One foot deep is not very deep for a raised bed on concrete - unless you are only planting very shallow rooted plants they are not going to do well. They are going to heat up on that concrete and cook any roots that touch them. Roots like it cool.

If you are going to use them - and there are several of them? you might want to check local nursery suppliers to see if they can deliver bulk soil or compost. Otherwise bags of stuff is the only way to go.

I'd be a bit worried about chems used in the finishing, etc.

but yes - buying quality soil is a pricey business. Can you start composting?

I have raised beds, and I bought a yard of garden soil at a very reputable place, it was 1/3 compost, 1/3 top soil, and 1/3 pine fines. I rented a pick up and everything. And then had to hose down the inside and all that.

A huge amount of work - and then after a few waterings, the top caked over....clay! My tomato plants just sat there for a few months without growing at all. I was furious. That bed is still a problem 5 years later, and underperforming despite all my care taking.

So take care when buying soil! And good soil is expensive!

I now buy very pricey bagged soil for my starts and containers, so some of that gets transplanted yearly into the beds, and then I am composting everything I can get my hands on, and all that to try to build up the soil level (quantity I mean in this context).

I can't afford a whole bunch of pricey soil - and not taking chances on bulk buying again.

But still - the bed levels shrink each year as the organic matter breaks down. And I want to do additional beds as well. But accumulating soil is either going to be expensive or time consuming....

And just to clarify - I'm in the city. More rural areas have access to loads of materials I'm sure. Not so here, and I don't want to take in other people's yard wastes for fear of herbicides that'll stunt the veggies.

My back yard also sags in the middle - so I need more soil just to even out the lot, LOL!

Good luck!

I plan on taking shelves out of, flipping them onto their backs, and using them for (atleast temporary) container gardens on top of concrete.

No direct contact with the concrete. If these have a back on them then put 2x4 spacers under them to raise them off the concrete so air can circulate under them and remove some of the heat. This is if you have no choice but to use them on concrete. And drill drain holes in the backing so water can get out.

As to filler - your best bet IMO is to make your own using one of the recipes provided over on the Container Gardening forum here. Check out Mel's Mix and the 5-1-1 recipe there.

Dave

I agree that the only real concern should be the chemical used as finish. and that can be sanded off.
The other issue is dranage that Dave provided solution.

Somebody said to the extent that the bed wiil cook on concrete...
I don't think so.The concretr around the bed can/might get warm and reflect some heat but the part under the box will be at ground temperature, even possibly cooler. Remember that concrete is no a good heat conductor.

And one foot depth, as already mentioned is not at all TOO DEEP, considering that you fill it couple of inches lower.Also,because the bed is sitting on concrete(insted of soil) a deeper box can have advantages.

Our landfill has certified organic soils available for very reasonable prices. They have a garden mix and many other mixes. You can also go to a landscape place that will sell to you by the yard (some even deliver!)
I respectfully disagree with seyson. Concrete/cement absorbs heat and along with the sun reflecting....can get quite hot!
Think about the temps of the city VS the temps in the country! All of that city cement holds onto the heat! Also, think of your feet as a kid walking on a hot sidewalk!
I'm agreeing with the others who say to have some air circulating underneath the boxes!
Also, check out the container gardening forum for more info! I'm also new to container gardening and am learning a lot from them! Nancy

Nanctjane,

It is just a perception that concrete can conduct heat, BECAUSE IT GETS HOT. Actually, if it were conductive, would not get as much hot(would cool off faster).

here is heat conductivity of some materials ( W/m.K):
asphalt -----------.75
brick ................. i.5
concrete -dense --- 1 to 1.8
clay --------------------- 0.6 to 2.5
EARTH -DRY --------- 1.5

so dry earth is just about as heat conductive as concrete is.

Another thing is that heat will thake the shortest rout to travel, i.e. mostly vertical and much less horizontal.This is the conduction part. Radiation part will travel outward in all directions

Therefore, the heat due to the concrete underneath the container woud be minimal

I just want to thank each and every one of you. You guys have been amazingly helpful. I'm new to this site and I think I'll definitely be sticking around to learn. It seems offline I get a lot of blank stares and very unhelpful answers when it comes to anything like this.

I only have a few of these containers and they will be on a mixture of concrete and rock that is part of a wall beside/above a creek. I am so ignorant about gardening soil at this point that I had been hoping I could maybe use a portion of the soil in my own yard combined with bagged potting soil to save money, but i guess I will invest in decent soil.

