Raised Planting Beds

[daveswoodhauler]

Well, I got done with my wifes 15 X 30 Garden, and now she would like a few raised beds for additional plants. (I would like a few as well, as I wanted to start a herb garden, and like the idea of not bending over as much)
Is there a rule of thumb on how deep they should be?
I have some left over decking that it perhaps 5-6" high when on its end, would this be deep enough? (I will be able to dig perhaps 4-6 inches of soil below the raised bed, but after that its very rocky/ledge) I guess in total, we will have about 12 inches of soil in depth....maybe just stick to small plants?

 

[muncybob]

My raised beds started out at only 5" or so deep but have gotten deeper each year with additional ammendments(mushroom soil, compost, etc). I'm now getting to the point of maybe increase the height of my borders. Raised beds have some advantages to them so I say why not! Is the decking you plan to use pressure treated?? Many feel you should not use PT lumber in an area of edible plants.

 

[daveswoodhauler]

Thanks Bob. Yes, the boards I have are PT, so that was one of my concerns....the PT lumber was purchased only about a year ago, so I have heard that the chemicals used in the newer stuff is not as bad as the older PT stock....but I don't know too much about this.
Perhaps I can find decent lumber that is rot/moisture resistant....kinda on a small budget and was trying to use stuff that I currently have on hand.
Thanks for the help

 

[Slow1]

I'm also in the process of building new beds... last ones got buried when we did the addition on the house. However when we did those we used 2x8's on edge and rocks (plenty of those around here) outside to help keep them in place and make it look a bit nicer. These were untreated and although they did start to rot a bit, they were still working very well 3 years after first install. In that case I had dug down quite a bit to prepare the space...

My new location the ground under these beds is terrible - I can't see planning on getting anything out of digging into the ground and roots won't likely be able to penetrate that ground for a year or two I imagine. So to the OP's original question.. Does anyone have a guideline of how deep a garden should be (minimum) for decent plant growth? Is there a guideline of some sort somewhere? If I were putting this bed on concrete for example, how high would I need to build the walls and fill in to expect an ok crop of tomatoes, peppers, lettuce, carrots, etc?

 

[goldfishcastle]

according the the square foot garden method that was started in the 70's and continues today - 6" is all you need. we're just starting this year as well. but last year in the community garden we had great harvests and growth with the 6" of good soil and doing nothing to the soil underneath.

i really wouldn't use treated wood. the chemicals will leach in the soil stunting growth and making the food toxic. i think it would be worth the extra expense to purchase the wood. another idea - make smaller beds (say 4'x4') and use construction pieces.

 

[StackedLumber]

Thanks Bob. Yes, the boards I have are PT, so that was one of my concerns....the PT lumber was purchased only about a year ago, so I have heard that the chemicals used in the newer stuff is not as bad as the older PT stock....but I don't know too much about this.
Perhaps I can find decent lumber that is rot/moisture resistant....kinda on a small budget and was trying to use stuff that I currently have on hand.
Thanks for the help

Dave,

Everything I have heard is that the new PT stuff is way worse than the old stuff. When we built a deck a two yrs ago we had to get a new special coated screw b/c the new copper treatment in the PT wood will destroy the old type of screws. I'd be concerned w/ it leaching into your soil. We've used simple concrete landscaping blocks or you can also use natural cedar 4x6's as a way to raise your beds. There are also landscaping timbers you can buy that aren't treated. One thing that lots of people do here is use just common rocks to build a raised bed.

Just my thoughts.

 

[StackedLumber]

I'm also in the process of building new beds... last ones got buried when we did the addition on the house. However when we did those we used 2x8's on edge and rocks (plenty of those around here) outside to help keep them in place and make it look a bit nicer. These were untreated and although they did start to rot a bit, they were still working very well 3 years after first install. In that case I had dug down quite a bit to prepare the space...

My new location the ground under these beds is terrible - I can't see planning on getting anything out of digging into the ground and roots won't likely be able to penetrate that ground for a year or two I imagine. So to the OP's original question.. Does anyone have a guideline of how deep a garden should be (minimum) for decent plant growth? Is there a guideline of some sort somewhere? If I were putting this bed on concrete for example, how high would I need to build the walls and fill in to expect an ok crop of tomatoes, peppers, lettuce, carrots, etc?

Most plants don't go much deeper than 4 inches. 2 inches of cheap fill dirt and 4 inches of good soil, manure, peat, sand mixture will grow you all that you need.

 

[btuser]

The new pressure treated wood is better than the old stuff. New stuff=copper. Old stuff= arsenic. Catch 22 being plants are very sensitive to copper, especially aquatic plants. You'd have to grow your plants in mulch made from the pressure treated sawdust to have an issue of it getting into your washed veggies, even the older PT had a VERY HARD TIME contributing to the arsenic level in edible plants. This problem is way overblown.

