How to Build a Raised Garden Bed

Planning, Building, and Planting a Raised Garden Bed

December 21, 2018
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Learn how to easily build your own raised garden bed!

Crestock

Raised garden beds are fairly easy to construct, even easier to maintain, and offer myriad benefits for your garden (and you)! Here’s how to build a raised garden bed in your backyard, as well as some advice on using the right wood and soil.

Raised beds are an easy way to get into gardening! Whether you purchase a kit or build your own, there are many great reasons for using raised bed gardening.

What is a Raised Garden Bed?

A raised garden bed (or simply “raised bed”) is a large planting container that sits aboveground and is filled with soil and plants. It is a box with no bottom or top—a frame, really—that is placed in a sunny spot and filled with good-quality soil—to become a source of pride and pleasure, and a centerpiece of the garden.

Why Should I Build a Raised Garden Bed?

Raised beds have many benefits. Here are a few reasons why you should consider using one:

  • Garden chores are made easier and more comfortable thanks to less bending and kneeling. Save your knees and back from the strain and pain of tending the garden!
  • Productivity of plants is improved due to better drainage and deeper rooting.
  • Raised beds are ideal for small spaces where a conventional row garden might be too wild and unwieldy. Raised beds help to keep things organized and in check.
  • Planting in a raised bed gives you full control over soil quality and content, which is especially important in areas where the existing soil is rocky, nutrient-poor, or riddled with weeds.
  • Raised beds allow for a longer growing season, since you can work the soil more quickly in the spring in frost-hardened regions, or convert the bed into a cold frame in the fall.
  • Fewer weeds are seen in raised beds thanks to the bed being elevated away from surrounding weeds and being filled with disease- and weed-free soil.
  • Raised beds allow for easier square-foot gardening and companion planting.

Learn more about the benefits of raised garden beds

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Choosing the Right Wood for Raised Beds

Many people are concerned about the safety of their wood frame. First, rest assured that CCA pressure-treated wood is banned, as it was known to leach arsenic. To ensure that the wood lasts, there are several options:

  • Regular pressure-treated lumber sold today has a mixture of chemicals applied to prevent the moist soil and weather from rotting it. Although pressure-treated wood is certified as safe for organic growing, some people have reservations about using it, and there are various eco-friendly alternatives. 
  • More expensive woods, such as cedar, contain natural oils which prevent rotting and make them much more durable. They are more expensive to buy, but they will last many more years.
  • Choosing thicker boards can make the wood last longer. For example, 2-inch-thick locally sourced larch should last 10 years, even without treatment.
  • Avoid using railroad ties, as they may be treated with creosote, which is toxic.

Alternatives to wood include concrete blocks or bricks. However, keep in mind that concrete will increase the soil pH over time, and you will have to amend the soil accordingly to grow your best garden.

How Big Should Your Raised Bed Be?

  • First, you need a location that has level ground and gets the right amount of sunlight (6 to 8 hours per day). This should narrow down your options a bit.
  • In terms of bed size, 4 feet is a common width. Lumber is often cut in 4-foot increments, and you also want to be able to access the garden without stepping into the bed. Making the bed too wide will make it difficult to reach the middle, which makes weeding and harvesting a pain.
  • Length isn’t as important. Typical plots are often 4 feet wide by 8 feet long or 4 feet wide by 12 feet long. Make your bed as long as you like or build multiple raised beds for different crops.
  • The depth of the bed can vary, but 6 inches of soil should be the minimum. Most garden plants need at least 6 to 12 inches for their roots, so 12 inches is ideal.

Preparing the Site for a Raised Bed

  • Before you establish the bed, break up and loosen the soil underneath with a garden fork so that it’s not compacted. Go about 6 to 8 inches deep. For improved rooting, some gardeners like to remove the top layer (about a spade’s depth), dig down another layer, and then return the top layer and mix the soil layers together.
  • If you’re planning to put your raised bed in a space currently occupied by a lawn, lay down a sheet of cardboard, a tarp, or a piece of landscaping fabric to kill off the grass first. After about six weeks (or less, depending on the weather), the grass should be dead and will be much easier to remove.

