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Creating new flower beds - question on soil

I moved house a few months ago and am just starting to create a new flower bed in a good size south facing garden. I had thought (see other posts!) that I had been blessed with amazing soil... however once I started properly digging what I discovered is that the first 30cm is top soil, then beneath that is a layer of rocks. I don't mean "it's a bit stony" I mean there's a small amount of soil in between a layer of large gravel like rubble. I suspect that when the house was built in the 1950s that they laid a layer of hardcore before the top soil in order to level it out, as the immediate surrounding area is very hilly yet my house/garden and the neighbouring are suspiciously flat! (Although before these houses were built this area used to be called Stoneyfield Common - clue is in the title perhaps!)

(Side note: I also discovered about 50 broken bricks and two broken clay drainpipes buried under my new flower bed that the original builders had helpfully buried)

My question is - how much is this many rocks going to affect my ability to have decent plants? I've already set about the task of removing as many of the large stones as I can down to a depth of about 2 foot. It has been back breaking and arduous! Is this necessary / will it make a difference / am I wasting my time or is it worth it? My plan is also to mix in mushroom compost. If I didn't try to disturb the "below top soil earth" and get rid of all the rocks/stones, I wouldn't be able to mix much in as the top soil really is only down to about 30cm.

Any thoughts gratefully welcomed!


  • PosyPosy Isle of Wight.Posts: 3,600
    I don't think that 30cm is enough for planting into if the plants cannot get their roots down any further. The soil may dry out very quickly, too.
    I feel that your options are either to build the soil up by edging your beds and filling up with topsoil or digging out stones, an area at a time. It's really hard work, as you say, but that's what I would do. Good luck!
  • B3B3 South East LondonPosts: 23,621
    edited February 2020
    Do you know how deep the rubble goes and what is under it?
    In London. Keen but lazy.
  • gilla.walmsleygilla.walmsley Posts: 253
    edited February 2020
    @Posy I suspected you were right, I just wanted to sense check that I wasn't wasting my time! I moved into the house in September and it was difficult to tell as the whole garden was just lawn but I remember it being baked solid dry and the grass was like straw. I think you're right and it really doesn't get much moisture at all. I've never worked with dry soil before so I'm going to need to read up on plants and I guess commit to a lot of watering!! Do you know have any idea how far down most plant roots go? I know that's a wide question and obviously trees will go much deeper, but on average for standard shrubs and perennials?

    @B3 from what I can make out, the layer of hardcore is approx 30cm deep and then underneath that it's just original soil, which is also naturally very stony - the Soilscapes website tells me I am number 7 (freely draining slightly acid but base-rich soil). I have managed to remove the gigantic pile of bricks and drainpipes that had been buried there - at least the pile that is under where my new flower bed will go, who knows how much more there is under the rest of the garden!
  • PosyPosy Isle of Wight.Posts: 3,600
    Crumbs! That's a job and a half. I don't honestly know how deep roots are, it varies enormously, but even shallow-rooted annuals will struggle for moisture. If your base soil is good most plants will cope with stones and you can add lots of muck before you plant, and mulch after, which will reduce the watering a bit.
    I feel very useless, because my ground is dense, waterlogged clay, slightly alkaline,  so all my experience is about improving drainage, although I also have the depth problem in that there was very little top soil. Good luck! When I look at mine I try to remember that what doesn't kill you will make you strong!!!
  • @Posy I have only ever worked with horrible clay soil before so I feel your pain - my previous tiny garden was a sloping swamp of clay, I tried to add so much grit in the 5 years I was there - didn't make a blind bit of difference :smile:  I'd have longed for all these stones then! I'll carry on working my way through now and do the best I can do  - fingers crossed its enough! Thanks for all your help
  • FairygirlFairygirl west central ScotlandPosts: 47,960
    Manure is the best additive for improving either heavy wet clay soil, or poor thin stuff.
    There are no short cuts unfortunately. Do a bit at a time, one area at a time, and be prepared for a lot of graft. 
    The alternative is raised beds, using sleepers, rendered block walls, stone or similar, and that depends on your budget and/or DIY skills  :)
    It's a place where beautiful isn't enough of a word....

  • B3B3 South East LondonPosts: 23,621
    I suppose you could use the bricks for your raised beds!
    In London. Keen but lazy.
  • I think cost will prevent me from going for raised beds - it's quite a large garden and there will be a lot needed! But i haven't got rid of the bricks (or the drainpipes!) and I'm determined to find some use for them or way to incorporate them into the garden! @Fairygirl I'm ok with hard graft - as you say, I'll just do a small bit at a time. No idea how I'm going to dig the pond I had planned though - might need to hire some kind of equipment help than just my spade!
  • FairygirlFairygirl west central ScotlandPosts: 47,960
    Ach - just eat a bit more spinach @gilla.walmsley- you'll have Popeye arms before you know it  :D
    Could you investigate a local handyman, to see what it would cost for some simple timber beds? [the pond too perhaps] I did all mine with fencing timber, and if you get it from a builders' merchant it's far cheaper.
    Mine are all different in height and size, to work in with the fences, and they have a top edge to make them more decorative. The timber worked out at about £1 a metre at the time [7 years ago] and I used a few bits of fence posts concreted in for the corners etc. 

    Your bricks and drainpipes can be used for a little wildlife area - places for insects etc to hide away. The drainpipes would be very useful for cover at the pond too - frogs love a wee damp, dark place to hide in. I use bits of broken terracotta pot in various places for that :)
    It's a place where beautiful isn't enough of a word....

  • I think perhaps all is not as bad as you fear and you would be better working with the conditions you've got instead of getting involved in major groundworks. In most gardens, the top 6″ of soil contains the most nutrients needed for plant growth. This is because most root growth  occurs in this relatively shallow depth. (Think about the depth of tomato grow bags for example) Also consider the relatively shallow depth of large plants in garden centres pots, which of course have their lateral growth restricted by the pot.

    Most common problem as you've seen from other posters is the opposite one of clay soil/poor drainage. Most plants need good drainage which you've got!
    You could offset the problem by a) applying generous manuring to improve water retention and nutrition in the top layer as suggested above. b) committing to frequent watering c) applying pelleted fertiliser/organics regularly. This will offset the high levels of nutrient leaching you will inevitably experience.  
    The soil added will gradually bed down into the hardcore below and you can add to it each season. 
    Maybe try out on a manageable area this season before committing to major planting schemes. 
    Of course, this would not apply to trees or especially deep rooting plants/veg. But then you could focus the heavy lifting on those planting areas only. 

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