In-ground garden beds possible?

jeff_12422August 13, 2013

We have a LOT of mesquite and acacia trees in our neighborhood, which are protected by the HOA (can't cut down/remove any native plants, and we really don't want to, b/c they provide some shade) but their placement on and around our property means that the roots interfere with any location we possibly have to put in a garden.

We built a small raised bed where we thought we'd put in the garden, and it did OK for the first season or two, then went south. Couldn't figure out if it was the water supply, etc. Then I dug it all up and found that the neighbor's mesquite tree (whose branches overhang the bed) has roots coming up through the hardware cloth in the bottom of the bed and they basically filled the entire garden bed and sucked all the water away from the veggies.

There are two trees on that end of the yard, one in the middle of the yard, and an acacia growing on the other end where the chicken coop is going to be. So they'll need that for shade (nevermind that chickens + in-ground beds = no food for us).

Any suggestions on how to go about this? I wouldn't mind container gardening but with as many as we'd need, it would look horrible. I'm talking about food production, not just a 4 x 12 garden bed.

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tomatofreak(Z9 Phx USA)

Interesting question. Could you possibly post a photo - or 2 or 3 - showing the areas you have in mind? Also, have you attempted to dig in one of your preferred locations to see if you've got rocky soil or caliche?

    Bookmark   August 17, 2013 at 3:48PM
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I'll try to post some photos as soon as I can find the cable for the camera.

I think we have caliche. We were planning to get in some heavy digging equipment to excavate for the beds (and still will have to for sinking containers if that's how we decide to do it).

Basically, the only areas we have that are far enough from the mesquite trees to grow in-ground are very close to the house which is where we have the kids' play areas and patios. And of course before we realized it, we put the shed right in the only bare spot, thinking it was perfect there b/c there is no shade there to protect the plants! argh

    Bookmark   August 24, 2013 at 6:07PM
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Man that is tough. Don't take this the wrong way, but being able to landscape however I want is the main reason I won't live in an HOA. I can easily put up with the neighbors, as long as I run my own yard.

I'd suggest looking into "wicking beds". I'm talking the big ones people build into the ground. They are popular in Australia where I believe they have strong water restrictions, and dry heat like us.

The idea is to water from below. Use some real thick plastic and landscape fabric to make sure water doesn't seep into the ground where annual veggies can't reach them. Each season you are replenishing and turning soil. That's what I would do to keep those tree roots out of your beds.

    Bookmark   August 25, 2013 at 7:02PM
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Here you go... I DID make one of these I kept for a year, in a 4'x4'x18" bed. Spring planted two tomatoes plants in there and they did great. The problem is buying the planting mix that most guides suggest. Assuming you have clay since you mentioned caliche, to get the capillary wicking action you really can't use too much native soil... Find some bulk potting mix from a reliable source, I would also do that.

    Bookmark   August 25, 2013 at 7:14PM
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Those wicking beds look neat! Thanks for the links.

I took a few pics, but it looks like I can only post one at a time... So here's the first one. More to come.

This is the north part of our yard, out the side door from the kitchen. That's the most logical place for a garden since it's closest to the door we use from the kitchen. Note the two mesquite trees hanging over the wall -- their branches extend out as far as their roots, which is why those vines aren't doing as well as the nurseryman said they would.... And we'd like to keep some of that area to the right clear so we can use the gate if necessary.

All the cacti will be removed/relocated.

    Bookmark   August 27, 2013 at 4:11PM
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And another pic of that same area (with gate).

    Bookmark   August 27, 2013 at 4:13PM
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This is the other side of the yard, where the chickens and compost was supposed to be. The compost was going to be next to the shed, with a sink in the corner (we're removing that desert broom and the oleander) and then the rest of the area for cover crops for the chickens and the coop to the right.

    Bookmark   August 27, 2013 at 4:15PM
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Last pic... The acacia tree will stay, with the coop to the right of it. The area between the house and the rock "river" you can see in the pic is the kids' play area. Giant mesquite tree to the right in this pic has branches that extend all the way over to the acacia tree, so that's good shade for the house (western exposure) and the chicken area, but not so good for sucking water away from any in-ground plants/on-ground beds.

