damage can wear down a liner, making a replacement necessary. This is no easy task, since you will have to:

remove all of the soil
take out the old liner
put in the new liner
replace the soil

wooden raised garden beds — Removing and replacing soil to change old liners is a lot of work when you have multiple raised garden beds!

Either way, you will need to move the entire volume of your raised bed not once, but twice, to replace your liner. This may create more work for you in some cases, but not if you plan ahead!

For example, let's say that your raised bed is made of untreated wood, and you think it will last 5 years before rotting away. In that case, choose a material for your liner so that it lasts 5 years.

That way, you can just remove the old raised bed and liner at the same time. Then, you can build a brand new raised bed and add a new liner at the same time.

Raised Bed Liners Can Cause Wood To Rot Faster

If you use untreated wood to build your raised bed, it will rot faster when exposed to water. Covering the wood with plastic on one side or both sides can trap moisture between the wood and plastic.

rotten wood — Untreated wood may rot even faster if a raised garden bed liner traps moisture.

This can cause rapid rotting of the wood, especially in hot and humid climates. You can avoid this problem entirely with raised beds made from brick or stone.

However, the up-front cost will probably be much higher. That is, unless you can score some free bricks from a friend who tore out an old chimney!

What Do You Use To Line A Raised Garden Bed?

There are a few basic options when deciding what to use to line your raised bed:

fabric – for example, landscape fabric, canvas, or burlap (sort of like a giant grow bag).
plastic – for example, a tarp, pool cover, or polypropylene bed liner.
metal – for example, hardware cloth or rabbit/chicken wire (cage).
cardboard – for example, flattened boxes (this is one material that is cheap and plentiful – but it won't last long!).

Let's take a closer look at each of these options, including some non-toxic garden bed liners.

Using Landscape Fabric As A Raised Bed Liner

Landscape fabric prevents weeds by denying them the sunlight they need to grow. It is often made from plastic or recycled materials.

You can find landscape fabric at garden supply centers or online. For example, you can find a roll of black polypropylene (plastic) landscape fabric from A.M. Leonard.

landscape fabric black mulch — Landscape fabric is often used to control weeds, but it can also be used to line a raised bed.

Landscape fabric is somewhat breathable and so will allow air, water, and nutrients to get through. If you use it to line your raised beds, it will allow the soil to drain while also preventing weeds from growing.

Landscape fabric is probably your best bet for a raised bed liner if you want to allow adequate drainage. However, it may not be strong enough to keep gophers and moles out.

For more information, check out this article on landscape fabric from Wikipedia.

Using Canvas As A Raised Bed Liner

Canvas is a durable material made from cotton, linen, or hemp. It is often used for shoes, awnings, and tents.

jute bag — Canvas is a durable, versatile material made from cotton, linen, or hemp. It can be used for grow bags or raised garden bed liners.

Canvas is also used in gardening applications, such as grow bags or raised bed liners. For example, this roll of tan-colored canvas from Tarps Plus is tough enough for a raised bed.

Canvas is a durable material, which makes it tougher and longer-lasting than most landscape fabrics. It is also somewhat water-permeable, meaning it will provide for decent drainage if you use it as a raised bed liner.

Canvas is probably your best bet for a raised garden bed liner if you want to ensure good drainage and make it more difficult for gophers and moles to chew through.

For more information, check out this article on canvas from Wikipedia.

You can also use a burlap roll as an alternative to canvas. For example, see this 40 inch by 100 foot roll of burlap from Gardener's Edge.

burlap canvas — Burlap is made from jute, flax, or hemp, and is often used for making sacks. However, it can also serve as a raised garden bed liner.

Using Plastic As A Raised Bed Liner

A plastic garden liner is a good choice if you want a waterproof garden liner for your raised bed. You can use a plastic tarp or an old pool cover as a raised bed liner.

Since these plastics are waterproof, they will not allow good drainage if used to line the bottom of your raised bed. Your best bet is to use this type of plastic to line the sides of a raised bed made of older wood.

Then, use a water-permeable material (such as canvas) to line the bottom of your raised bed. This dual liner setup has two benefits:

the canvas liner allows water to drain out the bottom of the raised bed.
the plastic liner on the sides prevents chemicals from getting into the soil from pressure-treated wood.

Another option is to order plastic garden liners made of polypropylene fabric. These liners allow better drainage than other plastic sheet materials.

Some folks worry about whether plastic garden liners are nontoxic. If you aren't sure, ask the manufacturer, or limit your use of plastic to flower bed liners (unless you will be eating the flowers).

Plastic is probably your best bet for a raised garden bed liner if the soil in your raised beds is too dry and you need to retain moisture by preventing drainage.

For more information, check out this article on polypropylene from Wikipedia.

You can check out polypropylene liners for a raised bed at Gardeners.com.

Using Hardware Cloth As A Raised Bed Liner

Hardware cloth is a mesh material made of metal, often sold in rolls at hardware stores. You can use this strong material to line the bottom of your raised bed to prevent gophers and moles from digging in from below.

For example, you can buy a 4 foot by 25 foot roll of hardware cloth from Ace Hardware.

Some hardware cloth is treated to prevent rust or tarnish. For a nontoxic garden bed liner option, consider hardware cloth made from stainless steel that is not treated with any chemicals.

A roll of hardware cloth or chicken wire can make a good water-permeable raised bed liner to keep moles and gophers out.

Used together with canvas or landscape fabric, hardware cloth can help to prevent pests from digging into your garden while also allowing water to drain away without carrying soil with it.

When hardware cloth is used above a waterproof garden liner (such as plastic), you will discourage pests from making holes in your bottom liner.

Hardware cloth is probably your best bet if you absolutely need to keep moles and gophers out of your raised bed while also allowing for adequate drainage.

For more information on mesh materials, check out this article on mesh from Wikipedia.

Using Cardboard Or Paper As A Raised Bed Liner

You can also opt to use cardboard or paper as a raised bed liner. Just know that it will decompose quickly!

One non-toxic garden bed liner option is this weed barrier paper from the Old Farmer's Almanac at SimplyGro. It is OMRI listed for organic use, prevents weeds for up to 90 days, and biodegrades to provide nutrients for your plants.

Another option is this Weed Guard Plus paper mulch from Gardener's Supply Company. It is also OMRI listed for organic use.

flat cardboard boxes — Cardboard is cheap and plentiful, but it will not last long as a raised garden bed liner.

Cardboard is probably your best bet for a raised garden bed liner if you want a cheap and biodegradable option.

For more information, check out my article on using cardboard boxes to grow plants.

Conclusion

The following table summarizes the materials you can use for a raised garden bed liner and why you might want to use each one:

Material	Benefits
Landscape fabric	-prevents weeds -semi permeable
Canvas or Burlap	-prevents weeds -semi permeable -tougher than landscape fabric
Plastic Tarp	-prevents weeds -retains water (not permeable)
Hardware Cloth	-highly permeable -tough enough to stop gophers/moles
Cardboard	-prevents weeds -semi permeable -inexpensive -biodegrades fast

This table gives a summary of some
raised garden bed liner materials
and the benefits of each.

Now you have some ideas about the pros and cons of using a raised bed liner in your garden. You also know about the different materials you can use, along with some of the pitfalls and what to look out for.

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

If you need to replace an old raised bed or start a new garden, then check out my picks for the best raised garden beds on Etsy.

You might also enjoy this article about creative raised bed ideas and alternatives!

If you are starting a garden, you can learn the basics on this page.

If you want to read some of my most popular posts, check out the "Best of GreenUpSide" page here. Enjoy!

~Jonathon