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I just moved into a new place with a quarter circle bricked in fountain/pond in the backyard. I'm converting the it into a garden, primarily for vegetables. Here is a picture: https://www.flickr.com/photos/16589820@N00/5322325473/

I've demolished the stone structure. The radius of the circle is about 6' and the depth inside is about 18". It currently has a single drain hole on the left corner, about 1/2" diameter, going out into the dirt next to it.

How do I begin? I think I should add some more drain holes with a masonry drill bit, but how many? How should I line the bottom and layer the soil and other fill?

Lastly, there is a copper pipe coming through the bottom that was used to fill the pond. I have access to the valve and it is functional. Any suggestions as to how to best use this to hook up a watering system? Just looking for good ideas. I'm new to gardening but my parents did it a lot when I was growing up - though no container gardening.

I'm in San Diego near the coast.

Thanks!
Curtis

Since the "container" was watertight, I think you would need several drainage holes ... maybe space the holes about every 6 inches all around the outside.

How deep is the "container"? Is there a cement bottom, as well? Depending on the depth, some plants might not be able to grow there. Also, what is the exposure to sunlight ... east, west, north, south ... and is there anything blocking the light, such as trees, walls, or other structures? Do you plan to remove the fence that's blocking the sun from the one side?

As far as soil is concerned, I would recommend a high quality potting mix. With such limited drainage, anything else would retain too much water and rot the roots of anything you might plant ... regardless of how many drainage holes you might drill.

I'm sure someone will come along with advice for the watering system. I have an in-ground irrigation system, but I doubt that's what you'd want in such a small space. A drip irrigation system would undoubtedly work better.

Welcome to the forum.

Bottom: cement. Depth about 18 inches.

The stucco wall you see in the picture is on the south side, the fence is east. I can't remove either. There is pretty good sun exposure on west and directly overhead. Our home is on the north (behind the photographer). It is in partial shade most of the day except when sun is high over head to setting.

I'm planning on putting some rocks in the bottom before putting any soil, since good potting soil filling the whole thing would be a bit spendy, and it may improve drainage.

I was thinking drip as well.

Garden soil will stay too wet in the bottom 1/2 or 1/3 of the planter, regardless of the rocks and how many drainage holes you drill. You really need to use a good potting soil. It's a one time investment, and I strongly urge that you not try to cut corners on that aspect. You don't have to buy it in bags. Check with businesses in your area that deliver bark mulch. Such places usually sell a quality potting mix for outdoor planters. You can go there and buy a pickup truck load, if you like. If you need more than that, you can spread a tarp in your driveway and have them deliver a few yards of the stuff to you.

I understand I need good potting soil for at least the top.

Are you saying the entire depth of the container (18") should be potting soil?

I was thinking of putting 1 or two layers of rocks or shards from broken pots (maybe 5-6" depth), then going from there, but don't know if there are other layers I should use.

I saw [url=https://books.google.com/books?id=up4YiCywqJQC&lpg=PA16&ots=XtSuT91DQs&dq=large%20concrete%20garden%20container&pg=PA26#v=onepage&q=large%20concrete%20garden%20container&f=false]this reference[/url] in google books. There is a diagram on page 26 that I thought might apply.

(I edited your post slightly because the link was breaking the template. )

Years ago, when I first began gardening, I used to add rocks/broken crockery to containers in order to improve drainage. But after many years, I discovered that it didn't do much good, and in fact, often caused damage to the plants' roots. IMO, the only advantage to adding rocks and such to a container is to keep a tall plant from becoming top heavy and toppling over, or to keep the container from being blown over by strong winds. Your garden isn't likely to have either of those problems, so I would advise against adding a layer of rock. If I were going to add anything under the soil in a garden such as yours, it would be a layer of activated charcoal, to keep the lowest level of the soil from turning sour. That could be quite expensive, though, and is not something I would consider a requirement.

