Raised Garden Beds: How to Build

Credit: Alabama Cooperative Extension System
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Raised garden beds are fairly easy to construct and even easier to maintain. Here is advice on how to build raised garden beds for your backyard.

Benefits of a Raised Garden

  • Ideal for smaller spaces (versus a conventional row garden)
  • Great for rocky, poor, or abused soil
  • Produces a higher yield for the area, thanks to better drainage and deep rooting
  • Allows for a longer growing season, since you can work the soil more quickly in the spring in frost-hardened regions
  • Makes gardening easier; for example, intensive planting creates shade mulch to keep the weeds down

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Comments

Is it recommended to install

By C. Mart on August 17

Is it recommended to install a drainage system in a concrete block raised bed to prevent the creation of a mud pit?

Raised beds tend to dry out

By Almanac Staff on August 20

Raised beds tend to dry out relatively quickly, and are often used to make it possible to grow a garden where soil drainage is poor, so you should not normally experience problems with drainage in a raised bed. Make sure to mix the soil below with the bed with the soil you’re adding to the bed to prevent the water sitting on top of the garden soil, especially if you have very heavy clay soil. If you're worried that the water will pool on top of it you could leave a few small gaps between the blocks, or drill some holes in them, to let the water escape.

We want to put raised beds in

By ShaneS on August 11

We want to put raised beds in the backyard and have septic tanks back there somewhere. The grass grows very well over the tanks - would a raised bed be a mistake over the tanks?
Thanks for your advice.

This is a bit of a grey area

By Almanac Staff on August 14

This is a bit of a grey area so we'll advise you best we can: There is a risk of contamination from growing near septic tank leach fields as it’s not always easy to know if the system is working perfectly. As long as the system is working perfectly then you should be able to grow a some edible crops above it, however it’s generally thought that raised beds can reduce the evaporation of moisture from the soil, which isn’t good for the system.

Definitely avoid growing root crops and perhaps leafy greens near a septic tank. Fruiting vegetables such as tomatoes whose fruit is held high above the soil surface should be fine. Personally, I’d consider planting shallow-rooted, pollinator-attracting flowers in the septic tank area instead.
 

I am building a raised garden

By elephantlover

I am building a raised garden and wondering if i should put some sort of material under the soil? I am afraid the grass will shoot up through the soil if I dont? What do you recommend?

If placed directly onto

By Almanac Staff

If placed directly onto grass, it’s possible that grass and weeds will grow up through the bed. A good option is lining the base of the bed with a porous material such as overlapping sheets of cardboard, several layers of newspaper, or landscape fabric to stop unwanted plants growing up into the bed while still allowing water to soak away.

I would like to build a

By ron firestone

I would like to build a raised bed garden on top of an old basketball pad which gets total sun all day long. Would this cause too much heat from the sun heating up the concrete? Thank you, Ron

I wouldn’t be too concerned

By Almanac Staff

I wouldn’t be too concerned about the heat as the raised bed will shade the surface beneath, but I would be worried that the solid surface beneath the beds would cause problems with drainage. You would need to either break up or remove the concrete below the bed, or else make gaps in the sides of the bed for water to escape.

I have been preparing a

By Christmas Tillotson

I have been preparing a portion of our yard this week to start a raised bed vegetable garden. I am using organic soil and seeds, so the safety of my vegetables is important to me. I have the garden next to the house, but have read that this may be a bad thing to do because of possible contaminants. Our house is lead-free of paint, but are there other contaminants to worry about? I guess I should have our soil tested. If I want the organic soil in the beds to be as pristine as possible, should I place a barrier between the organic soil and our current soil? Landscape fabric? Rocks? I'm not sure. Thanks so much for any advice.

Many people do grow close to

By Almanac Staff

Many people do grow close to their house without problems, and it's not something I would personally worry about too much, but if you're very concerned at all I would recommend having your soil tested and seek expert advice on the findings.

Thank you. I did have it

By Christmas Tillotson

Thank you. I did have it tested for arsenic and lead and the levels came back within normal limits.

