Author Topic: Raised beds on concrete  (Read 4678 times)

shelivesthedream

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Raised beds on concrete
« on: June 25, 2017, 04:26:09 AM »
My garden is 100% wall-to-wall concrete. On top of that, some enterprising person in the past has laid out beds in brick. They are one or two bricks high and filled with large pebbles and gravel, and most of the edges are a bit aesthetically curvy. There is no organic matter in the garden.

I would like to increase the height of these beds so I can fill them with topsoil and grow perennial flowers in some and have one for vegetables. (I'm going to try square foot gardening). Most raised bed advice is either for raising beds on soil (so you can hammer stuff into the ground) or on a patio (so there is nothing there already to dictate dimensions and you just build a big box).

I have DIY skills but am not physically strong. Hefting massive railway sleepers or concrete blocks around is not on the cards. (My husband and mother are slightly available for helping.) I'd also, to some extent, be willing to spend a bit of money to make life simpler. I'm also only here for three years, so I don't need something built to last twenty. What do you recommend I use to raise the bed walls?

deborah

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Re: Raised beds on concrete
« Reply #1 on: June 25, 2017, 04:50:30 AM »
When I was a student, living in poor housing, every house in the street had a concrete back yard, and the houses opened directly onto the street. The people two doors down had a wonderful back garden. They had all their plants in plastic pots, and had put soil between the pots (the pots were round, and there wasn't really any room between them). This had naturally gravitated to form a soil layer under the pots. It looked like a well planted garden, whereas it was just pots, that were completely removable if and when they ever moved house. They did have paths between the "beds" - just the original concrete. I can't remember if they actually had any retaining walls for the "beds", but I don't think they did. They watered their garden the same way that you normally do, because the pots all protected each other from drying out.

Cranky

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Re: Raised beds on concrete
« Reply #2 on: June 25, 2017, 05:40:36 AM »
I think really big pots might be your best solution - you can get them made out of some sort of plastic stuff that looks like ceramic, but is much lighter and easier to lug around. They aren't cheap, though. I look for them at the secondhand places, at yard sales, and on clearance in the fall.

shelivesthedream

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Re: Raised beds on concrete
« Reply #3 on: June 25, 2017, 06:29:59 AM »
I'm not anti-pots but I have two that are busting out of their big pots already, as well as lots of smaller pots. And pots are hella expensive, even the cheapest plastic ones, once you get to that size. I'll look into it, but my initial researches suggest the cost will be much more than raised beds. Any tips on where to look for big pots? (That I can buy now, not collect gradually over the years.)

Cranky

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Re: Raised beds on concrete
« Reply #4 on: June 26, 2017, 05:10:48 AM »
They have great big ones at the big hardware/gardening places, but they are more than I'm willing to pay. Sometimes you can get wooden half barrels pretty cheaply, and those look nice. I bought a couple of pots big enough to plant a ficus tree in at Aldi's last year.

I've seen raised beds that are actually on legs, and that would work in your situation.

Or, you can just build up the beds you have - using landscaping brick - and fill them with dirt on top of the gravel layer. I feel like there might be drainage issues, but it's basically the same as a big pot, so maybe it would work well.

former player

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Re: Raised beds on concrete
« Reply #5 on: June 26, 2017, 06:49:46 AM »
Anything you build needs to be able to drain.  Which also means that it doesn't have to be that well built.

I don't think you need to build high: a foot or even less would do fine for lots of flowers and vegetables that have shallow root systems.  So don't bother with root crops and perennial flowers and shrubs, go for leafy green veg and annual flowers, with perhaps a few evergreens and climbers in pots to give you something to look at in winter.   The thing to watch out for with shallow beds though is the need for regular watering: they won't hold water nearly as well as deeper beds.  If you look for flowers which do better in dry conditions they will look good with the gravel and pebbles you've already got (see Beth Chatto) and let you concentrate on keeping the leafy green veg doing well.

