The main perk of growing plants in a raised bed is having complete control over the soil growing environment. Raised beds are great in allowing proper soil aeration, efficient drainage, and can be less stress on your back.

In addition, for many backyard gardeners, raised beds offer a simpler solution to gardening instead of fixing your native backyard soil.

There are many steps when designing and constructing a raised garden. The first and most obvious decisions are usually about the layout, box materials, and what you’d like to grow. It’s easy to choose these things because it’s normally what we see whenever we’re shopping for garden boxes or searching for layout ideas.

Although the exterior is important, it is just as important to think about what goes inside the garden beds. One element often overlooked is what to line on the bottoms of raised bed gardens.

I confess that this was something that I forgot about when I recently built some new veggie beds.

There are many options in terms of what you can line the bottom of your boxes with, from cardboard and newspaper to various types of cloth and materials. Some gardeners have nothing at all lining the bottoms.

Which material is right for your beds?

The key to choosing the right material to line the bottom of your raised garden beds depends on two main factors:

what (plants) you’re keeping in your beds; and
what you’d like to keep out of your beds.

It’s easiest to think of the bottom of the bed as a connection to the native yard/property dirt below.

Do you want nutrients and worms coming into your beds freely?

Do prefer your beds to be a completely closed system, much like a huge container?

Or, maybe you let some things in and other things out?

We’ll go over these questions in more detail, and then go over the types of liners so you can choose the best liners for your raised garden beds.

Let’s get started. 🥕

What are you growing in your raised beds?

The type of plants you grow in your raised beds may help determine whether or not you need to allow direct contact with the native soil below.

Specifically, you need to think about the roots and their average depths. If you are growing plants that will produce roots that exceed the depth of your beds, you will need to ensure that whatever you line on the bottoms will allow the roots to grow.

Not allowing the roots to reach their full mature length may inhibit the growth of your plants, and if you’re planting veggies like me, the overall production.

Let’s keep using my veggie garden as an example. I have raised beds of approximately 14 inches tall. I know that I’m going to be growing veggies exclusively in these boxes.

Here is a handy table on some common raised bed vegetable root lengths:

Vegetable	Root Length (inches)
Tomato (determinate)	10-15
Tomato (indeterminate)	18-24
Cucumber	15-18
Zucchini/Squash	15-18
Cilantro	6-10
Jalapeño	15 - 18
Pole Beans	15 - 18

So I need to make sure that whatever I line on the bottoms on my beds will allow for some root extension and growth because I only have a depth of 14 inches max!

I have a couple indeterminate tomatoes and lots of cucumbers that I hope will grow. I don’t want to stunt their growth by crowding their roots by putting something impenetrable like plastic-ey landscape fabric down.

Try to think about what you plan on growing.

For vegetables, check out Eartheasy’s great table on garden vegetable root lengths to get an idea of whether or not you need contact with the soil beneath your beds.

For depth of perennials, flowers, or trees, I suggest googling before you make up your garden bed to ensure you have the proper depth.

What do you want to keep out of your raised garden beds?

The first consideration is what you wanted to keep in your boxes, and now we’re going to talk about what you’d like to keep out. 🙅🏻‍♀️

We’ll go through some common things to keep out of your boxes, and if you’re planning on trying to keep these away from your garden boxes, keep them in mind when we go over the types of liners in a bit.

Weeds

I think it’s fair to say that we all would like to keep unwanted plants out, like weeds, and only grow our intended plants. But are you in an area with weeds that seem to grow through concrete? I know that some weeds are inevitable, especially if they’re wind dispersed, but we’re talking about the ones so robust that they will climb through your boxes. You may need to add weed blocking to your list of “keep outs”.

Animals

Next, figure out if there are any burrowing animals on your property. These are the types of critters that have the potential to invade your garden boxes from underneath, perhaps without you even knowing until it’s too late. Plants will disappear or fall over, or your tubers will be gone. Have you noticed any holes in your yard or other gardens? If so, you may be in an environment that favors burrowing animals, such as moles, gophers, ground squirrels, and voles.

Do you recognize any of these common burrowers in your area?

Ground Squirrels

Ground squirrels are about 12 in long and with about a 5 in tail.

