need help with building a raised bed

tambo747(5 Canada)April 2, 2009


I am building a raised bed in a corner of my backyard. It will run 9ft long along the fences and will be 4 ft wide by 2 ft high. The area is currently grass. My house is in a newer development (5 years) and I have heavy clay soil (I know...the idea of digging that stuff is hurting my back already!Damn builders!). I'd like to know what is the best way to approach this project. How much of the clay needs to be dug up? I've been reading about putting gypsum to amend the clay. I also read about gravel for better drainage. I plan on ordering a truck load of great soil from my local family owned garden center, but want the foundation of the bed to be perfect. Any advice?

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Hi tambo747 - I am in Calgary and have 5 large raised beds in the back yard, with two or three more being built this summer in the front yard.
I, too, have very heavy clay soil (which my roses love), so I hear you about your back!
While I levelled the ground the raised beds sit on, I did NOT remove any soil, but instead lined the inside of the beds with landscape fabric, and spread a layer of gravel before dumping the topsoil.
We grow veggies and winter hardy roses (and other plants) in the raised beds, and have done so now for a number of years with great success.
Every year I add nutrients to the soil, but that is it!
It may not be the most scientific, but it has worked for me!
Does this help you and your back??? : )

Cheers, Stuart...

    Bookmark   April 4, 2009 at 6:58PM
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I agree. 24" raised beds provide more than enough height for most vegetable roots.

I wouldn't bother with the landscape fabric or gravel. Over the years, if you add compost and use lots of mulch, the soil in your raised beds will develop some "life". The microherd and worms will move in and the organic matter will increase. Organic matter is a good antidote to clay.

Despite its penchant for breaking gardeners' backs, clay is quite "nutritious" for plant roots, as your roses will attest. It is also slow to wet and slow to dry. With two feet of good soil on top, it will likely stay moist all season. This is a good thing for any really deep-rooted things or perennial plantings you may put in your raised beds.

If you put two feet of soil on top of whatever is growing there now (grass?) that will be enough to kill it, but you don't really want dead grass that deep. Six to twelve inches down is where decomposition happens.

I know your back will protest, but if you can remove, kill and chop the sod, add your soil, then incorporate the "ex-sod" back into the top few inches of soil, that would leave you with a really healthy starting point.

Also, unless you have really long arms, I'd make the width of the beds only 3 to 3.5 feet. Mine are 4 feet, and I find it hard to reach into the middle.

Also, don't scrimp on the distance between the raised beds. Make the path wide enough for a wheelbarrow.

Hope this helps. Good luck.

    Bookmark   April 4, 2009 at 8:24PM
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tambo747(5 Canada)

Hi Stuart :)
Thank you so much for responding! The previous owners had created the original raised bed which I will be duplicating in the opposite corner. I have done the same as you with the exsisting bed. Each year I add a good quality soil/compost mix and my bulbs, rose bush, and hybiscus seem to like it. I believe the previous owners built the bed exactly as you have done. I will follow your instructions! I can't wait to start!!! My back is very happy, thank you :) I'm interested in which roses you have growing? Do you have any tall shrubs that actually do well in clay soil? I'm in Montreal, so anything that is sucessful in your area would work for me too.
Thanks again for your time and helpful advice. Haappy gardening!
Cheers, Tammy

    Bookmark   April 4, 2009 at 8:57PM
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tambo747(5 Canada)

Hi Bev,
Thank you for responding! I really love these forums and appreciate experienced gardners sharing their knowledge!
I intend on digging up all the sod. I dug up 2 areas last spring for my clematis and peonies, and the sod was easy to dig and lift, can't say the same for the clay though. I agree about the nutrients/minerals in the clay.
I am being careful in my plant selection this year and trying as much as possible to choose plants that are tolerant of clay soil, so they will grow happy over time.
I was under the impression that the purpose of land scaping fabric was to prevent weeds from growing in the bed?
I also agree with the width issue. The existing bed was only 2 feet wide, but I went crazy last spring and bought way to many bulbs and plants while forgetting about the bunch I already had that needed to be moved and transplanted. That meant I had to enlarge the bed. It's important to me that the two beds be symetrical so I going to try and plant strategically making room for my little feet to get around.
Thank you again for all your wonderful advice. It is much appreciated.