Also, for the love of Pete,

By Jenoside

Also, for the love of Pete, calling the hard rock-like stuff in your driveway cement is the same as calling a cake by the name flour. It's concrete, of which cement is a component.

Hey, really there's no need

By Tyler_K

Hey, really there's no need for unnecessary ruddiness. But, to be that completely technical guy....

Cement was actually patented in the mid 1800's in Europe and anything from there after of similar mixture in the United States become known as concrete.
Essentially the same thing but known as a different name.
Now It is also true that what we call in the US cement doesn't always have to be of the substance in which was patented in Europe. Similar to the all cactus plants are under the classification of succulents but not all succulents are cactus. We have advanced the word into many other meanings. Such as "rubber cement" or "cement adhesive."

Hence to say, it's a common and reasonable mistake to Americans depending on your generation line I would guess. But to say calling cake by the name of flour is super extreme and can only have the intent to be hurtful and obnoxious. It's a common reality even in the days of 1800's we can say, that flour, and cake, are two separate things. And seeing how you have to mix flour to create a cake makes this example just plan nonsense. You don't need cement to create concrete. Cement and concrete are the same ingredients just mixed to different recipes.

Thank you...
Now please don't purposefully make a comment intending to be hurtful again.

CCA has never been banned, it

By Jenoside

CCA has never been banned, it was a voluntary effort by manufacturers to stop using it in response to public outcry regarding its use in boardwalks and children's play equipment.

http://www.epa.gov/oppad001/reregistration/cca/

An easy way to ensure that your lumber wasn't treated with CCA is that most companies now use copper azole, which turns the lumber green (copper). If your lumber is green, it was not treated with CCA.

I have 20 "storage

By Jensmith777@hotmail.com

I have 20 "storage containers" I got to use as raised bed gardens. They are 32"x 48" and 16" high with 5" gap between ground and bottom of box. They are made with a pressed/composite type wood. They were used to ship auto parts. My ? Is what can I use to paint/protect the outside if them to prevent weathering. The inside I was recommended to line with plastic.

There are many eco-paints on

By Almanac Staff

There are many eco-paints on the market these days for wood; your local hardware shop may stock them, or look online. Raw linseed oil (as opposed to boiled linseed oil, which is mixed with solvents) can be used too. Lining the inside with plastic is a great idea, but if you're extending this across the base remember to make plenty of drainage holes.

Can you use old tires for

By Trish E

Can you use old tires for raised garden beds?

Sure, old tires stacked on

By Almanac Staff

Sure, old tires stacked on top of each other work especially well for potatoes.

I am considering purchasing a

By jrvogel26

I am considering purchasing a 1 inch thick cedar for my garden bed, because I cannot find a 2 inch thick cut. Is 1 inch thick enough?

Consider connecting 1-inch

By Almanac Staff

Consider connecting 1-inch thick cedar boards with 2-inch-long brown screws (sold in most home improvement stores) or 3-inch deck screws. Drive screws through the side boards of the beds into four-by-four vertical posts in each corner.

My lawn is Bermuda grass. A

By Danny D.

My lawn is Bermuda grass. A first try at a raised bed (after digging out a place in the back lawn) resulted in Bermuda eventually taking over the bed. It loves water! An old blacktop pad seems a good spot for the bed if the soil is deep enough. There's enough sun. But, will that work?

Sure. You can put a raised

By Almanac Staff

Sure. You can put a raised bed on blacktop. Add a layer of gravel to the bottom to prevent the soil from leaking out with the water.

How thick should the layer of

By lola898_99

How thick should the layer of gravel be? Doing my bed on cement...I'm assuming the gravel still applies? Thanks so much!