Building a Raised Garden Bed

  • To support timber beds, place wooden stakes at every corner (and every few feet for longer beds). Place on the inside of the bed so that the stakes are less visible.
  • Drive the stakes about 60% (2 feet) into the ground and leave the rest of the stakes exposed aboveground.
  • Ensure that the stakes are level so that they’re in the ground at the same height, or you’ll have uneven beds.
  • Set the lowest boards a couple inches below ground level. Check that they are level.
  • Use galvanized nails (or screws) to fix the boards to the stakes.
  • Add any additional rows of boards, fixing them to the stakes, too.

Check out our video on how to build raised beds for your vegetables:

Soil for Raised Garden Beds

The soil blend that you put into your raised bed is its most important ingredient. More gardens fail or falter due to poor soil than almost anything else. 

  • Fill the beds with a mix of topsoil, compost, and other organic material, such as manure, to give your plants a nutrient-rich environment (see recipes below). Learn more about soil amendments and preparing soil for planting.
  • Note that the soil in a raised bed will dry out more quickly. During the spring and fall, this is fine, but during the summer, add straw, mulch, or hay on top of the soil to help it retain moisture.
  • Frequent watering will be critical with raised beds, especially in the early stages of plant growth. Otherwise, raised beds need little maintenance.

Raised Bed Soil Recipe

For a 4x8-foot raised bed:

  • 4 bags (2 cubic feet each) topsoil (Note: Avoid using topsoil from your yard, as it may contain weeds and pests.)
  • 2 pails (3 cubic feet each) peat moss
  • 2 bags (2–3 cubic feet each) compost or composted cow manure
  • 2-inch layer of shredded leaves or grass clippings (grass clippings should be herbicide- and fertilizer-free)

Makes enough for a depth of about 9 inches.

Raised garden bed. Photo by Oregon State University/Wikimedia Commons.
Square-foot gardening in a raised bed. Photo by Oregon State University/Wikimedia Commons.

Planning a Raised Bed Garden

To plan out the perfect garden for your space, try the Almanac Garden Planner! In minutes, you can create a garden plan right on your computer.

The Garden Planner has a “Raised Garden Bed” feature. It also has a specific square-foot gardening (SFG) feature, which involves dividing the bed into squares to make the organization of your garden a lot simpler (see photo above).

Which ever garden you select, the Garden Planner will show you the number of crops that fit in each space so you don’t waste seed or overcrowd. There’s even a companion planting tool so you plant crops that thrive together and avoid plants that inhibit each other.

Test out our Garden Planner with a free 7-day trial—plenty of time to plan your first garden! If you enjoy the Garden Planner, we hope you’ll subscribe. Otherwise, this is ample time to play around and give it a go!

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Learn More

Have you ever thought about building your own raised garden bed? Or do you have one already? Tell us about it below!

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Reader Comments

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If your beds are 12” deep

If your beds are 12” deep then this should be enough to kill off the grass below, but if you have perennial weeds among the grass or very invasive grass species, you might prefer to put down mulch fabric or newspaper several sheets thick as a barrier below your bed.

If your peas and beans are

If your peas and beans are climbing varieties you might like to grow them on the North side of your bed to avoid shading your other crops. Tomatoes are also tall, while melons and pumpkins will sprawl across the ground (unless you train them up a trellis or similar). Our Garden Planner automatically spaces plants to make it easy to see how many plants you have room for. You can find out more and take out a free trial at http://gardenplanner.almanac.com

If I were to do a 12 inch

If I were to do a 12 inch raised garden over a spot that was previously a garden , should I place landscape fabric under the raised garden between the ground and raised garden? Or should I just double dig the ground and place new compost soil over it?

There’s no need to place

There’s no need to place landscape fabric underneath the raised bed, unless you have a problem with perennial weeds which might make their way into the raised bed. 12 inches of soil will be enough for most vegetables, so you don’t need to dig the ground beneath either.

