How to Build a Raised Garden Bed

Planning, Building, and Planting a Raised Garden Bed

January 10, 2020
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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) coconut coir (to improve drainage)
  • 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

Leave a Comment

Numerous questions: The

Numerous questions:

The backyard is sand and crabgrass, so I'm thinking of using cement bricks and creating 4 raised beds in a small area (25x40ft) to create a Victory Garden:

(1) what is the dye used in cement bricks and is it nontoxic?

(2) would it be safer to use clay bricks?

(3) if cement raises the pH in the soil over time, how do I counteract that?

(4) does mortar affect soil pH and how do I counteract that?

(5) how do I kill crabgrass without using a toxic method like pouring on gasoline and burning the crabgrass, which will contaminate the sand underlayer (will be using mulch and potting soil in the raised beds)

(6) what is the minimum depth for growing potatos, carrots, tomatos, beans, broccoli, lettuce, collard, bell peppers, garlic, leeks, scallions - or is that info available on the website?

I'm not in a rush to hear responses since this won't happen until Spring 2014.

Thank you to everyone for your responses.

Hi, Ken, Here is some advice,

The Editors's picture

Hi, Ken, Here is some advice, courtesy of our Almanac Garden Planner App experts:
1) + 2) There are lots of conflicting opinions on this, and it will depend on the type of dye used on the cement bricks you buy - I can only advise you to call the manufacturer. If you're concerned you can use clay bricks, or line the inside of the bed, and underside of the bottom row of cement bricks, with plastic to prevent any possible leaching.
3) + 4) Cement and mortar can raised the pH over time (making it more alkaline) but this does take a very long time - I would only be concerned if you're growing acid-loving plants such as blueberries. Normal mulching using leaves, pine needles etc for acid-loving plants should be sufficient, or you could also incorporate sulphur chips into the soil (not for other fruits or veggies though).
5) The best way to suppress the crabgrass within the bed would be to lay a permeable membrane down on the base soil (eg landscape fabric, which can be bought from most gardening stores) and install your beds on top. The permeable membrane will prevent the crabgrass from growing up into your bed, while still allowing free drainage.
6) About 12" depth is sufficient for most veggies (even potatoes, since normally you hill up earth around potatoes rather than planting them particularly deeply), but if the bed is very small it might be better to allow for a bit more, especially if using a permeable membrane at the base. A larger, deeper bed will also retain moisture better and cool down more slowly in the fall than one that is small and shallow.
I hope that helps!

What about hardiplank or

What about hardiplank or composite decking scraps? Can these be used for raised beds? Are there any concerns?

I really want a raised bed

I really want a raised bed garden, been wanting one for years. I am very worried about the wood because of the chemicals leaching into the veggies. Cedar is very expensive so we bought just pain cheap wood; is this safe? I know it will rot but I thought if I could maybe stain just the outside and then line the inside with plastic would this be safe, because how safe is plastic? Thank you,Toni

You certainly don't need to

The Editors's picture

You certainly don't need to use cedar. You could use regular pressure-treated lumber that doesn't rot. Cedar is more expensive but it has natural oils to prevent rotting and will last many more years before they need replacing. You might find our video helpful! http://www.almanac.com/video/h...

Hello, This is a very

Hello,
This is a very informative page. Thank you.
I am building a long, raised cedar planter box for use as a vegetable garden. I am concerned about the longevity of the wood over time. I am curious to know if there are any safe liners that you would recommend to prolong the life of the cedar.
I have looked at various pond liners as a possibility, but the information on the Internet seems inconclusive regarding safety.

Again, thank you for creating this online resource.

Cedar is a naturally

Cedar is a naturally rot-resistant wood. Eastern red cedar (Juniperus virginiana) is the most rot resistant and will last for years even when in contact with soil. However, it is more expensive. Lining the inside of the garden bed with 6-mil black plastic may prolong the life of the lumber.

I am 51 yrs old and planting

I am 51 yrs old and planting gardens my entire life and always wanted to try a raised bed, so this year I AM having an underground and raised garden.

oops...u shouldn't use

oops...u shouldn't use treated wood.

We've revised this article to

The Editors's picture

We've revised this article to be clear. The pressure-treated wood with arsenic has been banned. Pressure-treated wood sold today is certified as "okay" by organic growers. Still, if you feel uncomfortable, there are alternatives mentioned above.

I just built a raised bed for

I just built a raised bed for the first time. I used 2x12 pressure treated pine. A 4x8 foot bed with 2x4s around the top edge for easy seating while gardening. My wife and I are in our 60s and retired. This is a great way for seniors to garden and enjoy the benefits of the exercise and the great taste of on-the-plant ripened vegetables.

read ur article about raise

read ur article about raise bed, i'll be doing raise bed this yr,since i'm getting in age. i'm 74 & in good health, thanks old farmer's almanac.

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