That being said when I built my raised bed garden I used pine and resigned myself to having to rebuild every 5-10 years. Why? Because my wife read something somewhere and I don't want questions about what side of a fence/board this particular cucumber or tomato was raised.

 

[PapaDave]

If you have any mills nearby, yoou could get some slabs and use that. Around here, you can get almost a cord of slab wood for about 20-30 bucks. Make as many raised beds as you want with all that.
We're also doing raised beds this year (if I can ever get to finish them), but mine will be quite high. Looking to go about 32", and we'll fill with leaves, saw chips, basically anything that will decompose over time. Compost will go on top. Might get a couple yards of topsoil too. Gotta' call the local guy for a price.

 

[btuser]

The new pressure treated wood is better than the old stuff. New stuff=copper. Old stuff= arsenic. Catch 22 being plants are very sensitive to copper, especially aquatic plants. You'd have to grow your plants in mulch made from the pressure treated sawdust to have an issue of it getting into your washed veggies, even the older PT had a VERY HARD TIME contributing to the arsenic level in edible plants. Ask yourself if you plan to test your soil and water for natural arsenic/copper levels, because that is by far the major contributing factor. This problem is way overblown.

That being said when I built my raised bed garden I used pine and resigned myself to having to rebuild every 5-10 years. Why? Because my wife read something somewhere and I don't want questions about what side of a fence/board this particular cucumber or tomato was raised.

 

[daveswoodhauler]

So, if I go pine/spruce, how many years do you think I would get out of them? (I'm thinking 2 X 8"s or 2 X 10"s)

 

[daveswoodhauler]

If you have any mills nearby, yoou could get some slabs and use that. Around here, you can get almost a cord of slab wood for about 20-30 bucks. Make as many raised beds as you want with all that.
We're also doing raised beds this year (if I can ever get to finish them), but mine will be quite high. Looking to go about 32", and we'll fill with leaves, saw chips, basically anything that will decompose over time. Compost will go on top. Might get a couple yards of topsoil too. Gotta' call the local guy for a price.

Kinda a dummy when is comes to slab wood. Is slab wood, basically, the outercut/strip with some bark on it that the mills can't use?
If it is, I kinda like this appproach, as it would be economical, and using a product that would probably be just turned into mulch or something?

 

[PapaDave]

If you have any mills nearby, yoou could get some slabs and use that. Around here, you can get almost a cord of slab wood for about 20-30 bucks. Make as many raised beds as you want with all that.
We're also doing raised beds this year (if I can ever get to finish them), but mine will be quite high. Looking to go about 32", and we'll fill with leaves, saw chips, basically anything that will decompose over time. Compost will go on top. Might get a couple yards of topsoil too. Gotta' call the local guy for a price.

Kinda a dummy when is comes to slab wood. Is slab wood, basically, the outercut/strip with some bark on it that the mills can't use?
If it is, I kinda like this appproach, as it would be economical, and using a product that would probably be just turned into mulch or something?

Yep. You can use a drawknife or spokeshave to debark (maybe someone else has a better solution), but the bark should be taken off. Quite a few slabs that you will get in a load will actually look like boards. Pretty rough , but still boards.
One of our friends uses slabs for all kinds of lean-to's, small bunny hutches, siding, etc.

 

[woodsman23]

I used mill cut lumber lartch pine and then coated it with some deck stain (water based) and allowed to dry then used it and it has been well over 5 years and counting. Amish here have lartch pine cut to 2" x 10" x 12 for 6 bucks each...

 

[steviep]

I made mine 4'x16' out of 2x10 non pt lumber that I had laying around . I actually made it just under 4x16 so that when it rots out I can just install 4x12 rough cut around it.

 

[timfromohio]

I'd go deeper than 5" or 6". I have been growing in raised beds for about 8 years now. I built them out of dimensional PT lumber, but lined the ones that have food plants in them with plastic so that there is no contact between the wood and the soil. I used 2x6 lumber and stacked used 2 levels to get to 12" in height (well not quite b/c it's dimensional lumber, but you get the idea). The deeper the bed, the closer you can plant things and you'll want deeper than 5" anyway if you want to grow carrots or deep-rooting plants like broccoli (spelling?).

If you take a look at the "10 acres is enough" thread from a while back I posted some picks of the our raised bed garden area. I find them excellent for things like peppers, tomatoes, herbs, lettuce, beans, and cukes but have gone to traditional rows for things like corn and squash.

Remember, there's also always buckets - I'm trying a bunch of potatos in buckets this year for the first time.