I am so glad that a couple of you mentioned the potential dangers in any finishes on these cabinets. I hadn't really thought about it before. The cabinets are not solid wood....they are a (somewhat) decently made fake wood that I have no idea what it is and I don't think I can find out either. T
The backs of the cabinets (which would be the bottom) are that very flimsy thin wood grain appearance stuff that you would often find in the backs of entertainment centers. I knew they would probably rot easily, but I was only hoping to get atleast one season out of them. But now I worry about any potential toxins or chemicals.

Would a heavy duty plastic liner be ok? Does anyone have tips building large wooden containers about this size? I'd really like to have a few big containers of some sort to help disguise this unsightly wall this summer.

Also, how deep should they be for just general veggie planting?

Thank you again everyone, I truly appreciate the help and will start reading around the site more.

Building a container can be pricey, but if you use cedar planks, it can be done for about $15. Home Depot will even cut them to size for you, then all you have to do is screw them together. Be sure to use a 2x4 in the corners for stabilization. You can just lay a "weed block" plastic for the bottom if the container is on stable ground - no need to make a back for it.

There's also pallet gardening that people seem to have a lot of luck with. You have to try and find "heat treated" pallets though to avoid chemicals in the wood. Home Depot sells them for $10 each - you'd just need one. I'm trying it for the first time this year, so it's too early to tell if it'll be successful. But it appears to work well for herbs and shallow-rooted plants, such as lettuces. You can even do those as a vertical garden with just a bit more effort (and burlap/chicken wire).

My school garden on asphalt did just fine. It's just not a good idea to let trailing plants hang over on the asphalt because they will get hot. One foot deep is fine, too. The only concern is the paint or finish on the bookcase. You can sand it to remove it. If you drill a few drain holes on the sides near the bottom, there is no reason it has to be off the ground.

You could custom build from 2x6s or 2x12s very easily with the benefit of customizing the size. Not free, but not pricey either. Cedar would be more expensive, but I have a bed constructed of just anonymous wood from home depot.

I bought 3 2"x12"x10', and had them cut one of them in half - voila! a 5x10 bed. 3 screws at each joint (about 3.5 to 4" screws) and you are ready to fill.

The wood is getting a little soft feeling, about 5 years later. I bought expensive cedar for some other beds, but not worth imho. I'll go with the anonymous wood at home depot.

Seysonn is right about the heat. Concrete is a mediocre conductor. It is also a mediocre absorber. Concrete in the sun is MUCH cooler than asphalt (aka blacktop and macadam), for example. If you paint the concrete brilliant white, it will be even cooler. But I think that is a non-issue.

I build raised beds (and have built planters) out of 2x12 fir lumber. It is relatively cheap and lasts several years before rotting out. If you build a planter from 2x12 lumber, line it with black plastic polyethylene sheeting and lift it up off of the ground a little, it will last for many years, I believe. You can paint the outside to make it look nicer.

I'm not actually sure how safe polyethylene sheeting is from a chemical perspective because I don't know what kind of additives they may put in there besides the polyethylene. But I have done it before. They also sell pond liners, which, since people put fish in ponds, should be safe. Fish are very sensitive to toxins in the water.

You do need drainage holes at or near the bottom.

I have had good luck mixing perlite, compost, and peat moss in equal proportions (almost mel's mix), but the container gardening forum suggestion that someone made is probably a good suggestion.

I think 5 feet is too wide for a planter or raised bed. It is hard to reach the middle. I think 3 or 4 feet is about right, depending on how long your arms are, and to an extent, how young and flexible you are.

--McKenzie

You can grow in containers right on an asphalt driveway. Check out nctomatoman's videos on Youtube - he grows a lot of plants to breed tomatoes and peppers, and many of them are on his driveway. The pots and the plants shade the surface.

I just want to point out that if there are toxins in the finish, sanding it will most definitely put you at a greater risk of harm than using the wood as a garden. The worst thing you can do with a toxic finish is sand it, inhaling all that dust straight into your body.

However, from the original poster's description, these sound like particle board kind of bookshelves. Therefore, I'm guessing, probably post-1978 and if so, no concerns about lead at least. I'm not sure if there are other things to be concerned about (since furniture usually is pressure treated, either).

I do agree mckensie re 5' wide beds potentially being too wide. For me it seems fine. Mostly.