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Thick clay under top layer of soil in new garden

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  • FairygirlFairygirl Posts: 55,117
    edited February 2023
    The amount of time it would take to amend that 'proper' manky clay soil for successfully cultivating salvias would be a very, very long time.
    In the meantime, the salvias will have to be kept somewhere else, because planting them in the existing conditions, with the bed of solid clay beneath that topsoil, will definitely be a factor in their survival  :)
    It's a place where beautiful isn't enough of a word....



    I live in west central Scotland - not where that photo is...
  • JennyJJennyJ Posts: 10,576
    It'd probably be better to keep the salvias in pots, at least for a year or two while you improve the soil and get a feel for how wet/dry it gets through the year. If you find that it still doesn't drain well after improvement, you might be better taking @Fairygirl 's approach and making a raised bed for the salvias.
    Doncaster, South Yorkshire. Soil type: sandy, well-drained
  • zugeniezugenie Posts: 831
    I had very similar clay soil at my old house, except without the layer of topsoil! What I found worked was the autumn before I planted; digging loads of compost in taking the time to break up the big clumps and make sure the compost was well in there!! Then in the spring I started planting, the years following the soil was much nicer and easier to dig, and I had lots of happy plants (even salvias!). I would have mulched every year except that it was a large area and was too expensive.

    For smaller areas or if you can afford it, I would do the same and break up the clay and mix compost in properly at the start, I only did a fork depth down, then for the following years do the no dig method and just add the organic matter on top! I love the idea of no dig but I found for clay a hybrid method was best, to break the clay up first!

    definitely keep the salvias in pots for the first year or make a raised bed for them!
  • B3B3 Posts: 27,505
    edited February 2023
    I roughly break up the clay and leave it in large chunks. If I have any, I put spent compost or a mulch on it.  It's usually crumbled by the spring. If not completely crumbled, I tread on it and then jiggle it with a fork or trowel.
    In London. Keen but lazy.
  • Thank you to everyone for sharing advice and experience — it’s really helped me think through what to do, and it’s so nice to hear (and see!) other people's successes with heavy clay 😊 This past week, I’ve systematically dug a large sunny area, broken up the clay subsoil and added as much bark compost as I could afford! I did consider trying to dig it out but it goes way too deep!! Hopefully breaking it up and adding compost will do the trick. After I did that, I used some stones we had to build a low dry stone wall around the area to create a raised bed. It only raises the soil level by about 4 inches, but hopefully it will drain better! I think after this initial effort I will try to run it as a no dig bed, adding organic material every year. In the raised bed is a mixture of the black garden soil on top of the clay and lots of compost. Do you think this is ok for inside a raised bed? The soil is also very aerated at the moment so not sure if I should wait for it to settle before planting.

    Thanks again everyone 😊


  • FairygirlFairygirl Posts: 55,117
    I think your bed will need to be a lot higher than 4 inches  :)
    I'd make it at least a foot, then add as much rotted manure and compost as you can. You can buy bagged manure in GCs etc. If you also add loads of grit, or fine gravel, that will make the process quicker in a raised bed. Not ideal for open ground as you'd need tons of grit for it to be effective. 
    It's vital to have  good drainage for salvias, especially with underlying clay, and yes- whatever you do, the soil will settle, so it needs to be left initially, and more organic matter added regularly.  :)
    My lowest raised beds are around 6 to 8 inches, and some are on top of rubble next to the house extension, but even then, I'd need to keep an eye on the medium if I wanted salvias in them. Most of those lower beds are in shade and  have plants which like damper soil.
    I only grow the reliably hardy salvia [caradonna] as they aren't very well suited to my conditions, but I grow other plants which need good drainage, and that's the approach I take with the beds they're in.  :)
    It's a place where beautiful isn't enough of a word....



    I live in west central Scotland - not where that photo is...
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