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Site for new bed is full of builder’s sand, what to do?

NollieNollie Posts: 7,529
in Problem solving
I’m preparing a new rose and shrub border and it seems to have been a dumping ground for a ton of builder’s sand. The soil underneath the sand is a thin layer of compacted clay on rock so you can imagine the challenge..

I’m digging in loads of manure and woody compost to try and break it up, as I normally do with my clay soil, but as it’s a raised bed by necessity (to gain some planting depth) It will end up filled with roughly a third clumpy, sandy stuff and two thirds added material. 

I feel I need to beef up the ‘soil’ ratio to provide a decent amount of long-term fertility, but the only ‘top soil’ available here is clay- based and pretty heavy. I can’t decide if that will make it better or worse!

Any thoughts? 

Oh and apart from the inherently evil combo of clay and builder’s sand, does the latter actually have any saving graces, such as nutrient benefits? 


Mountainous Northern Catalunya, Spain. Hot summers, cold winters.
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Posts

  • PalustrisPalustris Posts: 4,307
    Is this sharp sand or the soft red stuff used for making mortar etc?
  • Hostafan1Hostafan1 Posts: 34,889
    my last garden was a 12" layer of builders' sand. I just added tons of compost over the years.
    I can't tell you the joy when i found my first puddle
    Devon.
  • NollieNollie Posts: 7,529
    It’s sort of reddish yellow, @Palustris, don’t think it’s sharp as it’s bonded with the clay, I’m breaking up hard sandy lumps.

    That’s reassuring @Hostafan1, more compost I can do!

    I do worry there is little oomph/long-term nutrient value for hungry roses and shrubs though but don’t know of there is anything I can add to improve it. Adding clay topsoil seems counter-intuitive but the only thing I can think of at the moment.
    Mountainous Northern Catalunya, Spain. Hot summers, cold winters.
  • PalustrisPalustris Posts: 4,307
    edited October 2021
    All you can do is as Hostafan says, add organic material and even more organic material. One of our gardens was on a south facing sand dune. Over the 12 years we were there we added lorryloads of manure from a farming friend. Even then we rarely found a worm and the manure disappeared into the 'soil' without trace.
    Best of luck with it.
    It may be worth adding some Lime (Gypsum or dolomite is best) as that does make the clay easier to use.  It works by making the clay gains stick together, Flocculation is the term to look up.
  • NollieNollie Posts: 7,529
    Well it’s not as bad as a sand dune @Palustris, that sounds like a nightmare. It’s more the fact there is so little soil and most of that is the dumped sand, so by the time I fill the raised bed, the shrubs and roses will be growing in mostly manure and compost. It’s already off the scale alkaline, (as is my well water) so adding lime would do more harm than good, I think. Especially to the roses that already get chlorotic here.
    Mountainous Northern Catalunya, Spain. Hot summers, cold winters.
  • PalustrisPalustris Posts: 4,307
    At least then adding organic material should reduce the alkalinity of the substrate as compost is acid. 
  • NollieNollie Posts: 7,529
    True, yes the compost I use is acid and it does help to buffer the alkalinity a little. I pile it on annually to all the beds. Probably balanced out by the alkaline manure though 😆 
    Mountainous Northern Catalunya, Spain. Hot summers, cold winters.
  • FairygirlFairygirl Posts: 55,117
    Do you have the facility to make leaf mould @Nollie? That would also help. 
    It's a place where beautiful isn't enough of a word....



    I live in west central Scotland - not where that photo is...
  • NollieNollie Posts: 7,529
    Oh idiot that I am, @Fairygirl, I have several sacks of it around the back of the shed I had completely forgotten about, so thanks for reminding me, I will add that today, cheers 😊 
    Mountainous Northern Catalunya, Spain. Hot summers, cold winters.
  • Chris-P-BaconChris-P-Bacon Posts: 943
    Nollie said:
    It’s already off the scale alkaline, (as is my well water) so adding lime would do more harm than good, I think. Especially to the roses that already get chlorotic here.
    Soil pH can't be altered. Well, not significantly and certainly not long term. You'd be wasting your time trying. 
    Work with it instead. Add much organic material and plant accordingly would be my advice..although not roses. 
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