The woman who was helping us plan this had suggested raised beds to begin with, but she likes to use those metal horse troughs. I like the idea, but not how they look when there's more than a few of them. Would it make sense/work to sink some of those into the ground, or is that a stupid idea? (I'm a total newbie, so I have LOTS of stupid ideas... I won't be offended!)

    Bookmark   August 27, 2013 at 4:20PM
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I don't see a problem with the horse trough idea, but galvanized metal will eventually rust through.

I'd consider those large, molded plastic ponds they sell at HD and Lowes. At least they won't rust (I'd bury them to keep them out of the sun.) I was thinking of the same thing.

    Bookmark   August 30, 2013 at 9:36PM
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That's an idea. But won't the plastic crack and leak/let roots in? (I have no idea....) and what about chemical leaching from whatever material the trough/bed is made of, whether that's the metal or plastic? Is there any material that is better/worse for that kind of thing?

    Bookmark   August 31, 2013 at 2:25AM
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MaryMcP Zone 8b - Phx AZ

You certainly have a tough problem with those tree roots. What sort of drainage solution does the person suggesting galvanized horse troughs recommend? If you drill holes for drainage, the roots will find their way in. A thick layer of pebbles might work but those troughs will need to be underground, they will be too hot in summer.

I have read quite a lot about wicking beds and like that idea. You could use pond liners instead of heavy plastic. I don't know what its makeup is that is different from heavy mil plastic but fish swim in the ponds, and turtles etc. Anything like that has the potential to spring a leak, you will have to be very careful with your shovel.

Good luck, I hope you can make it work for you.

    Bookmark   August 31, 2013 at 9:15AM
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hey mary, you bring up a great idea- using a pond liner membrane. But I think my idea of using plastic molded ponds would be sturdier.

Jeff, I wouldn't stress over chemicals coming from a molded plastic or even the galvanized metal troughs. Cured plastics are quite inert (think drinking water sold in plastic) And if you use metal, zinc is an essential mineral that plants need anyway.

I'd put a drain hole in the low spot of whatever container you choose and connect the drain hole to a fitting that is attached to a pvc drain line. That will allow drainage, but won't allow tree roots to get in if you can monitor the end of the drain pipe (like have the pipe drain into a gravel filled dry-well.)

    Bookmark   August 31, 2013 at 3:43PM
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MaryMcP Zone 8b - Phx AZ

Yes you are right rich, the molded plastic would hold up better although it may crack at some point, its lifespan will be longer than the pond liner. But less than the galvanized tank. I like the description of how to drain it. Great minds here!!

I'd sink anything into the ground regardless what you decide jeff. Keep in mind the point mikerizzle makes about the cannot use 'dirt' in a container, it's too packed, you need to use a good potting soil.

    Bookmark   August 31, 2013 at 5:03PM
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Hmmm... I'll have to look into those options. Very good ideas!! I like the way the drainage would work for the sunken troughs -- I was wondering about that, and then wondered if we really even need drainage -- it seems strange that we'd need it when we are always so desperate for water. If we put in a layer of rocks/boulders/some other large loose material in the bottom, do we still need a drain?

As for "dirt" v. "potting soil".... Does that mean I shouldn't be using the mix of sand, peat, manure and vermiculite I've been using?

    Bookmark   August 31, 2013 at 7:30PM
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tomatofreak(Z9 Phx USA)

"Does that mean I shouldn't be using the mix of sand, peat, manure and vermiculite I've been using?"

If you're using the 'recipe' put together by Duane Clupper, famous for his "garden in a bag" program, then by all means keep using it. It's a great soil mix! I put together a community garden once under Mr. Clupper's tutelage and the results were fantastic.

Btw, gardening in a horse trough can also be an excellent alternative to raised - or sunk - beds. Visit the DBG and have a look at their veggie/herb garden. Lots of galvanized troughs there.

I've raised peppers, greens, sweet potatoes and some other veggies, too, in a simple plastic kiddie pool (with drainage holes) sunk in the ground.

My advice: Experiment, get creative, try whatever comes to mind and don't overthink it.

