Concrete layer in flower bed area - what can I do?

Hi - I'm a first time gardener, (my only experience to date is a few pots of gerianiums outside my front-door.) I'm trying to create a flower bed around the perimeter of my lawn but yesterday I discovered a layer of concrete in the flower bed area about 5-6 inches down!!!! - so now I'm a bit worried that this area will not be deep enough for a flower bed. I want to have a mixed border with mainly evergreen shrubs, 3-4 azealas /camelias, maybe a hydrangea but also room to plant spring/ autumn bulbs and summer /autumn perennials so that they come up in between the permenant shrubs and plants.

Because of the concrete, I'm now thinking I may have to resort to building a raised bed, so I'm trying to work out how deep this will need to be. I've read that rhodendrons have shallow root systems and that they don't go too deep (so I'm assuming azealeas don't either) but I can't find anything to tell me what will be 'deep' enough to accomodate the root systems of the plants I want to grow.  Would another 7" be enough to make the entire depth up to 12 inches?

If I do have to create a raised bed then I'll do it with wood or sleepers as I've used sleepers elsewhere in the garden and don't want to have too many different materials in the garden but then again I don't want to use too many sleepers and make it too high as I don't want the structure to be too dominant as the garden is small and I need to make a L shaped border. So I suppose my question is do you think I would get anyway with just one sleeper height above the ground so that the entire depth is then raised to 12 inches ?

I don't think that's deep enough for the selection of plants that you mention - there won't be enough of a water reservoir in dry periods, while in wet ones it may not drain. There's also the issue that rhododendrons like acidic soil, and concrete is alkaline.

Is there no way that you could explore how deep this concrete is with a view to removing at least some of it?

I think you need to establish first the reason for this concrete-is this a solid layer or just bits of concrete as in builders rubble?

What is the possibility of getting it out?

Hi - thanks for your replies. What would you suggest as an ideal depth for this type of planting?

I'm going to investigate the area a bit more tonight with my husband. The house is an old cottage c1890 and in the area to the side of the planned flower bed there is a lot of concrete about 4m2 outside the kitchen door however it stops before the lawn area which is why we thought we could have the flower beds around the lawn in front of the existing mature hedges. I suppose as there is mature hedges growing in that area we never assumed that there was concrete there too. It was quite a surprise yesterday when I found it.  The area outside the kitchen door was a gravel area when we bought the house last year  (so we don't know the history of it) and we only discovered the concrete there when we lifted the old gravel , just as well we are only planning to replace the old gravel with new stuff to freshen the area up. 

We have an area of concrete, the size of two old cottages, so fairly substantial. Some of it we have gravelled and use as a seating area in  with a Gazebo. However, the rest I coverd with top soil, held in place by large boulders, so in effect a raised bed. The soil depth is about 18 inces or so. I have filled it mainly with herbaceous stuff. Round the edge of the gravel area I planted Bamboo and Miscanthus of a giant form. the concrrete has stopped them from becoming too invasive.

We did find another area which had a concrete base of about 2m by 1m. We guessed that it was the base of an old outsoor toilet. No drains, just a bucket to be meptied onto the garden eventually. That we did remove. Underneath it was a huge mass of small boulders. I used them to make the raised beds. Even worse was the area in front of it had a deep pit which was where the cottagers had put all their broen glass and potters. I only managed to clear the top 2 feet of that and it was still gong down. Hope you area is just the base of say a coal bunker.

As it's an old cottage it is possible that the concrete is to cap a well if it's close to the kitchen.

I would echo MuddyFork's thoughts - I've lived in several old houses that have capped wells near to the house.  You might even be able to make an attractive feature of it,

It could be a capped well and worth investigating. Is it possible a garage has been there, one took up a large part of my garden, I had to remove a concrete garage base, concrete path and concreted bar-be-cue area before planting, fortunately I bought the house as seen so knew what lay ahead.

One section does remain, the concrete was just inpossible to break up and it's to the side of the garden about 2ft by 4ft with 8inch of soil on top, nothing has ever grown there, even a lawn and grass refused to grow so I sited a compost bin on top, best compost I've ever had.

Agree with Geoff you need to check it out.

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I  have just moved into a flat with a small garden that looked as if it hasn't been touched all the time it's been here, about 30 years.  The soil was impossible but there was a natural raised bed at the back, with a retaining wall.  I just filled that up with compost/manure, planted that and put weed control fabric and bark mulch on the rest, with lots of big containers.  It does look really pretty now.  You can add your own personal touches, like a water feature and a few small raised beds here and there.  It doesn't have to be all planted.

Thanks again for your replies.  It's great to get a different take on things and advice.  The total area of concrete is about 16sqm right outside the kitchen door, might have been a well at some point, am doubting it was a garage as there is no access from the street and it would have obstructed all the windows to the front of the house.  We plan to gravel over the majority of the area. The actual 'problem area' in the flower bed is only about 1.5metres x 0.5m, so at the moment we are trying to break it up with a pick axe, if this doesn't work then we will make a raised bed over it.  Thanks again for your advice.  I'm sure I'll be back to the forum, as my gardening journey continues.

Breaking up concrete with a pickaxe is very hard work. I have done it. If you can try to make a groove along the line where you want to leave the concrete in situ. Hammer and stone chisel would do it, but an angle grinder is better. Then try to get a crow bar under the edge of the bit you wish to break up and then hit the concrete with a sledge hammer. It breaks easier that way. And the groove, cut should stop it going past where you wish to retain it.

Otherwise you are into hiring a pneumatic drill. Donr that too.

Best of luck with it.

Hi Berghill - yes we are finding that out.  Thanks for the tips - I'll pass them onto my husband. 

Re: depth -  if we can make the flower bed area at least 12" deep does this give the plants a good chance of success?  

 I'm also going to replace the existing soil in the area with a high quality top soil, lay weed membrane and mulch.  I'm also thinking of potting up the acid-loving plants in a pot with appropriate soil first before I 'plant' them in the flower bed to mix in with the other plants. This may sound a bit crazy to somepeople but I really want the flower border to have the ' planted' look rather than pots everywhere.  Not that I'm against container plants in any way  I do plan to have some at the doorway, I just don't want pots everywhere.  I suppose its got something to do with years of living in flats and yearing for a garden to plant things in and then finally getting a house with a garden and then finding out that I can't plant after all and have to go back to pots!

!2 inches of good soil would be sufficient for most herbaceous things, but probably not shrubs or trees. You might find that they dry out more quickly though, so you would need to keep an eye on that.

Our soil is so contaminated with lime mortar that we have never bothered trying to grow acid loving plants so cannot help on that score.