One of the problems I found with crockery or rocks in the bottom of a container is that the plant's roots grow down into that layer. Then, when you pull or dig up the plant at harvest (or to repot), those rocks come up along with the roots. They become mixed into the soil, where they do no good at all, and can interfere with root crops such as carrots. (Gardeners don't usually prefer rocky ground for their gardens.) Short of removing all the soil from the container and sifting out the rocks, you end up with no advantage at all. JMO, though. (As you can see, I am not a proponent of rocks or crockery in the bottoms of containers! )

Regardless of whether or not you choose to add rocks, and whether you do is entirely your choice, the only "layer" I would recommend would be a layer of mulch on the top to prevent weed growth. That should be about 3 or 4 inches deep.

Consider that, if you allocate 4 or 5 inches of the 18" depth to a layer of rock in the bottom, then add 3 or 4 inches of mulch on the top, your plants are going to end up with less than a foot of soil in which to grow. That makes for a really shallow garden, and not much room for the plants' roots. Whether that matters will depend solely on the plants you wish to grow. If you plan to grow greens and herbs, that's plenty of soil depth. If you were intending to grow tomatoes, though, it might not be enough. In general, a tomato plant requires about 14 inches of soil depth, at a minimum.

The idea of putting rocks, etc. in the bottom is long-standing but misleading as a working solution, especially in an outdoor fixed "container." The concept is being essentially debunked now-a-days for reasons Kisal described.

I would also use that masonry drill to drill holes in the bottom of the "container." I mix my own container soil mix out of about 1/4~1/3 my own compost with only the largest bits removed (I.e. lots of branches, small rocks, bits of pine cones, etc. that would also aid in drainage -- you could simulate this with composted bark if all you have is finely screened compost), 1/4 play sand/washed pea gravel (I've also used patio brick underlayment sand/gravel) and good soil from my garden -- a.k.a. good quality top soil. I amend this mixture with rock phosphate, green sand, and dolomitic lime, kelp meal, wheat bran, etc. depending on what I think the plants might need. I also sometimes add premium potting soil to this mixture. It's more economical than than using 100% store bought bags.

I know you said you wanted to grow veg's, but one other option is to use this space as a bog garden. You could still grow edibles like cranberries, water chestnuts, rice, arrowroot, Taro root, etc. There are other edibles that don't mind wet feet, too -- like celery. I want to say water cress, but I haven't tried growing them... yet. I'm exploring different things to grow in a wet bog -- I have a thread started in Water Gardening Forum if you're interested.

You might even be able to get rid of the bottom of the pond altogether with a cold chisel and sledge hammer...This would solve the drainage and depth issues.

I hadn't thought of breaking up the bottom. Especially after how sore I am today from busting up the waterfall structure...

But it might be the right thing to do. Another option I was considering:

adding a few more drain holes with a masonry drill bit into the bottom edges of the walls, then laying down a few pieces of 1 x 4 boards and a large piece of plywood with lots of holes peppered throughout. Laying fine mesh over the top of this (to keep dirt from washing down and bugs from getting up, then putting in my potting soil. This would provide a false floor under which drainage would be pretty good. It would only eat up about 1.5" of depth and provide about .75" passage under the false floor for water to drain down to which would then flow horizontally out of the drain holes at the base of the walls that I will add.

Alternately, I could just pepper the bottom of the pond with drain holes straight into the ground. I don't know how thick the bottom is, but I can try with the longest bit I can find. I was previously limiting my thoughts to putting holes around the perimeter through the wall and couldn't imagine that would provide enough drainage.

I think I've figured this out. Putting in a wood false floor is not a good idea as it will rot too quickly.

I bought a masonry bit and plan to start drilling some holes in the bottom tonight to see how easy it is and how thick the concrete is. If it is relatively thin, I will probably use a cold chisel and break it up a bit down to the dirt. If not, I may rent a jackhammer and do the job right. Either way, I plan on busting out the bottom so I get good drainage.

Thanks everyone for your help.