raised-bed Raised Bed or 100 to 150 gallon Root Pouches as Raised Beds

What I've grown in containers this year has done OK, but it seems like it would be easier to have a single raised bed set up on an automated watering system. I have room on the east side of the house in the back yard to build and maintain a 6' x 24' bed. It would be on a concrete slab. Sun exposure would be from mid morning to mid afternoon. And yes, I am aware that once built and filled, there would be no way to move it!

I've not done anything like this before so I have a few questions:

The first is the depth. I was thinking about 2' tall, and filling it to about 1.5' in soil. Deeper? Shallower? Just right?

The second question is the soil itself. Should I use something light like a potting mix, denser like garden soil, or a combination of the two?

The third question is do I need drainage holes in the bottom? If so, about 1" diameter every square foot? Less? More? None?

The third is plant spacing. I was thinking roughly two feet between each plant. This should allow for about 36 plants (3 rows of 12 plants). At 6' wide, I would still have access to the center row from either side of the bed for pruning, harvesting, etc.

Any answers would be very helpful to me and certainly would help me decide if it is worth the effort to construct this thing for next year.

Thanks!
 
What type of bed are you building (ie. cement blocks, wood) -- Is the slab already in place ? -- Is it up against your building or is there going to be space to walk between the bed and the building ? Does the cement slab have any incline for drainage so that the water drains in one direction - would it hurt anything if the water drains around the garden on all sides ? Figure if you are placing it directly on the slab without sealing the edges and are not worrried about how it drains (ie. the garden is not directly against your building) then there shouldn't be a problem with drainage - I would place a couple inches of rock for the bottom of the bed so water drains from the soil into the rock and it will drain around the bed fine if it is not sealed to the concrete.

Figure you'll want 2 or 3 inches of gravel for the bottom and then about 18 inches of soil if building it 2 ft. tall that should work out fine leaving 2 or 3 inches inches from the top. For filling probably some good top soil (garden soil) and compost should be a good start -- figure 24x6x1.5 ft would be 8 cubic yards of soil ( 1 cubic yard = 27 cubic ft.) - so I'd probably use 6 yards top soil and 2 yards of compost (maybe mix in some good slow release balanced fertilizer (ie. Ozmocote or similar) and about 1 to 1.5 yards of gravel ( 24x6x0.25 (3 inches = .25ft.) = 1.33 yards) in the bottom for drainage ( perhaps place the gravel in the bottom cover with landscape fabric then with the soil and compost mixture to keep the soil from compacting down into the gravel.

For spacing I'd probably go 2 rows 18 inches between plants in the row instead of 3 rows @ 2ft. ( same number of plants ) and put each row about 1 - 1.5 foot in from the edge of the garden -- that way you have 18 inches of root space on each side between rows and 9 inches between plants in the row for each plant so they are not competing for space while small yet still get good sun from all sides vs. having a center row that is blocked on all sides.
 
I just built a small bed, 5 foot by 11 foot, it is 18 inches deep. Took nine bags of miracle gro garden soil, 2 cubic foot bags, 8 bags soil conditioner, 2 cubic foot bags, 2 bags of manure compost, i 1 cubic foot bag, and 3 bags of hardwwod mulch, 1 cubic foot bags, to fill it. Dug up the grass on the bottom then used an weed preventing mat on the bottom.

I feel my plants, with such a long growing season are limited by even a 5 gallon container.
 
I just built a small bed, 5 foot by 11 foot, it is 18 inches deep. Took nine bags of miracle gro garden soil, 2 cubic foot bags, 8 bags soil conditioner, 2 cubic foot bags, 2 bags of manure compost, i 1 cubic foot bag, and 3 bags of hardwwod mulch, 1 cubic foot bags, to fill it. Dug up the grass on the bottom then used an weed preventing mat on the bottom.

I feel my plants, with such a long growing season are limited by even a 5 gallon container.

Good to know. I agree about containers limiting potential, especially when I see the results of in-ground planting compared to pots. In-ground is not an option for me, but this would be. Good luck with yours!

What type of bed are you building (ie. cement blocks, wood) -- Is the slab already in place ? -- Is it up against your building or is there going to be space to walk between the bed and the building ? Does the cement slab have any incline for drainage so that the water drains in one direction - would it hurt anything if the water drains around the garden on all sides ? Figure if you are placing it directly on the slab without sealing the edges and are not worrried about how it drains (ie. the garden is not directly against your building) then there shouldn't be a problem with drainage - I would place a couple inches of rock for the bottom of the bed so water drains from the soil into the rock and it will drain around the bed fine if it is not sealed to the concrete.