Here are some clues that you may have them:
They like to dig into things, like pots, containers and raised beds. They are either trying to bury nuts or look for seeds/seedlings to munch on. They are also known to dig tunnels underneath the dirt.

They like to eat portions of tomatoes, apples, pears, and squash. Sometimes they just take a bite and move on.

Voles

What’s up? I look kinda like a mouse but I’m a vole!

These animals are 3-9 inches big, with a long and narrow tail.

Here are some clues that you may have them:
Voles like to eat plants themselves so you will often find them collapsed or uprooted. They are really also into tubers and bulbs, so if you are growing root veggies like potatoes, onions or beets, they may come feast on those. A telltale sign is that the top will have fallen over.

Moles

Moles vary in size from about 4 to 6 inches.

Here are some clues that you may have them:
Moles live primarily underground hunting insects. They are avid tunnel-makers and can destroy the underground growth of your plants as well as allow for other types of animals to make their way into your yard.

Gophers

Gophers are about 6-8 inches in size.

Here are some clues that you may have them:
These burrowing rodents like to feed primarily on roots and bulbs. Often the whole plant will disappear underground as the gopher sometimes like to eat the entire plant.

Toxins/Contaminants

The last issue to think about is contaminants or toxins in dirt. Are you starting a garden bed that was previously used for commercial or industrial purposes. This is more for those who are planting in urban/city gardens. Possible soil contaminants include Lead, cadmium, arsenic, zinc, and polycyclic aromatic hydrocarbons (PAHs) and may be at high levels that would be potentially dangerous for growing food.

As an aside, the soil may be highly deficient in other nutrients and may be so compacted that it would be difficult to use in any case.

In general if there’s any reason to believe that that soil contains toxins or contaminants that are unsafe, it’s best to use a closed system for container gardening.

There are ways to assess the possibility, including getting environmental assessments from the local government. All the details as well as good sources on the nature of contaminants, as it pertains to urban gardening can be found on the EPA’s website.

What am I trying to keep out of my garden beds?

For my situation, I live next to a grassy hill over the top of which I can frequently see cows from the nearby farm.

It’s an incredibly scenic and beautiful place for us. It’s an incredibly scenic and beautiful place for ground squirrels as well.

Like herds of them. I don’t even know if groups of squirrels are called herds. Ok, I googled it. It’s called a scurry or dray.

Anyways. They have decimated my cilantro in pots, chewed on my succulents, and dug a few holes in the yard.

I know they will be an issue in my new garden, so ground squirrels are the number one issue that I’m trying to address with my liners.

Types of liners for raised bed gardens

Ok, have you thought about what you’d like to keep away from your beds? Let’s go over our choices for liners. We’ll go from the most exposed/least protective to the least exposed/most protective.

Nothing

By going commando with lining the bottoms of your garden beds you are allowing for complete flow between the native dirt and the soil in your garden boxes.

This can be a great choice. Maybe your boxes are relatively shallow and will need the extra depth to grow your plants. This is great because the roots can grow as deeply as they need to.

Worms and nutrients can enter as they are needed and water can drain out as to not waterlog the boxes.

Just be sure that you don’t have any of the three issues we went over above, and you should be good.

I didn’t line my beds for a huge raised garden bed setup in a previous house. We were living in a really dry and hot climate.

There were no pests to speak of, unless you counted little lizards and the occasional garden snake. The soil was very clay-like, but it drained well enough.

Including buckets of sweet potatoes, which really loved access to the soil underneath. Nothing came to eat my potatoes so we had a huge harvest! (Probably at least 100 lbs!)

Cardboard or old newspaper

Laying down paper products is popular for the lasagne gardening method. Generally speaking, adding cardboard or newspaper to the bottom of your boxes in addition to whatever liner you end up going with is a fantastic idea.

The reason is that paper, like newspaper and cardboard, are great as your carbon-based or “brown” matter that will break down over time to provide nutrients for the microbes in your soil and aeration to your soil.

Even if you don’t place it on the bottoms of your garden bed, it’s a great weed blocker and source of carbon for the tops of your beds. It can look messy, so if you’re worried about that, just bury it beneath some mulch for a cleaner look.

As a liner, it will degrade over time and so is really just temporary. If you have one of the major issues outlined above, I suggest pairing this with something more long lasting.