I am thinking of building a

I am thinking of building a raised veg garden. Because of back issues I am thinking I would like to build one 3 ft high at lease. I am also on a limited budget. As I will only need 12" or so of soil for the vegies, what could I use to fill in the bottom 2 feet that won't cost a fortune?

Some people fill the bottom

Some people fill the bottom of taller raised beds with rubble as this is often available free or cheaply. 

What can you fill the bottom of a taller raised bed

What would be advised that would not impact the “organic” status of our garden?

Raised garden, plastic lining

Raised garden, plastic lining or not??

would it effect my ground

would it effect my ground water in any way to have a raised bed garden right near and around my well? It would be an organic garden, but wondering if this should be avoided altogether Thanks

I want to use cinder blocks

I want to use cinder blocks to make some raised beds. We have 150 of them hanging around. I understand there is ash that comes from coal in the cinder blocks, so they are not advised for food crops. Actually some articles say it will leech, some say it would take chemicals to make it leech. I keep reading you can line the beds with plastic. Can you all tell me what type of plastic you are using? Is it something special?

When lining raised beds, most

When lining raised beds, most people will use an impermeable plastic sheet that is thick enough to last a long time. If you’re unsure of its suitability for food crops, read the label or contact the manufacturer for advice.

You might consider using weed

You might consider using weed barrier cloth. It doesn't break down so much and won't allow a pool of water lying in the bottom

I am placing a raised bed on

I am placing a raised bed on an old rock garden. It has a couple inches of pea rock. Should I move all the rock out or just fill with new soil on top? Is it good for drainage or better to move the rock?
thanks

You can build the raised bed

You can build the raised bed on top of the rocks. They will provide good drainage and keep weeds at bay.

Hello. My husband made me 2

Hello. My husband made me 2 raised garden beds next to the house. Last year we tried our first garden. He had treated the inside so it wouldn't rot. He put down rock first, then mulch & then soil. The plants were really dry looking even though I watered. Tomato plant only produced a tiny tomato. Strawberry plant produced 1 or 2 strawberries. Zucchini didn't produce. Oh....& we ended up with these great big mushrooms along the roots & around edges of the bed. Dumping everything in beds & starting over this spring. Could you help me out on what we messed up on please? & should I use plastic being would was treated & stained?

what kind of soil? it's all

what kind of soil?

it's all about the soil!

Make your Beds out of 2'x 6'x

Make your Beds out of 2'x 6'x 8' Red Cedar and they will last 10 years or more.

Garden Soil
Mushroom Soil (Compost)
Compost
Perlite
Vermiculite

Call your local Landscape company they can deliver up to 6 yards. This will fill 3 Beds 4' wide x 8' long x 1' deep They will mix it for you also.
Get half Garden Soil half Compost and a big bag of perlite or vermiculite to mix in the Garden Beds as you fill. Mix in quite a bit you want nice and light Soil.

Perlite - a form of obsidian characterized by spherlulites formed by cracking of the volcanic glass during cooling, used as insulation or in plant growth media.

My first concern is, what did

The Editors's picture

My first concern is, what did your husband treat the inside of the beds with? You need to make sure that it’s an eco-friendly wood treatment since you’re growing food in that soil. If it wasn’t, instead of starting from scratch again, lining the inside of the bed with plastic will help prevent any chemicals leaching into the soil.
Raised beds do tend to dry out quickly so need plenty of irrigation, and if your growing medium is mostly garden soil then this will dry out much faster than if it was mixed with plenty of compost (or you could use bagged potting soil). Soil on its own is also unlikely to be rich enough for good fruit production. I wouldn’t worry too much about the mushrooms though - their presence is often a sign of healthy soil. 

I will be trying my hand at a

I will be trying my hand at a raised garden this spring. I want to plant cucumbers, tomatoes, okra, yellow squash, bell pepper and maybe some romaine lettuce. What size bed should I be thinking about? I don't can, and I don't have a large family to feed.