Figure you'll want 2 or 3 inches of gravel for the bottom and then about 18 inches of soil if building it 2 ft. tall that should work out fine leaving 2 or 3 inches inches from the top. For filling probably some good top soil (garden soil) and compost should be a good start -- figure 24x6x1.5 ft would be 8 cubic yards of soil ( 1 cubic yard = 27 cubic ft.) - so I'd probably use 6 yards top soil and 2 yards of compost (maybe mix in some good slow release balanced fertilizer (ie. Ozmocote or similar) and about 1 to 1.5 yards of gravel ( 24x6x0.25 (3 inches = .25ft.) = 1.33 yards) in the bottom for drainage ( perhaps place the gravel in the bottom cover with landscape fabric then with the soil and compost mixture to keep the soil from compacting down into the gravel.

For spacing I'd probably go 2 rows 18 inches between plants in the row instead of 3 rows @ 2ft. ( same number of plants ) and put each row about 1 - 1.5 foot in from the edge of the garden -- that way you have 18 inches of root space on each side between rows and 9 inches between plants in the row for each plant so they are not competing for space while small yet still get good sun from all sides vs. having a center row that is blocked on all sides.

Thanks for the detailed reply. I had planned to make this from wood. The slab is level and already there. The bed would be three feet away from the house, and no side would be against anything. If it drains onto the concrete, nothing bad will happen. No worse than if it rained on it right now. I had not planned on sealing it to the slab.

Good point about the gravel/rocks for the bottom. I hadn't thought about that and it makes perfect sense. I do plan on having a bottom to the bed, so should I drill drainage holes? If for whatever reason we got a serious rain (which occasionally but not often happens), then the plants wouldn't be swimming.

Your idea about spacing also seems sound.

On to soil. So we really are talking garden soil as opposed to potting mix? Would it be beneficial to have a mix of the two, so that the growth medium is somewhat more porous than soil but a bit more dense than a container? Might be less prone to compacting? I ask because, before I started thinking of this, I was planning my grow for next year assuming I'd be using containers. I've already got two 3.8 cubic foot bags of Sunshine Mix #1, two more of Sunshine Mix #4, and some amendments like Ancient Forest, worm castings, bat guano, and kelp meal. So that's maybe 16 cubic feet total. I could mix that with 11 cubic feet of some sort of "garden soil" to come up to 27 and probably have a pretty fertile medium. If I went down this path using what I already have, what would you recommend I use to complete the remaining 11 cubic feet?
 
Placing a wooden frame to the slab should still allow plenty of drainage without having to drill drainage holes and with some gravel at the bottom for the water to drain into it should be fine without any special setup for draining.

On the soil for the size you are talking -- 6 foot x 24 foot x 2 foot. your actually talking 288 cubic feet !! but figure of that space your gonna use say 3 inches of gravel or 36 cubic foot of gravel (1.33 yards) and you'll want to leave about 3 inches of space on top (another 36 cubic feet) leaving you needing 216 cubic feet of soil (8 yards) -- So quite a bit of soil.

So I'd check with a local nursery and see what they charge per yard of topsoil and compost ( here they want about $25 -$30 per yard of compost and $15 - $20 for topsoil - where potting mix soil in bulk runs around $60 - $100 a yard (still cheaper than 14 - 2 cu ft bags at the hardware store but pretty steep for growing 30 - 40 pepper plants ! ) which is much more cost effective than trying to use bagged soil - so so I'd check in the local area and see what you can find (also may want to check the quality of it as well since it can vary from supplier to supplier. )

Also since you have some time check your local area and you might find a free source for compost - if there is a local dairy farm they may have some decent compost they'll give you
 
Whoops! My bad on the math! I just saw the 27 cu ft and ran with it. Upon closer reading that was 1 cu yd = 27 cu ft! So let's see, I have just over half of a cubic yard, hahaha! 7 1/2 to go.

Well, at this point it is still just an idea. I've done nothing yet to commit. Plenty of time left to ponder this and, if I ultimately decide to do it, make it happen before time to put sprouts/overwinters outdoors.
 
