"Should I be concerned about the pressure on this fence from the soil in the bed? "

No significant sideways force at all. There's not much more static soil than garden soil full of roots.

"planning on filling up part of the bed with landscaping rock that I removed from the spot. I'm thinking this will be good for drainage and it means I won't need to purchase as much soil. What can I use in-between the rocks and the soil to keep the soil from going down into the rocks but still allow it to drain properly? "

Again, not an issue for two separate possible reasons. One, you won't need any significant drainage as the unamended dirt under the garden soil will do the job. You are in a wickedly arid environment. Two, the gravel will take up room that could be given over to the growing soil. If your intent is to fill up the entire two feet of depth right away, that also is not necessary. Put in as much garden soil as you can, a foot ain't bad to start, and then fill it up further over the coming years as you get around to it. There will be all sorts of things that can go into that space.

I have the absolute worst local dirt you can try to grow stuff in. It's fill sand left over from construction clean up fifty years ago. It's a golf course so they did a LOT of leveling and contouring and they seemed to love sand. I initially dumped a few yards of composted horse stable cleanings and each raised bed has since needed to be raised up beyond the original height with another course of 2X4s or 2X6s. Dirt shrinks, soil grows, so to speak if you're relentless about composting and recycling garbage.

Oh, yes, to stop pontificating and actually answer your question: landscape fabric from the big box store can work to stop dirt from sifting down into gravel. There's little else that costs as little and that lasts as long.

I also don't think there would be pressure on the fence...depends on the fence of course. I have such a setup that is about 2' high, maybe a bit more.

It does discolor the other side of the fence and I used a corrugated plastic barrier. I use old political signs as a barrier. Thin plastic doesn't last very long. EPDM is very good. But the fence still stains because some water does find it's way between the plastic and fence. A plastic mesh between the fence and plastic might reduce that, but never tried it.

The main reason I use a corrugated plastic barrier is just to slow down water loss. Concrete sucks up water pretty fast. I also think/hope that the openings in the corrugated plastic may reduce heating the soil as I install it with the openings vertical.

It's a myth that rock helps with drainage. It depends on what is mixed with the rock. If air, it drains fast. If coarse sand, it drains well. If clay it drains very slow. In all cases the material between the rock will always drain faster without the rock. Just air drains fast. Just coarse sand drains faster without rock. Just clay drains faster. This is because rock is denser than all these materials.

Any fabric that stops clay particles from flowing into the rock would drain slower than clay...because it has to be more dense than clay. So the fabric becomes clogged with clay.

And as grubby already said, more soil is better for plants and rocks reduce the amount of soil.

What I did with 3/4" granite that was in my yard was pile in into mounds and planted cactus and such. Looks pretty good I think. The rock also had a lot of organic material that had built up over the years so it's not just rock. I also dug some trenches like 3' deep and pushed the rock into that. I used the soil to create other mounds and plant cactus in the rock beds.

I see some basic problems with your garden. You will have difficulty reaching 40 inches across your garden. Try it! The maximum viable reach is 24 inches. Also the wall will block a lot of sunlight. I recommend moving the raised garden at least 24 inches away from the fence and having the garden 48 inches wide. This way you can easily reach your crops from either side⦠and you wonâÂÂt have to worry about the fence soaking up water and leaving calcium deposits. The height need only be 12 inches unless you are worried about wildlife or pets. DonâÂÂt bother with stones for drainage. Good soil will take care of the moisture.

I also have a raised bed made of cinder blocks. It is 24 inches high, 48 inches wide and 140 inches long. I put slate on top and fake stone on the sides. See the picture. I grow my tomatoes hydroponically at the end of the garden. I did not use a plastic interior or coat the cinder blocks with tar. I have 12 inches of quality soil (compost, peat and vermiculite) on top and local dirt below. The good soil could be Square Foot Gardening Soil Mix from Home Depot or go out to Singh Farms (NE Corner 101 Loop and Thomas Road in Scottsdale). They are only open Saturday mornings for compost. They have various mixes available. Just tell them what you want. You can either buy compost in large burlaps bags (takes two men to handle) or they can fill the back of your pickup with loose compost for about $60.

I also recommend Square Foot Gardening as developed by Mel Bartholomew. It makes the best use of your garden area and there is no room for weeds! Instead of planting in rows, you plant in grids. Buy MelâÂÂs book and read it. YouâÂÂll wonder why any gardener would plant in rows again!

I am very sorry but I really don't like your idea and I agree with steve there is going to be issues down the road. The plants next to the wall may not get enough sun also the soil will discolor your cement wall and the neighbor on the other side may not like it. Away from the wall, you can pick from all sides and not worry about drainage into your yard or the neighbors.
I would diffidently suggest about 2 feet deep.
I have enclosed pictures of some of mine. Hope it will help
Camp Verde
PS cost for ea. is about $20 not including the dirt

This post was edited by campv on Fri, Dec 19, 14 at 17:06

I think it might be a problem to build up against the wall too- more for sunlight reasons than pressure. How much light does that area get?