Also, HD had their composite decking material on sale - I would have used that stuff in the first place, but at the time it was too expensive. Regarding bed dimensions, don't go wider than about 4' - it gets hard to reach across. And remember, the longer the lumber the more likely it is to have bows and cracks. I stuck to building either 3'x5' or 4'x8' beds.

Post pics when you're done and let us know how the garden goes! Good luck.

 

[daveswoodhauler]

Thanks Tim. I was thinking 4 X 8 as I was telling my wife that any wider and youwould not be able to rach to the middle of the bed. We have a scratch and dent sort of store here a few towns over, so maybe I can find some of the comp decking there on the cheap side. Actually, I was thinking about making the north end of the beds a little higher than the south end, and was goin gto also use them as a cold frame for early planting.....I always see adds on craigslist for old storm windows and such, so I think I might make the baeds about as wide as I can find some old storm windows to use. Thanks for your thoughts

 

[begreen]

I'm also in the process of building new beds... last ones got buried when we did the addition on the house. However when we did those we used 2x8's on edge and rocks (plenty of those around here) outside to help keep them in place and make it look a bit nicer. These were untreated and although they did start to rot a bit, they were still working very well 3 years after first install. In that case I had dug down quite a bit to prepare the space...

My new location the ground under these beds is terrible - I can't see planning on getting anything out of digging into the ground and roots won't likely be able to penetrate that ground for a year or two I imagine. So to the OP's original question.. Does anyone have a guideline of how deep a garden should be (minimum) for decent plant growth? Is there a guideline of some sort somewhere? If I were putting this bed on concrete for example, how high would I need to build the walls and fill in to expect an ok crop of tomatoes, peppers, lettuce, carrots, etc?

Most plants don't go much deeper than 4 inches. 2 inches of cheap fill dirt and 4 inches of good soil, manure, peat, sand mixture will grow you all that you need.

Though that may be true for some flowering annuals, many plants go deeper than 4". It depends on the plant. We've had several plants fill a 12" pot with roots after a year. Perennials can have very deep roots. Root crops like carrots also like much deeper soil. Our raised beds run from 9" to 15" deep.

 

[kenny chaos]

My observations on raised beds have shown there are more empty ones than full ones.

 

[daveswoodhauler]

Well, if it stays empty my kids can use it for a sand/dirt box with their tonkas

 

[timfromohio]

The cold frame idea is a good one - you could just put some straw bales around the bed and lay an old storm door over the top - done. The raised bed also creates an easy platform onto which you can attach other stuff. For example, we have three beds that we use exclusively for strawberries - I have small 1x1's attached around the perimeter of these beds. On top of these I place old pasta sauce glass jars and then stretch netting over them (you can imagine the netting getting caught on wooden stakes or poles - the glass jars create a nice large surface area that the netting can rest on, large enough that it won't fit through the netting) and then staple down the netting around the beds. Works great. Also very easy to attach sections of pvc pipe on the sides to create a frame for row covers. I've also thought of making some frames around which I can attach some plastic - put them down and the soil will warm up significantly faster. For many plants raised beds are awesome.

 

[BucksCoBernie]

I plant in raised beds made from untreated pallet boards (surprise!). I didnt bother weatherproofing mine and they are still holding up. when its time to replace them I'll just get more free pallets. What you could do is treat your pine boards with linseed oil and melted bees wax to waterproof them. no nasty chemicals in the soil this way.

 

[Mainely Saws]

I built mine out of the standard 3" x 5" x 8' PT landscape ties . I built them 4' x8' x 18" high . It gives you easy access from all sides & I like the height because you don't have to bend over so much & it makes a nice place to sit once in a while . I have made other similar beds up against the house foundation but only about 3' deep instead of 4' .........
The next time I'm going to spring for the extra dollars & build them out of landscape blocks so it's an over & done deal , right now the PT ties last about 6 to 8 years before they need replacing ........

 

[JBinKC]

I wouldn't want them much wider for harvesting purposes. My raised beds are 4'x8'x 8" that I cover with a permeable fabric to prevent weeds and retain water.

 

[begreen]

This year we are trying a grand experiment. Our raised beds are 15" deep with no connection to the soil beneath them They are on top of commercial, nursery landscape fabric and they are made out of poured cement forms. We have 10 - 4' x 14' x 15" deep beds, 2 - 10' x 4' x 15" beds and a few 9" deep beds for herbs, strawberries and flowers. How well it will all work out is still unknown. We expect a year or two to be learning. Late winter, we had record setting warmth for Feb and Mar and now the weather has flip-flopped and we are running a steady 10°F below average. Stove has been burning 24/7 for the past week. Will post updates as the season progresses.