I was just doing a bit more math regarding this project. Would it be OK to have the bed be only one foot tall? If it was 12" tall and 9" of that was soil, for 36 plants there would be 3 cubic feet of soil per plant, which comes out to about 22 gallons! It would also (obviously) take half the soil: 108 cubic feet (excluding the rock in the bottom). With 2 inches of rock in the bottom, there would be 7" of soil, which still comes out to a bit over 17 gallons per plant. 84 cubic feet of soil would then be needed, just over 3 cubic yards.

Any reason why this wouldn't work?
 
Should work fine -- another thing you could do is still make the depth 2 foot and just leave more space at the top unfilled the first year (buy what you can afford and fill what length you can to the depth you want (and if needed just put a divider in place to hold the soil in place where needed) and then add additional compost and\or soil the next season - Or do a 12 foot garden this year and build a second one next year - Or do one 2 foot wide x 24 foot length box this year and add a second on the opposite side of the slab next year and attach them together and fill the middle the third year -etc. That way you spread the cost out over a few years and still get what you wanted in the end. There's really no wrong way to do it - just figure out the cost of the various options and go with the one you can afford - The good thing is you can always add on in future years !
 
I wouldn't bother with gravel at the bottom. Unless you place filter fabric between the rock and soil the water will cause fine soil particles to migrate into the airpsace between the rocks and eventually it won't drain as well as if you had just used all soil.

My beds are about 2' deep and were filled with bulk delivered planting mix from my local landsape material supplier. The level of the soil drops about 2" after a growing season due to the breakdown of organic mater. I top off the beds with fresh compost before I plant and don't even bother to mix it in but it needs to be well composted stuff not fresh manure.

As to size 4' wide is what I find comfortable to easily reach from both sides with 2 rows of plants running the length.
 
I wouldn't bother with gravel at the bottom. Unless you place filter fabric between the rock and soil the water will cause fine soil particles to migrate into the airpsace between the rocks and eventually it won't drain as well as if you had just used all soil.

My beds are about 2' deep and were filled with bulk delivered planting mix from my local landsape material supplier. The level of the soil drops about 2" after a growing season due to the breakdown of organic mater. I top off the beds with fresh compost before I plant and don't even bother to mix it in but it needs to be well composted stuff not fresh manure.

As to size 4' wide is what I find comfortable to easily reach from both sides with 2 rows of plants running the length.

Thanks for your input, as well. Hmmm, 4' wide. That would take even less soil and would still be at least 14 gallons per plant...and easier to tend. This project is sounding more doable with every post!
 
Another thought: Root Pouches. These seem pretty cool and if I'm reading correctly, pretty inexpensive. The layout of my yard (unused area) would easily accommodate ten 100 or 150 gallon Root Pouches. http://rootpouch.com/prices. $31 for a 150 gallon pouch is not that pricey.

The 100 gallon pouches have a diameter of 38" and the 150 gallon ones a diameter of 45". I was thinking of 4 plants per pouch, which would be 40 plants total. Does anyone think the 100 gallon pouches would be too small for four plants? I'm thinking the 150 might be better. If the plants were planted about 10" from the side, there would be about 18" between each plant.

At 22" deep (150 gal), they could be filled to about 16 to 18", so they would be more like 115 gallons each. This would take about 5.7 yards for all 10. At a 12" fill, probably still deep enough, they would be about 82 gallons each, and require about 4 cubic yards of soil total.

This would be much easier than building a raised bed, should still give the benefits of in-ground, but the plants would be somewhat separate. If a soil bug hit one pouch, it shouldn't spread to the plants in the other pouches as might happen if all plants were in a single bed.
 
I've wanted to do this as well, but at the same time if I would have had it this year I would have lost my plants twice now to hail. :/
 
Id be putting some drainage pipes down on the concrete slab myself, these are a nice option (flat) and they have a sock that goes over the top.

Megafl_1_310x235_f.jpg


Mezo.
 
Id be putting some drainage pipes down on the concrete slab myself, these are a nice option (flat) and they have a sock that goes over the top.

Megafl_1_310x235_f.jpg


Mezo.

Pretty high-tech there, Mezo. ;) Actually pretty cool.

Anyone have any thoughts about the 100 or 150 gallon Root Pouches as raised beds? Smallest one for four plants? Still undecided on this or individual 5 gallon Root Pouches.

On a side note, has anyone put worms in their raised beds? Seems like they might help aerate the soil and provide nutrients in their castings.
 
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