    Bookmark   April 4, 2009 at 9:16PM
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Hey Tammy - I will gladly share rose and plant varieties that I have incorporated into my raised beds (look for that in the next few days or so)!
I agree with Bev W above - the landscape fabric and the gravel are not a must, but I used them anyway. And also agree that you should only make them as wide as you can reach (I can access the big beds from all sides so the width was not an issue for me).
I have:
(1) 12' x 4'
(2) 4' x 8'
(2) 2' x 14'
I plan on posting photos as well on this site, so stay tuned! Would be glad to offer any advice I can but it sounds like you have success with some existing beds - good for you!
I think my email is on my profile, so you are also welcome to drop me a line there if you wish.
It will be nice to keep in touch and share gardening exploits!
Cheers, Stuart... : )

    Bookmark   April 4, 2009 at 9:24PM
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re: landscape fabric. With two feet of soil in it, not much except really aggressive rhizomes will enter your raised bed. Bindweed and twitchgrass for sure, if you have them. I wouldn't worry about it, really. The benefits of having your native soil in direct contact with the "fake" soil outweigh any potential weeds, IMO. You want the microherd in the native soil to move into your raised beds. Much better for long term soil health.

    Bookmark   April 5, 2009 at 7:04PM
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I do agree that it's unnecessary to dig up the clay soil since this is a 2 ft raised bed. In time earthworms and shrub roots will do the job of breaking up the clay layer. One thing to keep in mind - get plants that are tolerant to cooler zone. In any tall raised beds, the roots of plants are more susceptible to winter freeze and thaw cycles. So if a plant is borderline zone hardy - it will require more protection than other hardier plants.

As for the weed barrier. Landscape clothing is totally unecessary. The only thing I can think of is grass entering the area but because this is a deep bed, it' unlikely it will successfully invade. However if you still have concerns about any invasive plants from without or within the bed (for instance if you planted raspberry canes), you could prevent invasions by putting in a lawn edger inside the bed, before the soil is added. This is a good thing with lower beds and I did this to a bed because the area it was in was constantly being flooded during a deluge... Again, in my opinion. It's unecessary for a tall bed and you can kill off invasive grass by spraying vinegar on those pesky grass.


    Bookmark   April 5, 2009 at 7:27PM
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tambo747(5 Canada)

Stuart, I'll definately stay tuned and would love to see pics of your beds!
Bev, thank you for the explanation. I think if it's better for the overall health of the plants, I'll skip the landscape fabric.
Ianna, you are such a wealth of information. You have responded to my posts before, and I appreciate your advice and you sharing your experiences with me.
This bed will be between 1-2 ft high in a shady/semi shady corner. Great advice about the zone. I thought I was in zone 4, but I went to my local garden center today and they said we're zone 5, so its perfect. All of my plants are for zone 4 or colder!!! I'd like it to be full of lush foliage, lots of texture, and of course color too!
I'm so excited,I can't wait to start!!!

    Bookmark   April 5, 2009 at 8:52PM
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Hey Tammy...Just wanted to check in and see how the raised bed building went...and what you planted?
We are very slow starting here in Calgary, and even this weekend we are suipposed to have a lot of rain and maybe some overnight snow on Saturday! *sigh*
I was away for 2 weeks in May, and have only started to assess my raised beds - everything survived, but may have a bit of a setback this weekend if it cools down too much!
Drop me a line if you wish - it would be great to know how you are progressing!
Happy Gardening!!!
Stuart... : )

    Bookmark   June 4, 2009 at 5:29PM
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tambo747(5 Canada)

Hi Stuart,
Snow... @#!$%* snow in June! Although we didn't get snow in Montreal, up until this weekend it was bitterly cold with regular frost warnings, lows hovering between 0 and 4.
The raised building went well. It is not as high as I would have liked it. We ended up calling a company to do all the digging because I hurt my back at work in Feb. It was nice to not do all the digging, but the price structure goes by vloume in the truck and I couldn't afford to dig as deep as I wanted. I still need to add at least 6-10 more inches of soil to the entire bed and that will make a difference. I'm just waiting for the compost to do its thing.
It's shade on one side and 3/4 sun on the other so I am experimenting with plants. I've been looking for "bones" to put along the fence on the shaded side, but am having difficulty. I really don't want foxglove!!! I bought a clematis for the shade (duchess of edinbourgh) but planted it on the sunny side. Momentary brain freeze due to the @!#$%! cold spring we had. All in all I am happy with it. All the plants in it are new so I'm already lokking forward to see it take shape next year. The beautiful and addictive thing about gardening is that it is never finished! I love that!
Here are pictures:

I will do a hot, full sun dance for you and your fellow gardeners in Calgary :) I hope the weather shapes up for you. and that your garden flourishes!
Take Care!

