preparing a raised bed garden

6 things to think about before preparing a raised bed garden

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Are you planning to build and/or install a raised bed? I like to emphasize that raised beds can go anywhere that gets six to eight hours of sunlight a day. And they can be any size you like. However, for the purpose of this article, I’m going to talk about the standard rectangular raised beds that are generally built from untreated, rot-resistant wood (like Niki’s amazing raised bed setup) or concrete blocks, as well as what you might want to think about when preparing a raised bed garden.

When I made my first raised beds, these are a few tips I gathered, as well as things I wish I had thought about beforehand.

Things to think about when preparing a raised bed garden

1. What size will it be?
Raised beds are generally three to four feet wide by about six to eight feet long. This allows you to easily reach into the raised bed from the side to plant and dig and weed, without having to step into the garden where you risk compacting the soil.

The height can also be important. If you are putting your raised bed on a hard surface, like a driveway, or over hard-packed soil, you want to make sure it’s deep enough for plants (especially root vegetables like beets and carrots) to root. If it’s too shallow those roots will reach down into that subsoil (or hard surface) and hit a brick wall. I usually recommend at least 10 to 12 inches.

2. How do you pick the perfect spot?
When preparing a raised bed garden, location is everything, but it doesn’t have to be your backyard. Your raised bed could go in a sunny side yard, your front yard, or even your driveway.

You’ll want to make modifications if you have a slope and assess whether the area drains well. Here are some tips for planning where to put your raised bed.

3. How will you get rid of grass?
Good question because this is a common concern. If you’ve ever tried to cut out and lift sod, you know what an enormous task it is. An easier way to get rid of grass is to outline the space and cover it with a layer of cardboard and cover that with a layer of soil. The grass will break down and voilà! A new garden site. Doing this in the fall will allow everything to break down over the winter.

4. Do you want to install irrigation?
If you want to set up a whole drip irrigation system with a line running from your tap or rain barrel, you might want to do this before your raised bed areas are finished and filled. That way you can run hoses under pathways or layers of mulch, and adapt the bed around where the hose attaches to the irrigation system.

5. How much soil will you need and what kind?
There are some handy soil calculators out there that will help you determine how much you need to fill your raised bed, like this one from Gardener’s Supply Company.

As far as type of soil, I like to emphasize buying the best quality that you can afford when preparing a raised bed garden. When I had multiple raised beds to fill, I ordered triple mix from a local supplier (after chatting with them on the phone about my options) and top-dressed it with organic vegetable compost. I like to recommend leaving some in reserve to replenish your raised beds throughout the season.

6. Should you stake the sides?
One thing I wish that I had done when I built my first two raised beds is install a couple of midpoint stakes to prevent the beds from shifting over time. This is one of my number one raised bed tips!

For more information on gardening in raised beds, check out the following articles: 

Do you garden in raised beds? Share your experience in the comment section below.

photography by Donna Griffith for Raised Bed Revolution

preparing a raised bed garden







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32 Responses to 6 things to think about before preparing a raised bed garden

  1. linda wong garl says:

    When I built my raised beds over 10 years ago…I used landscape fabric but made sure I put the edge of wood on top of the fabric so the grass would not grow into the bed…Also, used cardboard over the top of the landscape fabric…never, ever had a problem with grass or weeds growing through….do those precautionary steps and you will be a happy gardener!!! I heavy bolted the corners and reinforced the inside with a 2 by 2 piece of wood to bolt into…solidly cornered…so they have been perfectly intact …the extra care in the beginning is a long term plus!!! Don’t forget to rotate crops each year…from bed to bed! And replenish with new compost or raised bed organic nutrients ….

    • Tara Nolan says:

      Great tips, Linda, thank you for sharing with our Savvy readers!

    • Carolyn says:

      i want to start a raised beds for next yr so put the weed barrier fabric down,make the boxes, but what do u fill the boxes with besides top soil? and what do u add to the top to prevent the plants from drying out? i want to make mine organic what can u use for bugs? and what flower do u use to keep animals snakes away thank u

  2. Thomas Brophy says:

    You write that you have filled new raised beds with a “triple mix.” After many years of gardening, I have never heard of such a mix, and don’t believe it is offered by those businesses offering topsoil for sale. So, if you could delineate the components of triple mix, perhaps it could be replicated by gardeners without access to it.
    Thanks.