We're happy to help. You

The Editors's picture

We're happy to help. You mentioned that you don't have a large family but how many folks do you wish to feed?  Here's a plan for four people:
http://www.almanac.com/vegetab...
Also, we have a Garden Planner that will help you determine the size of your bed and the spacing for plants.  Try it out for free here: http://gardenplanner.almanac.c...

The links were very helpful,

The links were very helpful, thanks!

what size wire mesh should be

what size wire mesh should be putdown to keep gophers out of a raised bed

Hi Greg, 1/2-inch hardware

The Editors's picture

Hi Greg,
1/2-inch hardware cloth is the best choice. Some hardware stores may have something that is called gopher wire.

I'm getting ready to build

I'm getting ready to build raised beds for my front yard. Because they'll be in front, I'd like them to be more aesthetically pleasing and paint them white to match the house trim. But I'm not sure what paints are safe to use, if any. Most eco-friendly paints I've seen are interior only. Do you know of any, or can recommend any, that are exterior paints and are also safe for the garden? Thank you!

Hello! I want to build a

Hello! I want to build a large cedar garden box on concrete and am still a little confused abVout drainage. Do you recommend creating a bottom out of slats and landscape material and blocking it up? Or just giving it a layer of gravel on the bottom? If I give it a layer of gravel, do I still need to block the wood up?
Thanks!

Lots of people do put raised

Lots of people do put raised beds directly onto concrete these days, but I’m not sure it’s the best idea. Here's a solution though: The easiest way to ensure drainage when putting raised beds directly onto concrete is to cut some small holes in the sides of your raised beds at the bottom to allow excess water to escape. You might want to line the beds with landscape fabric before adding your growing medium to stop the soil leaking out along with the water.

I've been planning a raised

I've been planning a raised bed for ages, but it's been repeatedly put on hold because money is an issue right now. However, I've found a warehouse near me that routinely has lengths of untreated pine available for free. Can you tell me:
How long will entirely untreated pine last?
How much will lining the box with plastic prolong the life of the boards?
How long would treated the boards with a food-safe sealer prolong the life of the boards?
I live in a moderately dry climate, if that effects anything. Thanks for your help!

The lifetime of untreated

The Editors's picture

The lifetime of untreated pine really depends how thick it is. Thicker wood will obviously take longer to rot. I’d expect you to get a minimum of 5 years out of untreated pine (unless extremely thin), and perhaps up to about 10 years if it’s quite thick (e.g. 2” x 6”).
Using a plastic lining will avoid having damp soil against the wood and will extend the life of the boards -- how long for will probably depend on the type of plastic used. On your question about treating the boards: Again, it would depend on the treatment used. The product should state how often your wood will need to be re-treated, which may give some indication of its lifespan.

The area where I'd like to

The area where I'd like to have a raised garden is full of tree roots and stumps. It was a cedar grove we cleared had cleared for a garden. Do we need to work up the soil or can we put beds over the existing soil and the roots of plants such as tomatoes will be able to grow deep enough? I have been composting with worms, saved boxes and newspapers. Plan to use the cedar logs for the beds. We could have someone come in and pull out the stumps and break up the soil to help with the old roots. Some of the soil looks really good while most is orange sticky clay and very rocky. I don't think we can dig by hand or till with all the roots and stumps.

If the trees are dead, then

The Editors's picture

If the trees are dead, then they will rot down. It’s possible that they might ‘rob’ nitrogen from your soil as they rot, so you might find your plants need some additional nitrogen fertilizer, but otherwise it should be fine as long as you use a good rich growing medium. If the roots are attached to living trees, then you will probably find that the roots not only suck up nutrients and water intended for your vegetables, they also invade the beds. Raised beds are a great solution where the underlying soil is very difficult to work, and cedar makes great wood for raised beds; it’s very long-lasting. About 12 inches should be deep enough for most vegetables, but for root crops you might want to build a deeper bed. 

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