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Building up a border on a clay base

pbrown1907pbrown1907 Posts: 2
edited May 2021 in Garden design
Hi all,
Very amateur gardener here, but looking to learn some tricks.
Currently, all around my house I have no area where I can grow a garden.  Out the front it is all tarmac-ed with hedges along the boundary and a small stone covered area, and out the back it is mostly raised decking, with a side area stone covered up to a smaller area of decking.  This side area is the only place I could possibly create an area for some flowers (that are not in containers).

Along this side stone covered area runs a hedge and wall (the decking has a fence that ends at the hedge).  I am wanting to dig up the stones along the hedge and wall and make a border that goes up as far as my decking, say around a foot and a half out.  I have quickly dug up a small area at the edge of the wall to see what lies beneath and it looks like under the stones there is a clay soil.  I haven't dug in front of the hedge yet.  The area is pretty much always in shade, if it gets direct sun its very seldom throughout the year.  Ideally I would hope to plant something like lavendar under the hedge (as I've been growing this in pots up to now there), and some sort of climber at the wall.

How would I go about making this border on top of the existing clay soil?  Would it be better to build up more of a raised bed than simply a border flush with the remaining path of stones?  Any help would be greatly appreciated!
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  • PosyPosy Isle of Wight.Posts: 3,601
    Hello and welcome. I think a photo of the area would be really helpful. There shouldn't be any problem improving your soil and you could keep the bed level or raise it as you wish. You will need to choose plants that enjoy shade and heavy soil so not lavender, I'm afraid but there are many. 
    Your soil will need a good dig over, adding well rotted organic matter, loosening it up and letting in air and water so that it turns back into a healthy growing medium, then you can start looking at what sort of plants you like. There's lots of advice on here about planting shady areas, too.
  • pbrown1907pbrown1907 Posts: 2
    Hi Posy, thank you for your reply and welcome. Here is a pic of the area, today is very sunny so shows nicely how much shade it gets.  You can see a sleeper there under the white container, it would be roughly that up to the decking.
    How long would you say it would take to get it back into a healthy growing medium, before I can start planting?
  • PosyPosy Isle of Wight.Posts: 3,601
    Well! Depends what you find underneath. The ground is likely to be compacted and may contain rubble or stones. You cannot know the depth, yet either. The key thing will be to remove big stones, bricks, rubbish and so on, and then have a good look. If it is heavy clay it is well worth digging down a bit to find out if there is a 'pan' - a solid layer of clay that will prevent drainage. You can break this up with your fork, then pile back your soil and muck.
    After that the soil will settle and the level will drop, so give it several weeks of rain and dry or you could find your plants sinking much lower than expected!
    After that, you're good to go, I should think.
  • ObelixxObelixx Vendée, Western FrancePosts: 28,587
    Are you wedded to the idea of keeping all that decking?  Do you need that much space for a seating/dining area?   I would be inclined to remove some of the decking to create planting space.

    However, the first thing you need to do is clear the area you initially want to plant removing stones, any weed membrane, rubble and rubbish and checking there is no further impediment just below such as drains, concrete or whatever else builders hide.  The next thing to know is that clay is inherently fertile but its particles are so fine it will not drain well when wet and will dry like concrete when there is no rain so you need to open up the texture.

    The best way to do that is to fork it over and break it into clods then break up the clods if you can to a smaller size and then pile on a deep layer of well-rotted manure and/or garden compost.   There's no point hurrying this phase as the more organic matter you can get layered in the clay, the faster it will break down and become more manageable.  Adding further layers of garden compost, manure or bought in soil conditioner every autumn will also help.  The worms and other soil micro organisms will work it in for you over the winter.

    You need to look up plants suited to clay soil and shade and also establish whether your soil is acid, neutral or alkaline.   Soil tester kits are available at garden centre and good DIY stores and are not expensive.   If the soil is neutral to acid you could try camellias but for a smaller shrub have a look at leucothoe.  Both will be much bigger than lavender tho.


    "We don't stop playing because we grow old; we grow old because we stop playing." - George Bernard Shaw
  • hatty123hatty123 West YorkshirePosts: 125
    Fellow amateur here! I created a border last year on top of heavy clay soil. I started by trying to dig it to incorporate organic matter, but found it so heavy, impossible to get a spade in and coming up in such lumps that I quickly gave up! Instead I added lots of manure and compost on top to about 6 inches deep with a board to retain it. In autumn I planted bare root raspberry canes, over wintering garlic and onion sets, daffodils and tulips, all plants that need good drainage so in theory not suitable. Daffodils and tulips did really well, onions and garlic are now nearly ready to pull, raspberries have made a strong start. So don't be put off by the clay, just get plenty of compost on top. I'd be more worried about choosing plants that thrive in shade.
    It turns out I followed the "no dig" method I just didn't know it at the time, I was just being lazy when faced with clay 😂 it's worth looking up, could save you a lot of effort digging if you think it would be appropriate for your border 
  • LoxleyLoxley NottinghamPosts: 4,978
    Raising the ground level with imported topsoil is a good idea, but would that affect the building? You might breach the DPC and/or cause problems with the render. Maybe it'd be better to dig down, break up the clay (which you'd have to do in either case) and lay fresh topsoil into the bed to top it up after removing the stones. If you can go wider than 2.5 feet it will increase your planting options. Lavender isn't really going to like the shade, or the soil, but there are plenty of plants that will do well there.
  • PosyPosy Isle of Wight.Posts: 3,601
    Should have said. It's really important your soil does not touch the house wall.
  • Would agree exactly with @Posy plants will sink if you don’t leave it to settle after digging over heavy clay. I’d buy as many bags of farm yard manure as you can and be generous with it. 
    Lavender is a Mediterranean plant so like lots of sun of gritty soil so I’d put this in a pot in a sunny place.
    Things that I’ve grown well in shade & clay are Dicentra/ hosta/ ferns/ bergenia/ lady mantle/ hydrangeas/ pyracantha/ viburnum 👍
  • Butterfly66Butterfly66 BirminghamPosts: 767
    Clay soil is hard work but good as it holds nutrients very well. I would follow the advice on how to improve it (which is about making it easier to work than anything else) rather than importing in topsoil
     If you have a garden and a library, you have everything you need.”—Marcus Tullius Cicero
  • LoxleyLoxley NottinghamPosts: 4,978
    Clay soil is hard work but good as it holds nutrients very well. I would follow the advice on how to improve it (which is about making it easier to work than anything else) rather than importing in topsoil
    Yes, but the stones and harcore need to be dug out and replaced with something.
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