What is Raised Bed Gardening?
A raised bed is simply a freestanding garden bed built on top of existing soil or grass and is used for no-dig gardening. It generally is framed in to keep the soil confined and can vary in size. A path is built alongside the garden bed; stepping into the bed is strongly discouraged to keep the soil from compacting.
Why Garden in a Raised Bed? (Pros)
We are big fans of using raised beds in our garden. The soil in raised beds warms up a bit faster than the ground around it allowing us to plant a little earlier. Since we are at a relatively high elevation (at least for our area) this helps. Spring comes a week or two later for us than just a few miles away in the valley, so we appreciate the warmth of our raised beds.
All of our garden is no-dig, but about 10% of it does not have frames around it. Those beds get more weeds, especially around the edge because it’s inevitable that our feet will stray into the beds even if we try to stay on paths. Weeds tend to love compacted soil, which is why weeds sprout up where we step.
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And that leads into the next pro of gardening in raised beds. Not ever stepping onto our beds means that the soil does not compact. No soil compaction means not only little to no weeds, but we never have to dig our gardens because the soil remains loose. The two things that make gardening difficult are weeding and digging. Raised beds eliminate both, for the most part (yes, I do get occasional weeds).
The soil in a raised bed also drains well ensuring that the soil is aerated. It also helps to prevent disease. Part of our garden is in an area that will hold a few inches of water when we get a lot of rain. Being raised, it has never been a problem.
In addition, raised beds are ideal for areas with rocky soil since you are building on top of that soil. And since you are building your garden from scratch, you can assure quality soil; it won’t matter if your soil is poor to begin with.
Cons of Gardening in a Raised Bed
While I pointed out that a benefit of gardening this way is that we can plant earlier since the beds warm up sooner, if you live in a hot, dry climate this can definitely be a con. Raised beds can get warm, and have great drainage, both of which will work against you in a hot, dry climate.
Gardening in raised beds can be expensive to start. But a frugal person should be able to scavenge all the materials needed. And re-using materials meant for the dump is actually a plus.
I am not without talent, but if the bed construction were left to me we probably would not have beds with frames. I just don’t have the skill (or strength) required to build the frames. But, as I’ve mentioned, we do have a few beds that are raised, but not framed, like our raspberry patch. So, even without skill or resources, raised beds are still possible.
Purchasing already built raised beds in another option, although the cost can be prohibitive if you have a large garden like ours. We have over 20 beds with frames and several more without. We’ve built ours a few at a time to keep the costs manageable.
Here are a few options for purchasing:
Galvanized Steel Garden Kit 80Lx40Wx16H
Wooden Garden Bed Planter 96Lx24Wx10H
U Shaped Wooden Bed 92.5Lx95Wx11H
The last con that I can think of (comment if you have more) is that occasionally I’ll see a beautiful garden full of lovely curves, and wish that our garden was beautiful in that way. It does have it’s own beauty, but there really is something about flowing lines that make a garden attractive. Since we use wood, the lines in our garden are all straight. Of course, using rock or brick would allow for curves.
How Deep Should a Raised Bed Garden Be?
There is really no one right answer to this question. Some raised beds are deep enough for someone in a wheelchair to reach. Most are much shallower. And if built properly the roots of your plants will grow into the soil below the bed; they are not limited to just the depth of the frame you’ve built.
Most of our beds are 8 – 10″. If I were growing on top of very rocky soil, or sometimes wet soil that needed better drainage, I would prefer 12″ – 18″ (never build in a swampy area – even a raised bed won’t improve that).
What Do You Put in the Bottom of a Raised Bed?
My recommendation is to place cardboard, or a thick layer of newspaper (no shiny colored pages) on the bottom of your bed. This will kill any weeds or grass growing there. The plant material and cardboard will eventually decompose, adding fertility to your garden.
Be sure to thoroughly wet the cardboard or newspaper to help speed decomposition before adding any other materials to your garden bed.
Should You Line a Raised Bed?
With a liner that does not decompose you are essentially building a very large container garden. And container gardening requires more fertilizer, and more attention to proper watering.
I prefer a liner like cardboard which kills weeds, and which decomposes, building soil and allowing the roots to grow into the soil below the garden bed. I’ve also used old jeans, cotton fabric, and an old wool rug. These work the same as cardboard, decomposing to build soil and attract worms.
Green Upside has a good article about lining a raised bed with lots of pros and cons.
Do I Have to Remove Grass Under a Raised Bed?
You absolutely do not have to remove grass before building your garden. In fact, the grass that you leave will decompose and build good soil. You do need to cover that grass, however, to assure it does die and decompose. See the section above on what to put in the bottom of a raised bed.
How Do I Fill a Raised Bed?
For some reason, building a new garden bed and filling it is one of my favorite parts of gardening. I guess I like the process of creating.
There are several options for filling your new garden bed. But keep in mind that the vegetables you grow in your garden will only be as healthy as your soil. You want your soil to be loose and crumbly and able to hold water.
You could purchase good quality topsoil for your garden, or better yet, mushroom soil. But I highly recommend filling your bed by building a lasagna garden. Also known as sheet composting, a lasagna garden is built by layering organic materials which eventually will decompose into wonderful garden soil.
Lasagna gardens can be built with any number of materials:
- Partially decomposed tree limbs or twigs – best used as a bottom layer
- Leaves – chopped are best
- Manure – fresh is ok if you are building the garden in the fall, but otherwise use well-rotted manure, since fresh manure will burn the roots of your plants
- Weed-free hay or straw
- Alfalfa hay which contains a growth hormone that plants love
- Coffee grounds – just don’t overdo it – coffee filters are ok, too
- Grass clippings – either fresh or decomposed
- Shredded newspaper
Don’t worry if you can’t find all of the “ingredients” Do your best and build with what you have.
Everything you need to know about building a garden in this manner is in my post Lasagna Gardening: an Easy and Productive Way to Garden.
What is a Good Size For a Raised Bed?
The length and width of a raised bed can vary, of course, but it should never be more than 4′ wide. Anything wider will make it difficult to reach all areas of the garden and you’ll end up stepping into your garden bed. This defeats the purpose of having a no-dig garden because you will compact your soil by stepping into it.
A bed that is too long will cause similar problems. You will be tempted to walk across the garden rather than around in. I would certainly not make a bed longer than 12′.
Where Should Raised Garden Beds Be Placed?
A raised bed for vegetables has the same requirements as any other garden.
Most vegetables need full sun, so locate your garden where it will get at least 8 hours of sun. Cooler weather crops such as lettuce and spinach don’t mind less sun and may not bolt (go to seed) as quickly when the weather warms.
A spot close to your kitchen should be your next consideration. I frequently run out to the garden for herbs or another tomato for the salad, etc., when I am cooking. Having it close by is a convenience.
If you are new to gardening, you will appreciate my post Organic Vegetable Gardening 101.
And if you are concerned whether your property gets enough sun, you can always track shadows for a full day. This will help you to determine where you get the most sun on your property. Full instructions can be found at How to Track Shadows So You Can Choose the Best Spot for Your Garden.
What Kind of Material Should I Use to Build my Bed?
Frames for raised beds can be made from all kinds of materials. Wood is common, but frames can be made of galvanized steel, bricks, stone, plastic, cinder blocks, or even tree trunks or limbs.
Empress of Dirt has some good information on choosing the best wood for raised beds.
Is it Ok to Use Pressure Treated Lumber for my Garden?
At one time I would have answered this question with a quick “no” because pressure treated lumber used arsenic to protect against rot.
But how wood is pressure treated has changed over the years, and many say that it is safe for use in gardens. Copper or chromium are now used to protect wood. Plants are able to absorb these preservatives, but is considered low enough to be undetectable.
Please do your homework so you can decide for yourself whether to use pressure treated wood in your garden. Cedar is a good alternative if you don’t want to use pressure treated lumber and don’t think that construction grade lumber will hold up. It can, however, be costly.
How to Build a Wooden Raised Bed Garden Box
Most of our beds are 4’W x 12’L x 10″H. The sides of the beds are 2 x 10s and the top is capped off with a 2 x 4 shelf for stability. This shelf is also great for sitting or kneeling. The box just sits on the ground; several of our boxes are 5 years old with no sign of rot.
- 2 pieces of 2 x 10 x 12 construction grade lumber
- 2 pieces of 2 x 10 x 4 construction grade lumber
- 2 pieces of 2 x 4 x 12 construction grade lumber
- 2 pieces of 2 x 4 x 4 construction grade lumber
- 8 scrap pieces of 2 x 4 or 2 x 3 approximately 12″ long construction grade lumber
- 54 3″ epoxy coated deck screws
- a drill
Start by making sure you are working on a flat surface to ensure that your finished garden box will be perfectly on square.
Make a rectangle with your 12′ and 4′ 2 x 10s by screwing the boards together with 3″ epoxy coated deck screws (these are self drilling, so you will not need to drill a hole first), using 4 screws at each corner.
Attach the scrap pieces of 2 x 4s by screwing them to the inside of the 2 x 10s. These will help to support the 2 x 4 shelf that will be placed on top of the 2 x 10s. Place one support on each 4′ section, and evenly space 3 supports on each 2 x 10, using 2 screws for each support.
Now use screws to attach the 2 x 4 shelves to the top of each 2 x 10. These will keep your box from bowing.
If you need a good visual before building your raised bed garden, watch One Yard Revolution’s video below.
Your garden box is finished and can be moved into place in your garden. You can now lay down cardboard and fill your garden.
To learn how to build a garden that builds healthy soil, be sure to check out my eBook The Art of Gardening: Building Your Soil.
You really can become a better gardener, and you really can grow healthy, nourishing produce. It’s all about the soil! Click here to learn more.
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