    • Tara Nolan says:

      Hi Thomas,
      I can’t find the ingredients on the site where I bought my soil (it looks like they are redesigning), but generally it’s a mix of top soil, peat moss, and compost. I called ahead of time and spoke to an employee and felt good about my choice. Mel Bartholomew, who perfected the square foot gardening method, recommended 1/3 perlite or vermiculite, 1/3 peat and 1/3 compost and within that compost, he said to include 6 different types of compost.

    • Thomas Brophy says:

      Hi Tara, thanks for your reply. Sounds like a good general mix, except holy, holy 6 types of compost? Jeez! Lol. I’m thinking probably many roads lead to Rome, so to speak. So, my general compost, of which there never is as much at the end as I had hoped, plus straw duck bedding and manure, plus my home-made fertilizer of fish frames, heads and guts, molasses, kelp, etc. hopefully will do.
      Thanks again.

  3. I am planning to grow vegetables as grocery are becoming expensive and it is healthy to have your own grown food. In modern time un-ethical fertilizers are being used in agriculture and to protect our family from this poison, raised bed garden gardening is important.

  4. Tara Nolan says:

    Hi Thomas, I know! That is a lot of different types, but your mix sounds like it’s probably nutrient-rich and just as effective! 🙂

  5. Tyler says:

    I like what this you recommend about buying the best soil you can afford. It makes sense that soil can make all the difference for a garden, especially one without ideal conditions. I’ll have to remember this for my garden because I’m going to completely redo the soil and making sure it’s high quality would be helpful. Thanks for the post!

    • Tara Nolan says:

      Best of luck with your garden, Tyler! I always recommend top-dressing your raised bed with an inch of compost mid-season to restore some nutrients, as well!

  6. Miriam Breezee says:

    Just rented a raised bed at a community garden.
    Added more rich soil. The bed itself has alot of bugs. Should I do anything about this or go ahead and start planting.
    Newbie Gardner! TIA

    • Tara Nolan says:

      Hi Miriam, it’s hard to say what you should do as there are many beneficial insects that live in a garden – not just bad guys! I would go ahead and start planting. And if you see anything happening to your plants, post a photo of the offending insect to a Facebook group to help you identify. That’s what I did recently when my sister had a crazy beetle on her black-laced elder. I discovered it was a bad guy!

  7. Marc says:

    I think you also have to consider what materials to build the raised beds from. If using wood, avoid pressure treated (despite assurances that the new type of pressure treated lumber is not toxic) and consider a more durable wood such as cedar or redwood. I lined my new cedar raised beds with plastic on the inside (just the sides not the bottom) to try and keep the soil from direct contact with the wood. My last raised beds that I replaced with the new cedar ones were just made from pine 2×6 lumber and rotted away in less than five years. The other issue is the corner joints fell apart as the wood rotted so my new beds have extra 2×4 reinforcement on the corners and at regular intervals along the long sides.

    Or if you can afford it use stone. But be aware that the beds will not be easy to move whereas with wood beds you could move them if you had to or at least disassemble them and move them in pieces.

    • Tara Nolan says:

      You are absolutely right! I recommend using rot-resistant wood, like cedar (my Savvy colleague Niki uses hemlock). At the time of writing this, my cedar raised beds are almost six years old and still in great condition!

  8. Shiv Iyer says:

    Just read your fantastic book,”Raised Bed Revolution”.
    Questions:
    1. Since my raised bed (4′ x 12″ x 1′) will be on grass, I will put cardboard on the grass to kill it. If I start now, will it be good for planting in say March/April 2018?
    2. At that time would I still need to add landscaping fabric at the bottom of the raised bed?
    Thanks.

    • Tara Nolan says:

      Hi! I’m so glad you like the book. 🙂
      The cardboard might not have totally taken care of the grass, but it should be on its way. I would say landscape fabric is necessary if you are fighting nasty weeds with deep roots, like bindweed (the bane of my existence on one side of my property), but if it’s just grass underneath, I would just let that cardboard and grass break down under the soil you place on top!