And I would worry about straight stacking the brick instead of stagger stacking. I would either stagger stack or use some hefty stakes or metal stakes to help prevent buckling of your bed wall.

I wouldn't use landscape rocks or any other rocks in the bottom of your bed at all. Rocks have a habit of working themselves up- I know this from much frustration in my yard where the previous owner used a lot of gravel in a lot of areas. I've had to scrap entire sections of garden planning because of gravel work ups.
In my raised beds, I've started out with a bottom layer of several sheets of newspaper, then layered in leaves, spoiled straw, grass clippings, egg shells... then started layering in my compost and soil. And heh, even with prepping that way, I still sometimes find a rock or two that has worked it's way up from the bottom!
And there is the excellent point of you want to make sure you give your plants as much depth as you can, and filling the bottom with rocks is counter-productive to that.

I wouldn't worry about making your bed 40 inches wide- depending on what you plan on growing in the back, and if you plan on giving yourself room to step into the bed if needed to reach the back of the bed. My raised beds are either 3 feet or 4 feet wide, but I have access to both sides. And I'm short- my hubby is tall with long arms and has no trouble reaching across the beds.

Beesneed... is pretty much right on all accounts You can use rebar to help keep the sides in line and keep them from budging. If you look close a the pictures you will be able to see the rebar keeping those wood sides from bulging. I forgot to add if you get your beds right up next to the block wall it could generate more heat then tender plants need in the summer.
My beds are 4ft wide and 8 ft long its entirely up to you and your needs and the room you have. There are no rules.
Camp Verde

This post was edited by campv on Fri, Dec 19, 14 at 18:19

4x8 bed 2' deep...so two 2x12's high? That's six 8' 2x12's and it looks like six 2x4's as posts. For $20? Where are you buying your lumber cause I wants me some. Here in Phoenix that'll run almost $100 at HD or Lowes. For a 16' bed as OP wants that's close to $200. Them be some pricey veggies.

Building the same bed with concrete block is 1/2 the cost and will last much longer...your grand kids can use them. And dry stacked concrete block is reusable. You can even resell it on CL for 1/2 the new cost. Or buy on CL for 1/2 the retail and resell later for what you paid. Pine that's been in soil contact isn't very reusable after say a couple of years. It's total life in soil contact is highly variable, but not exactly known for long life.

CL has a post with what looks to be enough block to build the entire bed for free. See " Cement Blocks (67th Ave & Indian School)". CL is always my first stop for building materials.

Hello. You didn't say whether this is a new home for you. I spent the first year checking out the sunshine in our backyard. My backyard was a south facing yard. The back fence shaded the back yard almost 4 feet into the yard. Which meant I started my first cinder block line just over 4 feet away from the block fence. OR the winter garden would never get any sun. During the summer time, the block fence might radiate too much heat back off the fence.

My cinder block garden was 3 cinder blocks tall. 24 inches interior width. I started with 1 brick high. I found the roots didn't have enough room. So I went up to 2 bricks. Again, not tall enough for tomato plants if you bury your seedlings deep like many recommend. So, I went up to 3 bricks high. Perfect for me.

I agree with previous posters. If you make the garden too wide, you won't be able to reach all sides of the garden. Important when you are trying to find the peas within the vines, tomatoes under their leaves, or to pull radishes that are ready for your salad.

I put the blocks right on the hard AZ soil. I then added mulch, mulch, soil, manure, mulch, manure.... It took almost 3 years to get the perfectly blended soil for all sorts of vege's. Shoveling, raking, and spreading more manure did the trick. I mulched all my kitchen scraps I could. That certainly helped with the health of the soil.

Oh by the way, the soil won't bulge out or push the bricks away. At least in my case. Any extra water leaked between some of the cracks and down to the bottom of the bricks. Making sure you have enough water to absorb into the soil so your plants have a chance to drink before it runs out at the bottom. Good luck!!

One related observation: I have beds both "free standing" and against a block wall. None of them have ever shown any tendency to bulge out.

I think an explanation to people responding from out of the area is in order. Arizona has more sunlight than we can handle at times, so much common wisdom from other parts of the world about shading plants too much does not apply here. That's not a hard rule, just a good rule-of-thumb. Secondly: we have extremely dry soil that will not exert sideways pressure no way no how (well, maybe if you drove on it). You can bet the ranch on that.

1. You can put the gravel at the bottom. I doubt it will do much either way.

2. Before you put down the gravel you might want to lay down a layer of hardware cloth of 1/4" - 1/2" to keep the gophers out.