    Bookmark   June 6, 2009 at 8:53AM
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tambo747(5 Canada)

I forgot to tell you what else I planted...
Well I went for the fail-safe shade plants like hostas, astible, and bleeding hearts. Actually, each side of this bed does get some morning and some afternoon sun (with the exception of the back corner-FULL SHADE ALL DAY), I went ahead and planted some coneflowers and transplanted daylilies that were taking over. oh ya, I also bought a fun hibiscus plant called disco hibiscus. Hopefully it will bloom this year!
Let me know if you have any ideas and what's going on in your garden!

    Bookmark   June 6, 2009 at 9:57PM
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Hey Tammy - well we finally (on June 7!!!!) got all our plants in the pots on our deck! We just had to draw a line in the "frost" and take the chances that the weather was going to improve. Overnight lows have been +2C to -3C and my back has been killing me lugging around heavy terracotta pots full of "stuff!"
I finally introduced some mini roses, herbs, and gerbera daisies into my greenhouse, as well...I relocated my greenhouse last year to a shadier spot at the bottom of my garden - with the temp now balanced better, I can introduce more things. I had it in full sun in the previous years and it was a struggle to keep the temp below 35C - nothing lived!!!
I also started some sweet peas, freesia (I try every year), and evening primrose - so we will see what happens! If we have an Indian Summer, my growing season (in the greenhouse) can be extended into mid-October. While it is a bit late to start some seeds and bulbs, I always remain hopeful (and am occasionally rewarded with success).
I will be working on my raised beds this weekend, and will be introducing some perennials (Golden Creeping Jenny, various thymes, etc) to give some colour amongst the roses and ninebarks - all 38 of my roses survived their wintering, but I may have to replace a few that went a little wild near the end of last summer (some stalks had thorns that would have rivalled medieval war clubs!).
Now that I am finally getting into the spirit of things this season, I will be updating photos (on my blog and uploading some here) - I will gladly share photos and exploits with you!
Your raised bed looks great - and I love hostas, astilbe, coneflowers, clematis...sounds lovely!
This weekend I will perhaps be buying a clematis or two - perhaps a honeysuckle and virginia creeper to grow up and over a pergola I built last year - so many things, so little growing season!!! : )
I may even be brave and try some coral bells this year! There are so many beautiful types (see link to a nursery that shows many examples).
You might have more success than I because your zone is a little more forgiving!!
More later, Tammy! Take care...

    Bookmark   June 11, 2009 at 2:00PM
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Hello everyone, I just happened to come across this today. Check out the Hosta Forum, there is a lot of info on starting new beds. Mow down weeds and grass, maybe spray them with something (if you wish),I use vinegar, salt and dish detergent, then place approx. 10 layers of newspapers overlapped,(some use wet cardboard) enough to cover the whole area, wet newspapers, add soil, compost, composted leaves, manure, etc. lasagna gardening it is called, making layers.

Did raised beds myself approx 6 years ago, poor soil, already mounded by machine,added newspapers, composted leaves and when I planted something I added the others, manure, good soil, peatmoss, more leaves in the planting hole. Added more leaves on top as mulch. Lasted well for 3 years before I had to add more mulch. Beautiful planting soil resulted. The same can be done starting with a flat/or uneven area.

Mine are mainly hosta beds with lots of rhododendrons, azaleas, tree peonies,clematis, a few maples, birches, ferns and daffodils to deter the deer.

Sure saves a lot of work and your back.

Hope this helps,


    Bookmark   June 20, 2009 at 8:41PM
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As mentioned in earlier post, a raised bed may be more subject to low ground temperature in winter. I would think that the materials surrounding the bed might effect this, say thick railroad sleepers versus stone or brick. Perhaps the ratio of h/w/d as well? I am wondering if literally insulating the beds with pink foam/plain foam or such would make a significant difference? It's colder in Edmonton in the wind! Any thoughts welcome (please excuse my veer from the original post!).



    Bookmark   June 23, 2009 at 2:24AM
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