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How much topsoil to add on top of clay?

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  • FairygirlFairygirl Posts: 55,117
    If you want that sort of planting, it would better to add/mix lots of compost into the soil over the clay, once it's improved with manure etc. Raised beds will also help them survive and thrive simply because they drain more easily.
    Otherwise, yes - they could struggle quite badly. 
    Most of my raised beds [differing heights etc]  have largely compost as the main component, with turf in the bottom of the bigger ones. The soil there is now suitable for plants that need good drainage. The ones facing north-ish have nothing much added other than a bit of compost when a plant is put in, or added as a mulch to improve the structure.The plants are then suited to the site/aspect.
    The garden was slabs and gravel on compacted, soggy, sticky clay, which is why I put raised beds in for the bulk of the planting. The borders I created along the boundary  at ground level [formerly just grass] had manure laid on top of the soil, once that turf was removed for the raised beds. That was left to work on that soil, then planted  the following year, with mainly shrubs and sturdy planting that could cope with the rainfall. I didn't add much else until the soil became workable there.  :)

    It's a place where beautiful isn't enough of a word....



    I live in west central Scotland - not where that photo is...
  • Busy-LizzieBusy-Lizzie Posts: 24,043
    When I moved house and made the garden 3 years ago in SW France I found that the soil was clay. I didn't have homemade compost so I bought sacks and sacks of the cheapest compost, added some blood, fish and bone fertiliser to it and dug it all in. It made a huge difference and I have grown the plants you mention, but the weather is warmer than the UK. Each year I mulch my beds but don't dig anymore.
    Dordogne and Norfolk. Clay in Dordogne, sandy in Norfolk.
  • KT53KT53 Posts: 9,016
    Digging anything into clay can be problematic.  My mother's garden was clay and it went from being undiggable because it was too wet, to undiggable because it was too dry, with only a window of a week or so to be able to dig the stuff.
  • Get lots of organic matter and dig it in, that will cure it.
  • punkdocpunkdoc Posts: 15,039
    Why dig when the worms will do it for you.
    How can you lie there and think of England
    When you don't even know who's in the team

    S.Yorkshire/Derbyshire border
  • FairygirlFairygirl Posts: 55,117
    KT53 said:
    Digging anything into clay can be problematic.  My mother's garden was clay and it went from being undiggable because it was too wet, to undiggable because it was too dry, with only a window of a week or so to be able to dig the stuff.
    Just adding it on top is the best way @KT53, but it can take a little while to get worked through by worms etc. I've never dug it in. For bare ground, doing it in late summer/early autumn is the best time, just because it's then easier to wait for spring to do that planting. Any shrubs or trees can still be done at the same time, as long as the manure isn't fresh. 
    It does mean you have to wait to get planting done, but that's gardening eh?   :)
    It's a place where beautiful isn't enough of a word....



    I live in west central Scotland - not where that photo is...
  • LoxleyLoxley Posts: 5,698
    You could look at what Dan Pearson did at the Delos Garden (Sissinghurst). To create a Mediterranean garden where previous attempts had failed on Wealden clay, they built low walls and tipped lots of free draining material with lots of grit, crushed brick and sharp sand. No manure: this sort of planting doesn't want manure.

    The solution was not to amend the clay, but create a new free draining substrate over the top of it. [You can downscale the idea for a smaller garden of course]. I only suggest this as your question was about adding material on top of existing clay, which is what Dan did here. Improving the clay soil and adapting your planting palette is the traditional approach and also works.



    The gardens south-sloping ragstone terraces
    "What is hateful to you, do not do to your neighbour". 
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