I would avoid the usual DIY stores and try a builders' merchants' that can deliver materials - more bricks seems ideal for you to build up the beds you've already got.  I don't know whether a builders' merchants can do topsoil, but someone around you will and will deliver- check out ton bags for an idea of amounts and costs.

Pics in due course, please!

Fishindude

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Re: Raised beds on concrete
« Reply #6 on: June 26, 2017, 07:11:55 AM »
My raised beds are built on top of a slab and they have worked well.   Had an old chicken house that we tore down and left the slab in place.
Built (4) 4' x 16' raised beds about 30" high out of 6x6 treated timbers.  Filled the bottom 12" or so with large gravel, then the balance with good topsoil.  Have never had any drainage problems, just the opposite, the raised beds tend to dry out quicker than a garden planted at ground level.

phred

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Re: Raised beds on concrete
« Reply #7 on: June 26, 2017, 01:21:28 PM »
if pots are to expensive. why not try storage totes.  They are frequently on sale at many big box stores.

Hotstreak

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Re: Raised beds on concrete
« Reply #8 on: June 26, 2017, 02:04:33 PM »
if pots are to expensive. why not try storage totes.  They are frequently on sale at many big box stores.

They last fine for a few seasons, but the weight of the water and soil will push out the sides and eventually they will break.

OP have you looked at nursery supply stores?  15 gallon pots are about $8 USD where I live, not too expensive.  They are sturdy and will last many seasons, and are also easy to move if you want to live somewhere new.  There are smaller sizes too, I only use 15's for large tomato plants.  You can purchase accompanying black plastic saucers to catch run off water, which will prevent the concrete from staining badly.

If you don't have access though, look online for fabric grow bags like the link below.  These are a bit messier to move since they are porous, but overall a fairly easy solution.  Their soft shape allows you to customize how they fit together.. so they can be more aesthetically pleasing than the black nursery pots.  I don't have any personal experience with these, but the concept it sound.  You may need to water more often with them.

https://www.amazon.com/247Garden-5-Pack-Gallon-Aeration-Handles/dp/B013JFHMQ2/ref=pd_bxgy_86_img_2?_encoding=UTF8&pd_rd_i=B013JFHMQ2&pd_rd_r=PGC57DHWCH8QJDZBX6BM&pd_rd_w=Ex9lc&pd_rd_wg=zc7By&psc=1&refRID=PGC57DHWCH8QJDZBX6BM

Spruit

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Re: Raised beds on concrete
« Reply #9 on: June 27, 2017, 02:59:48 PM »
You can also use mortar boxes or buckets, they are pretty afordable when bought in bulk at a DIY wholesale shop. Drill some holes for drainage of use something like pottery shards to add a drainage layer on the bottom.

Dictionary Time

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Re: Raised beds on concrete
« Reply #10 on: June 27, 2017, 03:43:36 PM »
I'm going to offer up stock tanks. My local farm store has a 67 gallon galvanized one for $70. (I'm not sure if that's a good price- just throwing it out there)

They would hold a lot of dirt, and a number of plants. That would cut down on the drying out problem you run into with pots.

They're durable- designed to be out in all weather watering animals.

The galvanized metal is kind of a retro country mason jar style these days.

GizmoTX

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Re: Raised beds on concrete
« Reply #11 on: June 27, 2017, 03:53:11 PM »
Crates, as in dairy crates, lined with garden fabric & filled with soil. I haven't done this yet, but it is intriguing.
http://modernfarmer.com/2013/08/meet-tom-colicchios-urban-rooftop-farmer/

letired

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Re: Raised beds on concrete
« Reply #12 on: June 27, 2017, 09:10:33 PM »
+1 doing shallow-rooted crops.

Can you dismantle one of the beds and use the bricks to build up another? That would be an easy and low-cost way to get the increase in depth. You could also increase the depth factor by removing some of the gravel thats already in the bed.