HI - I'm very concerned that

By Deborah F Edwards

HI - I'm very concerned that I made a huge mistake. My husband and I made some planter beds. We live in the NW, lots of rain, and bought regular wood (not pressure treated). My husband painted the wood to protect it from rotting, first with a sealer and then with indoor/outdoor paint. Will this be OK? I'm concerned about chemicals, but it's done and has been filled with a 50/50 blend of soil. Your thoughts would be appreciated.
Thank you

It's better to leave the wood

By Almanac Staff

It's better to leave the wood unpainted or use linseed oil. Some gardeners line raised beds with plastic to protect the soil from chemicals.

Actually a question. Live in

By Zoebearski

Actually a question. Live in Southern California looking for compost is it safe to get the stuff they have at the county type provided dumps? Or is that not safe?

Potting soil-are they all the same or are their brands or local places in San Diego that have better stuff?

If the composting process is

By Almanac Staff

If the composting process is done correctly it will eliminate the risk from any pathogens or other contaminates. If the compost looks and smells good it should be OK to use.

There are many types of potting soils for different uses. One guideline is to look for potting soil that is even in texture. Avoid soils that are heavy and have large clumps of dirt or contain big chunks of wood or bark.

You can make your own potting soil. See our blog at almanac.com/blog/gardening-blog/make-your-own-potting-mixes

Good day I just moved into a

By cecelia bourque

Good day
I just moved into a new house and looking forward to planting my raised garden, this will be my 3rd one. Our yard is slopped do you have any tips or guidance for slopped raised gardens. Thank you. Now if the snow can go away lol

Hi Cecelia, The raised beds

By Almanac Staff

Hi Cecelia,

The raised beds need to be level to ensure even water distribution, so when you build the beds the sides need to be tapered to fit the sloping ground. Look for sloping raised bed designs online and you'll find several good how to web sites.

 

Looking for some assistance

By Daenna

Looking for some assistance in building a raised garden bed directly on cement. I'll be using the landscape blocks that fit into each other with no mortar. My question is.... I thought I could just put the blocks directly on the cement but after purchasing them, I was informed they need to lay on a minimum of 1 inch of gravel/sand mixture. This seems like a nightmare as now won't sand and gravel continuously leak out of the bottom of my garden bed??? Not to mention cosmetically having the block stand on 1 inch of gravel seems would look a little odd? Apparently this is crucial so the blocks have settling space?? Can anyone confirm or deny this for me? Or share your experience with raised beds directly on concrete??? Thanks!

We have heard from gardeners

By Almanac Staff

We have heard from gardeners who have put blocks directly on cement and then added gravel to the bottom of the bed for drainage and soil on top. The water will find its way out under the blocks with no problem.

Hello, Please tell me if you

By Jillian Marie

Hello,
Please tell me if you have any special tips for southwest Florida raised bed veggie garden. Heat is a factor and wondering what veggies might do well here.
Cheers.

Soil in raised beds warm

By Almanac Staff

Soil in raised beds warm faster and dries out more quickly than soil at ground level, so you need to remember to water the raised beds more often. Bush type vegetables, such as tomatoes, cucumbers, or beans, grow well in raised beds. Install trellises on your beds for vegetables that need support like cucumbers and squashes.

hi , i have used clay tiles

By Prema

hi ,

i have used clay tiles to make a raised bed in my garden . i would like to know the possible drawback in doing this . i am a beginner in gardening so i would be glad to know more .

Clay tiles work great for

By Almanac Staff

Clay tiles work great for raised beds. Clay sometimes soakes up some moisture so make sure to water regulary and check the soil. Good luck!

Numerous questions: The

By Ken Werner

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,

By Almanac Staff

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

By Sandy R

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

Here's a reference article on

By Almanac Staff

Here's a reference article on different materials to consider for raised bed gardening (pros and cons): http://www.caes.uga.edu/Publications/pubDetail.cfm?pk_id=8041

I really want a raised bed

By Toni Franco

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

By Almanac Staff

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/how-use-raised-beds-your-garden

Hello, This is a very

By IanScott

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

By GeorgeB

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

By penny adkins

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

By Aleisa

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

We've revised this article to

By Almanac Staff

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

By Criley

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

By r.r.gendron

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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