3. If you want to lay down a weed blocker (landscape cloth) that too can help keep grasses from withing their way up.

4. As for staining the cement wall as long as you own the wall I do not see how what you do will effect the neighbor's side of the wall.

5. I agree if the area to be gardened exceeds 30" in width of soil it will be exceedingly difficult to reach the back without compressing the soil in your garden as you lean in.

6. Consider whether you want a trellis in back.

7. I would mortar it up and paint the block white.

8. Keep in mind your proposed bed holds 4 cu yds of soil. So you will not be able to afford a high end soil. But I agree Singh's compost if you live on the east side can be a cheap way to go. Pickup bed truck holds 1 cu yd. It may need to condition for a season meaning you can use it but it may improve the following year.

Waterbug that is what we spent no kidding. That would be 6 boards. The ends are 8ft cut in half so 2 boards on ea side and 1board ea end cut in half 4 ft. We bought the wood at HD. The 2x4 are only 2ft high and were the cheapest they are pine. As for lasting... the beds are over 10 years old. I am not against the block and NEVER SAID I WAS I did not like idea of it next to the block wall or the beds being less than 2 ft deep or filled w rock. I was showing what we had just for suggestions.Before you get all ruffled you need to read what people actually write.

Campy, calm down. Why so defensive? I'm not ruffled...I'm jealous. I want to know how you get that wood for so cheap because I want in on that. HD here charges a lot more than where you are. But I understand if you don't want to say where your HD is.

You said your beds are 2' deep...now I'm thinking only 1' high and the other 1' in dug out? So the 6 boards are 2x6 or 2x8? Here in Phoenix that would cost $31 for 2x6's or $62 for 2x8's and $5 for a 12' 2x4. So $36 to $67 total. You're paying almost 1/2 as much as me just for the lumber. So not as good as I originally thought, but still, 1/2 is a big savings. I could afford to drive a long way to save that kind of dough if I bought enough...and if you were willing to share what HD you're shopping at?

Adjusting for a shorter wall the price difference here in Phoenix isn't as great. A 16" high 4'x8' block bed would cost $42 or $62 in wood. So only 1/3 less. For new material. Block is pretty easy to find on Craig's List of course for cheaper or free at least in Phoenix. But yeah, if I could get even a 12" high bed for $20 in wood I'd say that was very much considering. I just don't know how I can get that deal.

The wall might actually be beneficial to you. Depends on what you want to grow. I believe most people here recommend growing tomatoes against an east facing wall as full sun in the AZ summer can be too much. I planted tomatoes against an east facing wall and they did pretty well all through the summer.

Hi Everyone,

Thank you all for your feedback. I'm new to this site and didn't realize I received any responses to my posting. I thought email notifications would be sent out. Below is some more detail based on some of the questions.

1. Regarding the spot selection. I chose this spot because I thought too much Arizona sun would be bad. This spot only gets sun towards the end of the day for a couple of hours. My house is east west, with my backyard facing west. It is not a new house. This is also the best choice in my yard. Will this be a problem?

2. Regarding being able to reach the whole bed. It actually only ends up being one and a half blocks wide (24"), so I think this should be fine.

3. Regarding using the landscape rock under the soil. Based on everyones input I will avoid doing this.

I have dry stacked the blocks and am now ready to reinforce with some rebars. Once that is all done, I will begin researching the soil. I hope to have everything ready to do some spring planting.

Thank you again for all the help.

I lose track of threads all the time too,

Not sure how the rebar is to be used but I wouldn't bother unless you're filling the blocks with concrete?

Pounding rebar into the ground to reduce bulging is a wood thing. Without something bonding each block together rebar won't do much of anything.

Dry stacked alone should hold. Over time however you're likely to have blocks move a bit, especially in the top course as they're bumped. Not a huge deal imo. For a build like this I fill the block with soil and tamp down every 2-4" or so. In my yard adobe clay is about 24" below topsoil so I'd use that. But topsoil works good too. That increases the mass of each block, requiring a bigger bump to move. Also a bond is created between each block making it much harder for blocks to slide out of position.

Using bond beam shaped blocks instead of regular also gives more area for soil to lock blocks together. But regular block is fine too.

Just to give you an idea here's a retaining wall I built a few days ago that's 30" tall and holding back 36" of soil. The wall is about 16' long.
{{gwi:2123007}}
This is dry stacked broken concrete so not a lot of contact between pieces. A very weak structure. But still the soil behind the wall was tamped so a fair amount of pressure against the concrete and didn't have any movement issues. It doesn't take a lot to hold back our soils in general.

{{gwi:2123008}}
I did place corrugated plastic behind the concrete to reduce soil washing through the huge gaps in the wall.