You sound desperate so I will share with you what I did on a new home site when I started my flower beds in Calgary 12 years ago. Holy cow! It's been 12 years!

The builders where we were had added about 10 inches of top soil around the homes. Pretty heavy soil under that. I mixed in just about every thing I could find from bagged top soil and sheep manure to peat moss and potting soil. I did a lot of turning the soil and it turned out good. Everything I planted grew like crazy. We lived East of Calgary on Garden Road. I used to think it was the water-reverse osmosis- but I had the best flower beds in the village and I started many flowers for my neighbours too.We all used the same water. :)

I would guess I went down about 10 -12 inches. Really just juiced it up. I'm sure the Calgarians on this forum have much to share with you. In general I found Calgary soil better than Edmonton. ?

Ginny

Your plants will grow much better if you spend the time to prepare the bed well. That means lots of organic matter and nice loose soil where the roots of the plants don't have to work too hard to get through. I dug out a new bed a couple of years ago and I love working and weeding in it...so much easier than the hard-packed clay of some of my other garden beds.

Thank you, Ginny and Donna!

Donna, how deep did you dig please? I am actually going to get a landscaper to do it (too many beds, too little time!) so I would like to give him very specific instructions.

He said that he would use something called "Garden Party"? Is that good stuff?

Thanks!

We dug down around twelve inches. My husband actually did the work and he only wanted to do about half that, but I insisted and I'm sure my plants are better because of it. We have horrible clay here, and although plants can grow in it, it's a struggle for some. Plants, especially shrubs and choice perennials, are getting expensive to buy...it makes sense to do that little extra prep to give it a fighting chance of surviving in our extreme climate.

Depends how much money you want to spend. Ideally since you have landscapers doing the prep I would have to them remove the top 24" of soil and replace it with good stuff. This will cost a ton of money though and will require a digger on your premises.

Yes, it's mostly clay in Calgary. The Canadian Shield ends around the eastern Alberta border (with a protusion in far north Alberta); the rest of Alberta sits on basically limestone (that's why we have so much fossil fuel here) up to the Rocky Mountains. Parts near the rivers further west (downtown and such) have acidic soil, the rest is fairly alkaline.

You can aim for digging a foot down, but it's really, really, really hard to do with the soil we have.

I'm not a fan of tilling at all. It destroys soil structure. I have found top dressing works really, really well.

Garden Party is a mix of compost, peat moss, manure. It's a product of a local company in town called Ornamental Stone. I've used it before, but it is very expensive. Ornamental also offers just compost for much, much cheaper.

Here is a link that might be useful: Ornamental Stone

Thanks, Donna and shazam! I think that I will probably stick with 12 inches for practical and cost reasons.

So once you dig 12" deep into the soil, do you not have to somehow mix the local soil with the new soil, in order to avoid the creation of a distinct interface between the two soils?

Actually, we got rid of that horrible clay altogether. Maybe your soil is better than mine...I think I could have made bricks with it! If you are keeping the soil, for sure mix it with the good stuff; you don't want the plants to hit that clay and stop growing. I think you only have to worry about large perennials and shrubs though...smaller perennials and annuals won't even get that far down. Remember that the soil will settle a bit after, so you can mound it up.

Donna, when you remove all the clay and local soil and apply the good new soil on top of the dug area, how do you avoid the abrupt interface between the good and original soil? Isn't that something to be avoided?

Ostrich, here's my two cents worth.

I would do a little bit of everything that our fellow gardeners have suggested. I have clay. Horribly compacted clay.

I would dig down 8-12 inches, depending what you're planning on growing in each bed. Be aware that if you dig a big hole and fill it with something else, you're likely to get the bathtub effect. You'll get a big pit of water where you've dug, as the clay next to it doesn't drain well.

I would dig down and add organic matter, such as the Garden Party Mix, and incorporate it with your original soil. If you remove the top soil and dispose of it, the top soil you purchase is likely going to be the same stuff. I would think your best bet after mixing your original soil with the Party Mix, is to top dress with organic matter, and start your own compost pile. That way you can keep adding organic matter.

BTW What type of plants are you wanting to put in these beds?

An alternative would be to do lasagne style right on top of what you have and raise your beds up 8 inches or so. If you chose to do that, I still dig the existing soil if I'm not raising the bed by much.

ostrich,

In Calgary, when you go down 12 inches, you'll hit the subsoil (pure clay and large rocks) :)

ostrich,
I think we took the garden fork and loosened the existing soil, if you could call it that, prior to filling with the good soil. Btw, we took some existing top soil from other areas of the garden and mixed in some peat moss, bagged compost and bagged planting soil. I had stockpiled about 30 bags of planting soil in the Fall (got it really cheap).

We actually expanded the flower bed, dug out about two or three feet in the front. The plants have done really well. You might want to dig deeper at the back and have the front more shallow (of the good soil, I don't mean planting it on a slope). That way, annuals and more shallowly rooted stuff won't be affected by the soil depth.

Thanks, everyone!

Nutsaboutflowers, I plan to plant shrubs (e.g. hydrangeas) and perennials in the beds. Yes, I definitely will need something with a lot of organic matter.

shazam - you have raised a very good point - if I dig too deep, I will hit large rocks and clay anyway! BTW, shazam, where do you buy your mulch from around the Calgary area please? Have you ever ordered from that Ornamental Stone place that you sent me a link for please? There's a lot of great info there on that site - thank you!

Donna, thanks for the tips! Interesting thought about the different depths in the various parts of the bed. Thank you!

I get mulch from Ornamental if I need a lot. If you want to save a lot of money they have reusable 3 cubic feet bags that you can fill up yourself. Mulch is very light so you can stuff your vehicle up to the rafters :) Their montane mulch is, IMHO, the best wood mulch you can find anywhere.

You can get any of their bulk products using the bags, BTW.

Also if you need stone cut, they will do that for you for a nominal fee.

If you want to use compost as mulch, Sea Soil is the best best product, period. Nothing compares. But it's very expensive. You can find it at most garden centres.