    Bookmark   September 1, 2013 at 2:53AM
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1. Everyone's garden competes with roots, frequently palo verde and mesquite. What you meant to say was you didn't water your garden often enough and everything died. You water when the soil needs it not on a schedule. In the summer you can figure it will be every other day of the soil has enough humus and you mulch and the bed is deep enough. But you should always test the soil daily for moisture.

And if your neighbor's mesquite trees are sucking water, then you need to water more. It may be possible to sink a contiguous slab of concrete wall deep (at least 18" down, and frankly I'd shoot for 3-4 feet to keep tree roots out. You should only be watering a vegetable garden to a depth of 1 foot/ watering. If a trees roots don't encounter water they die back. Roots don't like to grow up so restricting them by putting a wall in the way and denying them water can help. Tree roots mostly stay in the upper 3 feet of soil. But I don't think it will prevent tree roots from eventually occupying a bed.

I suppose it is possible root barrier fabric (instead of concrete) would work as a barrier, but it would be keeping roots out not in so that would be different...and it would be expensive in the lengths needed.

And also likely, you didn't add nutrients back every planting and the nutrients ran out. This would account for the third year failure as much as not watering enough.

2. A fully contained garden will work provided it is fully contained and you don't mind the expense.

3. I note the drainage pebbles along the contour line of your back yard. Were it my property I would seal off the draining exit into my neighbor's property, protect the inlet from another neighbor's property and let that precious water flood my yard. Ditto on roof gutters to direct the water to where I want to plant it if HOA doesn't have a rule against that.

    Bookmark   September 1, 2013 at 5:52PM
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As far as raised bed goes you can make some fine looking raised beds out of wood. What I don't like about raised beds it increased heat, increased evap from having exposed sides.

This can be ameliorated by building a bed within a bed: Have two wooden walls (untreated cedar or redwood if you can afford it) topped with a 2 x 10 all the way around which makes a nice bench to kneel or sit. This provides a insulative air gap filled wall between the bed and the outside temps. Pond liner optionally can be placed on the interior wall to minimize wood rot and cut down on evap as well as any wood treatment leaching into garden. I would use landscaping cloth landscape stapled to the ground for drainage and to block roots. Need an 18" bed for thermal mass and moisture retention buffer which will be expensive unless you use your own soil and have a decent amount of finished compost in a 50:50.

Keep at least a 3 foot space all the way around the garden for access. Limit garden bed width to four feet for easy access. Consider adding a trellis post in the middle to grow up.

    Bookmark   September 1, 2013 at 6:21PM
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Thanks for all the ideas and advice. I really don't like the look of raised beds, and don't like the expense/extra heat/evaporation issues either. But maybe they would be something to consider in the areas near the tree roots, and then maybe do in-ground beds in front so we can do both.

Fascist_Nation, you have given me a lot to think about. We had/have all the irrigation on a daily timer. So I'm guessing the bed got watered too frequently and not deeply enough. It just doesn't seem like that's possible, but I guess it is what it is. I never actually tested it, and then when I was going to see how long the irrigation needed to be on for it be water all the way down, that's when I discovered the entire bed was tree roots. So I haven't managed to find the answer to that yet, but you can bet I will before I start planting in whatever new beds we end up with.

I did add composted manure and peat every year -- is that not enough as far as replenishing nutrients?

And I'm a little confused about root depth.... If I do in-ground beds there, I'd need to create a barrier (you recommended concrete) to keep the tree roots out. If I do a concrete slab down to 4 ft and then dig the beds 2 ft deep and line them with landscaping cloth, that will keep the tree roots out? For how long? And how well does that cloth really work? The tree roots I found in the bed were very fine, and at first I thought they were leftovers from my veggies of past seasons. Then I found the mother root and realized the tangled knot that was my garden soil was all tree root. We have landscaping fabric underneath the red rocks all over the yard and we do still get weeds coming through it, so I have a hard time believing that the mesquite roots won't penetrate that. (Although I know the concrete will buy us some time.) Wouldn't the tree roots just grow down and then under the concrete and come back up for water in the garden bed?

The drainage pebbles are relatively useless right now (they were just for decoration, apparently -- previous owners put that in) but we are planning to redirect the gutters and drainage to the beds.

    Bookmark   September 2, 2013 at 5:17PM
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