How deep should raised beds be?

[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.

 

[BReeder!]

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.

That's a great point. My beds have local soil in the bottom 1/2-2/3 right from my yard - we had plenty after digging out a 5'x10' pond and doing some landscaping work. I also have added branches, short sections of logs, and garden waste. I have a bed I'm going to top off with dirt this Spring that I filled all last year with garden trimmings, weeds, damaged vegetables (like the tomatoes that squirrels bit), and the vines and stalks we pulled when cleaning up the garden. I'm letting all that break down a bit over winter and into Spring, and will be stomping it down and piling soil right on top of it all in a month or two.

Another note is that beds filled with debris in the bottom do settle a lot. Don't be surprised if a 2ft deep bed only has 1.5ft of soil the next year. Water carries dirt into all the crevices between debris when it rains or snow melts and that causes the soil the drop a bit. Also, soil tends to naturally compact a bit even in beds that's are filled with nothing but soil. I take advantage of the extra headroom in the beds to add compost and a top dress of fresh soil in the beds that drop a lot.

Until a deep raised bed is established for a few years, I would try to avoid planting perennial crops in it. Shallower raised beds have less of a soil drop than the deep beds. All that said though, I'm planting a perennial strawberry bed in a new 1ft deep bed this Spring that I'll be building right before planting time.

 

[Chris2018]

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.

I see this question a lot and the simple answer is, deeper is always better.
If using a stock tank go at least 24 inches if going with a open earth raised bed or a fabric pot then you can get a way with a 18 inches bed.

Of the three tomato types the only tomato type I would grow in a 5 gallon pot or a 12 inch bed would be the Dwarf type tomato. The Determinate and Indeterminate tomatoes need much more space to be "happy", healthy and grow to there full potential.

My tomatoes are grown in 14 and 18 inch deep fabric pots that air prunes the roots but allows the roots to grow freely into the earth below. These fabric pots are also 15 gallon (for Determinate) and 45 gallons (for Indeterminate) or around 2.0 cubic feet and 6.0 cubic feet of soil and I get roots the full with and depth of the pots.

 

[April0617]

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.

I was just wondering to myself earlier today if I could bury the unfinished compost in the bottom of the beds we are making-glad I started reading this thread!

 

[TJAnonymous]

I have many different varieties of raised beds. Some are made from 2x4s or 2x6s, others are made from galvanized roof panels like these -

The roof panels are incredibly economical. They cost $15 at Lowes and 1 sheet gives me a 6' x 2' bed.

I've also used old tires which you can get for free. These do NOT cause any toxic byproduct to your plants because the rubber is inert. (Toxins are only released if you BURN tires.)

Another gardening tip for raised beds.... Fill the bottom half with bulky fillers which eventually break down so you have to use less soil. For example, in some taller or deeper beds, I fill the bottom half with sticks, logs, or even wood chips (get for free from the tree service companies or city waste management). Then fill in with soil in the top half of the bed. Works great for controlling grass and weeds from underneath too....

 

[NatJ]

Another gardening tip for raised beds.... Fill the bottom half with bulky fillers which eventually break down so you have to use less soil. For example, in some taller or deeper beds, I fill the bottom half with sticks, logs, or even wood chips (get for free from the tree service companies or city waste management). Then fill in with soil in the top half of the bed. Works great for controlling grass and weeds from underneath too....

Layers of newspaper, other paper, or cardboard are also good for smothering weeds, and break down in time. So putting some of them underneath the dirt could help block weeds growing up from below, but in a year or two (after the weeds have hopefully died), they would rot away and let the roots of your plants go down into the dirt below.

 

[TJAnonymous]

Layers of newspaper, other paper, or cardboard are also good for smothering weeds, and break down in time. So putting some of them underneath the dirt could help block weeds growing up from below, but in a year or two (after the weeds have hopefully died), they would rot away and let the roots of your plants go down into the dirt below.

Absolutely! I have used newspaper in the past but now I use other materials and save my newspaper for other things. I don't get the paper anymore so I horde whatever I have left. I do use cardboard though.... And other materials, such as the wood chips, used straw or hay that I've pulled out of the barn or coops, leaves, etc.

If I don't need a deep bed, then I recycle my animal feed bags and line the bottoms of my beds with those. That's what I did in the tire pictures I posted before when I planted my strawberries. I also recycle my feed bags to use as a weed barrier in and around my vegetable garden. I just pin it down with landscaping pins. It is much sturdier than landscaping fabric and FREE....lol.

 

[Chris2018]

Layers of newspaper, other paper, or cardboard are also good for smothering weeds, and break down in time. So putting some of them underneath the dirt could help block weeds growing up from below, but in a year or two (after the weeds have hopefully died), they would rot away and let the roots of your plants go down into the dirt below.

To be honest, if your beds are open earth bottoms and more than 12 inches deep there are not too many weed going to make there way out of that much soil.

Also most paper and cardboard have a good amount of chemicals in them.

 

[TJAnonymous]

To be honest, if your beds are open earth bottoms and more than 12 inches deep there are not too many weed going to make there way out of that much soil.

Also most paper and cardboard have a good amount of chemicals in them.

Oh, you'd be surprised... I have some type of thorny vine from hell that is quite aggressive. It has come up through a 3 ft bed that was loaded with wood chips. I eventually just moved the whole dang bed and gave up.

 

[BReeder!]

I was just wondering to myself earlier today if I could bury the unfinished compost in the bottom of the beds we are making-glad I started reading this thread!

I wouldn't put unfinished compost in the bottom of a bed. I would let it finish for a month or two and use it as a mulch and fertilizer. It will likely be ready just as your plants are tall enough to get a thick layer of mulch to suppress weeds and retain moisture in the soil around their roots. Water will carry nutrients from the compost down into the soil for the plants' roots to feed absorb too.