  9. Jen says:

    Hello!
    I have always wanted a garden but the money is never there’re to create a raised bed, I have a feral cat colony so I really do want a raised bed to ensure there’s no kitty waste in my veggies! I would fence it off with some netting I have. My question is, with no really funds to purchase wood I thought I would use left over fence boards form a couple of seasons ago. The problem is that it is treated lumber. Is it safe to use since it has been outside a couple or years? I could look into pastic lining but as I said I don’t really have money to invest and i’ll habe to purchase soil and plants too. Thanks for your post it’s very helpful 🙂

    • Tara Nolan says:

      It’s hard to say if the chemicals have perhaps already leached out of the wood, so I would be cautious planting food if you haven’t lined the inside of the raised bed with plastic.

    • Kelly says:

      What you have should be fine. The chemicals in treated lumber don’t leech that much into the soil, and what little does typically stays in the soil. If it’s too much it will kill the plant long before it reaches a level high enough to hurt you. My beds were made with treated pine and I researched my face off on the topic, and read many studies and many opinions. If your lumber wasn’t manufactured before 2003, it’s fine. I don’t know if they have anything like this where you live, but here in Syracuse you can fill up your trunk with compost made from local yard scraps and food waste for five bucks. Mix that with a big bag of peat moss and some perlite or vermiculite and you’ll have fantastic soil to start growing in! You don’t have to have piles money to have a great garden. Just a will to get it done. 🙂

    • Laura says:

      Kelly had some great suggestions. Another idea, if you have a small amount to invest, is to look at your local hardware store for cedar or redwood fence pickets (6′ dog ear or flat top…I cut the dog ears off mine). I was able to make a 3’x6’x11″ raised bed for $25.00 (hardware and 2x2s for the joints included in that price).

    • Tara Nolan says:

      Hi Laura, That sounds like a great idea! Thank you for sharing it here. 🙂

  10. Lydia Orlando says:

    I have a question about the soil in the raised bed. Should it be removed and new soil put in. It seems like my plants are not doing as good as they used to about 5 years ago. I do put manure in the bed and mix it into the soil that is there.

    • Tara Nolan says:

      Hi Lydia, I don’t recommend removing soil, I usually amend my raised beds with a few inches of compost. I would suggest trying a manure/compost mix or maybe just compost this season!

  11. Jenny says:

    Hi!
    I am so excited to start my raised beds this year!! I am unfortunately starting late down here in GA where it’s already so warm. I wonder, in terms of grass, I am looking to build in a great section of our yard. What do I do about the grass? Could I till it up or should I put something down? I am against the use plastic in our garden, however. What would you suggest?
    I also wonder, since it is so warm, could I just plant seeds and let them go or should I sprout them ahead if time? It’s already in the 70’s here!
    Thank you so much

    • Tara Nolan says:

      Hi Jenny, If it’s late in the season, I would recommend putting cardboard down over the grass and covering with a layer of mulch. Now usually you would leave it for a bit so the grass can decompose, but I say just put the raised beds overtop of the cardboard and mulch and fill with soil! You should be fine direct-sowing seeds in the garden at this point. Check the seed packets to see how warm the soil has to be to plant, but I feel like you should be good. You are SO far ahead of where I live!

  12. Tara Nolan says:

    Hi Carolyn,
    I would make sure that you amend the soil with compost. You could add a light mulch, like straw, which will keep the weeds down and help retain moisture. There are some great charts online that show you what to plant that will attract the “good guy” insects to take care of the bad guys.

  13. Allison says:

    I am adding raised beds to my garden. What height do you recommend if placing on grass with a cardboard/mulch bottom. These boxes are going to be used for tomatoes. Our existing garden has become the shaded area of the yard, the neighbors planted a tree.

  14. Laurie Geiser says:

    I am looking to try a couple of raised beds or containers this year with hopes to do much more next year. The only open, sunny spaces I have are over my leach field, and I am told that I cannot grow food plants there. So, can I grow in large containers that do not allow any root contact with the actual hard clay dirt? If so, do they need to be deeper than the 10-12 feet you advise for raised beds? Should I use a couple of inches of gravel at the bottom for drainage to keep the soil from being too wet? Sorry so many questions. This is all very new to me.

  15. Cynthia Irving says:

    Can I use a tarp under my raised beds to deter weeds and grass from growing. I was thinking I could poke holes in it for drainage?

    • Tara Nolan says:

      Hi Cynthia, I fear that a tarp wouldn’t drain well, even with holes. Also, the weeds will then be able to grow up through the holes. I would recommend landscape fabric, which is permeable. 🙂

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