How deep should raised beds be?

[yippee]

Hello all. I am looking to revamp my garden some this year. I have been doing a container garden for many years out of 5 gallon buckets with good success. However many of my buckets are brittle from sun damage and starting to fall apart, so I was considering starting to convert over to raised beds instead. I am planning to price some options out tomorrow to decide what will be best. I am considering building one from cedar lumber or possibly a galvanized stock tank. Since I would be building with the lumber, I could essentially make them whatever height I wanted them to be. On the stock tanks they look to come in 12" or 24" heights. Just from quickly looking into it, I find a lot of people saying 12" is good for a raised bed. Then I see some people say tomatoes need more like 24" for their root systems while other people say 24" is too deep and you would need to fill some space with empty milk jugs or something similar to kill some of the space to save from having to fill it all with soil. I was just wanting to get some info from you fine folks to get a better idea on what I should be looking for. I normally do a couple of tomato plants, some various pepper plants, a cucumber plant, zucchini, squash, okra plant, and possibly something else if I am overlooking anything. Do y'all think a 12" would work well for those or is the 24" really where I need to be looking?

Thank you.

 

[Acre4Me]

Where are you located? General info bc it helps understand your weather. It is a Garden thread, after all, so we are interested!

We have 11 raised beds for a total of approx 600sq ft of planting. Then we have a large 20'x30' bed for another approx 600 sq ft of garden space.

Raised beds: these are great! We have 12" tall beds. They sit on top of the dirt, so plants can go deeper if they want. We spread out mulch around the beds to keep down weeds, and to walk on mulch instead of dirt. When we had grass around the beds, it was weed city. We have talked about making taller beds, but need more soil, and that is costly, and then the supplies to make the beds taller. Maybe as we age, we will decide to have some taller beds for ease of gardening, but for now these current ones are good.

Why we chose raised beds: gives a defined area. Attractive, keeps plants and bugs separate. When it rains heavily or for a prolonged period, it can overwhelm the area for a short period of time - so plants stay out of any water. But, since we raised up the ground a small amount, this happens less.

Soil: the limiting factor bc it can be costly - especially if you buy good soil. We bought a truckload (50 tons?) for the 20x30 bed. To keep costs manageable, we bought "good" but not "great" soil as we could amend it. We've gotten soil testing done and are slowly optimizing it. I expect it to take another 2 years to get it to a much better point. So, I have to spend $ to improve the soil, but you have to add/improve any soil anyway. We have a compost bin, and should get first completed batch this year. We also amend with gypsum (for calcium), Sulfur (bc our soil is more basic and we need to lower the pH), green manure - a living cover crop like buckwheat or peas, etc that gets turned under to rot, balanced granular fertilizer, peat moss (adds a bit of acidity), perlite and vermiculite (both help with water retention).


We evened out the area for the garden. We bought 102 tons of fill dirt and had it spread around. The area had some various low spots/ The 102 tons of dirt came in 4 truck loads. It was not great dirt as it is fill dirt, but not terrible, and not too rocky - any rocks were of a certain size or smaller - none very big.

5th truckload of "good" garden dirt for 20x30 bed.

Building beds on a sunny winter day.

Filling beds with dirt. We had moved all previous garden bed dirt to make room for the leveling out process, and then carted it back into beds. We built more beds, so had to source more dirt. Here we are adding sand to the beds, as we were still battling heavy clay. Who puts heavy clay soil into raised beds? The previous owners, that's who.

in the foreground is the 20x30 bed, then many of the raised beds. There are 2 more in the sunniest SE corner of the yard, that are not in any pics. Chicken coop and run is on left side of pic.

Yay for green plants!

Use beds to grow Up, Up, Up! Pole beans

Another perspective. Bean tower that is moveable and 10' tall (but 7 or 8' is a great height), and cattle panels to the right of bean tower for cucumbers and vining squash. potatoes are in the foreground.

And lets not forget to shade the chickens with plants - it is after all another place to get some growing in. But, they will reach through and eat whatever they can reach, so keep that in mind.

Don't want to use an area? Just cover with plastic. If in hot weather, it will help to kill any bugs that are in their larval or grub stages bc it will heat up the soil. also helpful to kill weed seeds. I've covered in plastic during July, after a spring crop, so when I plant for fall stuff in later July, I have fewer pest and weed problems.

And we built a traditional compost bin since we have a lot of amending to do. Left side is new additions. Middle is partially complete. Right is going to be for finished.

Seems like a lot, but all this is crammed into a fairly small area at the back of our not-quite-an-acre lot, and most of it cannot be seen from the road!

 

[Percheron chick]

I'm in the same boat as you. I however just finished my first phase of raised beds. Plants do require different depths for optimal root growth. Some of that can be enhanced by extending their root system down beyond the framework of the bed by breaking down the sod you plant on top of. Building beds of varying heights can add visually to the garden and save on costs but it will limit your options when you rotate your beds. Start with one 8x4 bed 22" tall. That works out to 9 2x8x8. You will also need 2 2x4x8 for corners and bracing. I went with pine and one bed cost $75. I painted and lined the box to help extend it's life. One bed requires the better part of one pickup truck load of dirt. I like the look of the stock tank beds and always have old leaky ones around but they don't work for me. They overheat in my 90*+ summers and require daily watering. Tomatoes just have been stressed and under preformers in stock tanks. Flowers do best.
Instead of using plastic or foam to help fill the box, use organic material that will break down over time. Cardboard, shredded paper, unfinished compost, horse poop, leaves, hay... Money in the bank. As it breaks down in the years to come, it will replenish the soil. Fill the top half with a good growing medium.
If you go with stock tanks, first check out CL for free leaky ones. You will need to drill holes in the bottom for drainage and it's a crime to take a perfectly good ,$100 tank and ruin it. Another advantage of going taller on the beds is it will help keep rabbits and geese out. Also do some research on vertical gardening for the cukes and squash. It will control the vines taking over the box and choking out the rest of the garden.
One 8' bed will limit how much you can grow as your wish list far exceeds the space you have available. I went with 3 8x4 and one 12x4 beds and am already considering adding one more 8'. You can save money on your beds by using lumber 2nds. HD and Lowe's both sell warped and damaged lumber. If you have a local Restore (recycling used construction materials) those can be hit or miss and for the cost of removing a few bent nails, there is always dumpster diving.

 

[Sally PB]

Wow, after seeing what everyone else has done, I feel a little silly talking about my raised beds.

I marked out where I wanted the beds. I took the topsoil from the space between them and put it on top of the soil that was there. (This was already a garden, not sod, btw.) I did this in the fall and put all the compost I had on top of the piles. My husband mowed the fall leaves into mulch, and I piled that on and worked it in with my hands. I got in touch with my inner child and pretended I was making mud pies.

I mulched the walkways between the beds HEAVILY with raked up thatch the next spring. My garden production was about the same as it had been before the raised beds, but it was much easier to work in. (Much much easier.) It was also not a very good year for gardens in the area, so I felt like the beds had done better.

Each year, I mulch the walkways with thatch; straw would work too. In the fall, I rake it up and put it on the raised beds. I add compost as often as I have it, and I have a lot more now that I have chickens.

Each spring, I "neaten" the sides of the beds, as they do tend to settle and spread. I am slowly bolstering the sides with rocks, which I have for the labor of moving them. I like the look of the beds, the garden is neater, and I can move around and work in there more easily.

I'd say my beds are about 12" high from the surrounding soil. The roots can go as deep as they like.

 

[BReeder!]

Thanks for the mention @Acre4Me.

First my opinion is a raised bed can be as deep as you want it. Just a 2x4 on its side is fine for some, and in my case a 26" galvanized steel panel is fine for me.
Deeper beds dry faster at the top which is good for pants that don't like their roots wet but bad for those that do. Deeper beds offer the benefit of needing to bend over a little less. You could even build seats onto the outside of deep raised beds. Shallow beds require you to get down lower. My deep beds will never be trampled on by the kids or dog because of their height, which is also a hurdle for some animals such as rabbits - not that they cannot get into them but I had far more success with lettuce in a 2ft deep bed than a 1ft deep bed where it was decimated by rabbits.

I grow in deep needs and some shallow beds as well as right in the ground. The deep beds are my favorite though. Directly in the ground is reserved for large and tall plantings like potatoes, tomatoes, corn, squash and pumpkin.

Now for a pic. This is from the Fall when most things were already harvested and clean up was under way.

Just to add to my love of these, I'm replacing the two to thr left of the pic (1 in front and 1 in back) with galvanized steel beds to match the others. I will repurpose the 2x12 lumber in those two old beds to make two new raised beds to hold a strawberry patch and herbs. Those will still be 1ft tall, but protected with wire.

 

[CluckerFamily]

I had lots of cardboard so I laid cardboard onto the grass to kill it, on top of the cardboard I placed my raised beds with soil. My raised beds are 6” deep but the plants can root into the land’s soil.

 

[rosemarythyme]

I'm in between your two measurement at 16", with cedar beds. I would love 24" to really minimize bending down (which is a primary reason I have raised beds in the first place) but 16" isn't too bad. I find that adequate for tomatoes and squash, plus it's tall enough to keep wild rabbits out of my greens.

If you're going to go deep then you can fill in the bottom with branches, cheaper soil, etc. to help lessen the costs - really no reason to fill an entire bed with expensive soil. I fill about halfway with cheap bagged stuff, then the rest with a good quality locally mixed amended soil, topped with my own compost.

 

[NatJ]

Aggressive vines and grasses can be a real bear. Pull what you can and starve the rest out with black plastic. That's the only way I know to get rid of such things without chemicals.

I'll bet chickens could do the job.

Build a chicken run on the spot, let the chickens reduce it to bare ground, and then continue keeping the chickens there another year or two.

 

[rosemarythyme]

Wow, after seeing what everyone else has done, I feel a little silly talking about my raised beds.

I marked out where I wanted the beds. I took the topsoil from the space between them and put it on top of the soil that was there. (This was already a garden, not sod, btw.) I did this in the fall and put all the compost I had on top of the piles. My husband mowed the fall leaves into mulch, and I piled that on and worked it in with my hands. I got in touch with my inner child and pretended I was making mud pies.

Nothing wrong with doing mounds - I tried that for my shade garden, and also have a large flower bed (not sure what else to call it, random things grow there) that's basically a giant mound next to the driveway. Though I admit I like the look of hard edges so I went back and added them to the shade garden since I had some wood to work with after dismantling a used kit-type garden bed.

 

[Acre4Me]

@BReeder! Has some taller raised beds using galvanized sides - maybe he can add some pics when he gets a chance.