Landscape Fabrics

Landscape fabrics or geotextiles, are the next step up in terms of liners. All landscape fabrics are permeable to some extent, meaning that no matter which you choose, they will still allow various amounts of water and nutrients to pass through.

There are two categories of landscape fabrics: non-woven or woven.

Non-woven landscape fabric is typically made of synthetic materials such as polypropelene or polyester. It’s bonded together using heat instead of weaving methods, and can often feel like felt. These fabrics are less durable that their woven counterparts, but offer much better drainage.

I’m still doing landscaping in my front yard and it feels kinda of felt-y if that makes sense. This is what non-woven fabric looks like:

On the other hand, woven landscape fabrics are made of polypropelene or linen. Threads from various materials are woven together, and this type of fabric looks like it has a woven pattern on it. Generally, these have a low porosity and are not great for projects that require drainage. However, they are highly durable and will last many years. This type of fabric is often used in construction projects, such as building roads.

This is what woven cloth looks like:

The primary reason for choosing landscape fabric is for weed control. It is a non-chemical way to prevent weed growth.

Some downsides is that it may be temporary and it may be recommended to be replaced every few years depending on what type you choose. May not allow roots to grow beneath the box. Rodents should be able to chew through it quite easily. Woven landscape fabrics may not provide proper drainage, but I imagine if you were really trying to combat weeds, you could punch very small holes to ensure that your box doesn’t get water-logged.

Although not recommended for permanent landscape projects, landscape fabrics are worth considering lining your tops with landscape fabric as it is a chemical-free method to prevent weeds. It will also warm your beds a bit. You can cover with mulch for appearance and extra warmth.

Wire Mesh/Hardware cloth

These types of liners are various types of woven wire that have holes or spaces of varying sizes. They vary in strength based on the gauge that you purchase. (A good rule of thumb with wire gauges: The smaller the number, the thicker the wire.)

Chicken Wire/Poultry Mesh

Typically made of galvanized steel (coated with zinc as to prevent rusting), this type of wire has hexagon shaped holes that range in diameters from roughly ½ an inch to 1 ½ inches or larger. They vary in gauge, so give it a feel before purchasing to see if it fits your needs.

This type of wire is typically used to keep farm chickens and the like confined to a certain area. It can also be used as a lightweight liner for garden beds. It is relatively inexpensive.

Hardware cloth

Hardware cloth is wire mesh with square openings that vary in size from 1 inch to as small as ¼ inch. It also varies in gauge, with some that are very stiff and difficult to bend. As a liner for a garden bed, it is very sturdy and highly protective of all types of digging rodents.

Depending on the size of your burrowing animals you’ll want to pick a liner that has holes that are small enough that they can’t get through, but big enough to let roots go down if they need to and earthworms come up if you want to.

For full protection, make sure to fasten the hardware cloth to your beds using nails or staples so rodents can sneak through the edges and corners.

The one downside is that it can get very pricey if you plan on lining lots of beds.

So which liner will you choose? Maybe it will be a combination of a couple choices?

So what did I lining my latest raised beds with?

Our boxes before we leveled the ground and built them up!

I bought some thick chicken wire as it seemed to be the best bang for the buck.

I debated on using hardware cloth with smaller holes, but I really haven’t had an issue with smaller digging rodents.

The ground squirrels around my house are really quite large and the chicken wire I purchased had rather small holes. Given they weren’t as small as the hardware cloth holes, but I really couldn’t justify the price tag for a problem I didn’t yet have.

In addition, the gauge was low enough where I felt it was sturdy to stand the test of time. At least until I need to dig up the boxes again.

I stapled it to the inside of my boxes and hopefully I’ve kept the squirrels from digging underneath my boxes.

Climbing on top of my boxes….well, that’s another story.

There is no right or wrong way with gardening, just do the research, make a choice, and move on. It’s all about experimenting, so try and see what happens.

Hi! I’m Adriana.

Apr 30 Should you line the bottom of your raised garden bed?

Which material is right for your beds?

The key to choosing the right material to line the bottom of your raised garden beds depends on two main factors:

what (plants) you’re keeping in your beds; and

what you’d like to keep out of your beds.

What are you growing in your raised beds?

Here is a handy table on some common raised bed vegetable root lengths: