Raised bed height?

hobbyist3May 5, 2010

I am building an 8 x 4 foot raised bed.

How high should it be?

I have done umpteen internet searches, and answers vary.

I would like to plant vegetables, lots of veggies of all kinds.

My backyard is typical suburban backyard with bluegrass. Perhaps the soil was amended to some extent when the house was built 10 years ago.

Answers to the following questions also vary -- any insight would be appreciated:

Should I dig up the turf underneath before filling raised bed with top soil?

Does it matter if the bed is on not quite level ground?

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gjcore(zone 5 Aurora Co)

An 8x4 bed is not big enough to grow all kinds of veges but it is a start. I'm guessing that you are somewhat new to gardening and the first mistake most newbies make is to plant too many things.

How high it should be varies but 6 to 12 inches is common.

It probably would have been better if you started smothering the grass sooner but it's certainly not too late. So maybe it would be better to turn it over and then add your topsoil and whatever amendments as needed.

You should probably make your beds fairly level. So depending on what you're using as a border you probably need to do some digging.

    Bookmark   May 5, 2010 at 10:41PM
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I'd say at least 6" high but you can choose to go deeper if you'd like. Mine are about 15" high but I also have some that are less.

You'll want to level the perimeter but I wouldn't worry about the ground otherwise being level meaning level the box, leave the middle. You might want to sort of break up the ground - loosen it with a spading fork- then lay a thick layer of newspaper or cardboard to smother the grass underneath then fill. You'll want to add some organic material or compost to your soil. There are a ton of options what to do there too :-).

Here is a link that might be useful: Tales of a Transplanted Gardener

    Bookmark   May 5, 2010 at 10:58PM
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Thank you both.

Green bean, Why did you make your beds 15"? That seems on the deep end based on what I have read. I would be happy to go that deep -- just curious whether it improves quality or something.

    Bookmark   May 5, 2010 at 11:32PM
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I did it b/c I didn't think the soil underneath was very good. I also filled my beds lasagna-style so I needed to add lots of material as it would break down a lot during the season. I'm not sure I had to go that deep though, 8-10" would probably have been fine.

I've done some other planting spots (not full-fledged beds, planting "rings") that are only about 6" or so of organic material on the soil. (click the link below to see what I did with those).

Here is a link that might be useful: Rings

    Bookmark   May 6, 2010 at 12:03AM
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Dan Staley

The main issue here is that the more soil you have, the larger water reservoir you have. You will be watering less with greater depth. And raised beds - altho warming up earlier and staying warm later - need to be watered more often. If it were me, I'd do at least12" and it will be less painful bending as well. Your raised bed - depending upon where you site it - may also allow you to do greens over the winter as well. More depth will make that more likely.


    Bookmark   May 6, 2010 at 9:34AM
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I built a 4x8 raised bed last year in my back yard and it's been great. We used 2x8s, so 8" tall. We removed the sod, leveled it out the best we could, and built it. Used posts to anchor it and help level as well, and end caps to help finish the look. Also used deck sealant to protect the wood.

It probably does't have to be level, but it helps. We then dug / turned over the native soil underneath, probably 12" deep. Bought about a dozen big bags of garden soil, added them in, and mixed it all up with the soil that was there before, so probably 18" total, 6" above the ground. Results were amazing. If I think about it, I'll try to upload a picture so you can see it, but I'm sure you could find plans online if you needed them.

This year I added a few bags of compost/manure and mixed it in well.

    Bookmark   May 6, 2010 at 1:36PM
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jnfr(z5b CO)

I tried a 12" deep bed to start but lowered it to 6" when I rebuilt them. My garden gets full southern sun and has total wind exposure, and the deeper beds (which were also thinner wood) dried out really, really fast. Since moving to shallower beds with thicker wood, the soil stays a bit moister and cooler in the middle of summer, which in my situation is a plus.

    Bookmark   May 8, 2010 at 10:00AM
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I am a devotee of cinder blocks for raised beds, which makes mine 16" high. It's a nice height to sit on while working. I do not remove sod, but smother with newspaper and then lasagna the bed. It's very easy and gives excellent results. I think cinder blocks + lasagna method + mulch galore makes the easiest way to grow vegetables and gives good results.

I have read that many veggies have tiny root systems that extend further than you would think, so deeper is better.

    Bookmark   May 14, 2010 at 1:05PM
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redley_gardener(5 - Golden CO)

Autodidact did a similar thing that I did.
I made my 4x4 beds 8" high and my 6x4 beds 12" high.

Look into lasagna gardening.
Soak a large section of newspaper, spread it out over the grass. Then layer green and brown. You will get wonderful wet soil and have earth worms galore. I layered mine like this: newspaper on the bottom, then seasoned cow manure, leaves, seasoned cow manure, leaves. The top layer, I mixed seasoned 1/3 cow manure with 1/3 vermiculite and 1/3 peat moss. This is a bit out of square foot gardening. I didn't have compost or I would have used that instead of the seasoned manure.

    Bookmark   May 15, 2010 at 4:45PM
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